# How to drop compression of a GTO 389



## extinctmake (Feb 8, 2011)

Hi all, this is my first post to this forum. I own a frame-off restored '65 GTO convertible that I completed a little over five years ago while owning the car for over 25 years.

My car is equipped with the correct WT-code 335-horse 389 with the correct Carter AFB (3895S) and a Muncie 4-speed transmission. Many years ago, as a 19-year-old pimple-faced kid with my then run-down GTO, I bought this engine from a machinist I was acquainted with (now friend who's since retired from doing machine work) who built this engine for his '57 Pontiac street rod. It was the first part I bought for my GTO. The engine has a compression ratio of at least 10:1 and is likely closer to 11:1. 
The engine runs well for a stocker. He re-curved the factory distributor to give full advance at 3,000 rpm. The engine runs the factory grind 067 cam, but it has the poly lock rocker arm nuts and a couple of other tricks like a port-matched intake manifold.

I didn't mind the need for higher octane fuel for this engine since I don't even drive the car 1,000 miles a year. At the time the high test was $4-%5 a gallon. Now it is $8 and I don't anticipate it ever going down in price. Sometimes I mix Amoco Ultimate with the racing gas and most of the time it seems to be okay. It will ping a little once in awhile. It never does if it drinks the 100 octane straight.

This situation brings me to this forum for some sound advice and information. I have the actual, numbers-matching WT-code 389 to my GTO. It needs to be completely rebuilt and hopefully the block, heads, crank, etc. is rebuildable. I think it is. My goal is to build my engine as close to stock as possible with the ability to run on the same fuel as my 2002 Silverado. I want the car to perform well, but I'm not going to race it. I just want it to run like a 1965 GTO is supposed to run. I'm looking at using Sealed Power (Federal Mogul) parts and plan on selecting its standard cam rather than some race grind. I like the low end torque of the mild standard cam and I want a smooth idle. Again, I'm not headed for the drag strip with this car. It just needs to remain fun to drive and responsive on the street.

I met someone at a car show last summer with a '64 GTO who made his engine run on low octane fuel by having his original 389 rebuilt using standard-sized 400 pistons and having his 389 block bored .060 to achieve a 4.12 bore like a standard 400. He says his compression fell to 9.2:1. 

Is this true? Is it safe to bore a 389 .060 over without causing overheating? I had my original radiator re-cored with a four-row core and I run mild 3.23 gears. My car is barebones with no power options, so maybe it wouldn't overheat. I typically would bore my block just .030. I suppose I could try and find some dished 389 pistons. I want to retain the original #77 heads for originality.

Would I need to alter the combustion chambers of my heads to accommodate a 400 piston?

Will the 400 pistons require any modification?

Which piston rings should I use? 400 standard size rings, or .060 389 rings? Maybe they are the same.

Is there any tricky machine work required to build my engine this way, or will the parts go together as if it were a stock 389?

Thanks for reading my long-winded entry and I appreciate your input.


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## Instg8ter (Sep 28, 2010)

how many miles on the engine? To keep originality all you should have to do is have your new pistons dished to achieve around 9.2:1 with your existing heads for standard pump gas. Lunati is making some nice cam kits for the pontiacs from mild to wild. Should only need to bore it .020 - .030 for a re-build, since you are looking for stock + performance. I am sure some of the engine builders will weigh in with more specifics. welcome to the forum EXT...:cheers


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## freethinker (Nov 14, 2009)

extinctmake said:


> Hi all, this is my first post to this forum. I own a frame-off restored '65 GTO convertible that I completed a little over five years ago while owning the car for over 25 years.
> 
> My car is equipped with the correct WT-code 335-horse 389 with the correct Carter AFB (3895S) and a Muncie 4-speed transmission. Many years ago, as a 19-year-old pimple-faced kid with my then run-down GTO, I bought this engine from a machinist I was acquainted with (now friend who's since retired from doing machine work) who built this engine for his '57 Pontiac street rod. It was the first part I bought for my GTO. The engine has a compression ratio of at least 10:1 and is likely closer to 11:1.
> The engine runs well for a stocker. He re-curved the factory distributor to give full advance at 3,000 rpm. The engine runs the factory grind 067 cam, but it has the poly lock rocker arm nuts and a couple of other tricks like a port-matched intake manifold.
> ...


boring .060 and using 400 pistons alone did not lower his compression. that will raise compression. he must have used dished pistons. you can do that with 389 pistons. i would not bore 60 unless it needs it. it is safe to do so but why go so much on a low performance engine. 
i would consider 389 dished pistons to accomplish your goal of lower compression if you want to keep stock heads.


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## extinctmake (Feb 8, 2011)

Thanks. I'm not really sure how many miles the engine has. When I got the car it was a disaster. The odometer read just under 50k, but it might have been 150k for all I know. I finally disassembled the short block last year because the pistons were frozen in its bores. It seemed to clean up okay, so I think the engine is rebuildable.

I would like to get away without boring the block .060. I'll have to see who makes dished pistons for a 389. 

Would thicker head gaskets create any significant reduction in compression? Another person I talked to at a car show suggested I pull the heads off my existing engine and put in a thicker head gasket to reduce the compression. That sounds too good to be true to me.

At least I'm not in any hurry to do this. I can keep using the engine that's already in my car until I get the original engine built.


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## freethinker (Nov 14, 2009)

extinctmake said:


> Thanks. I'm not really sure how many miles the engine has. When I got the car it was a disaster. The odometer read just under 50k, but it might have been 150k for all I know. I finally disassembled the short block last year because the pistons were frozen in its bores. It seemed to clean up okay, so I think the engine is rebuildable.
> 
> I would like to get away without boring the block .060. I'll have to see who makes dished pistons for a 389.
> 
> ...


yes they make thicker head gaskets that will lower compression somewhat but if you are going to rebuild it anyhow and buy new pistons why not go that way.


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## extinctmake (Feb 8, 2011)

I agree freethinker, thanks. I'd like to just rebuild it right with the only alteration from stock is a more livable compression. 

Another question I have regards main bearings. I noticed while looking at the Sealed Power parts listing for my engine that grooved upper main bearings were offered. I suspect that is for improved oiling. Is that overkill for a street-use stocker? 

I also expect any dished pistons would be cast and that forged dished pistons do not exist, nor would forged pistons be necessary for the street.


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## freethinker (Nov 14, 2009)

extinctmake said:


> I agree freethinker, thanks. I'd like to just rebuild it right with the only alteration from stock is a more livable compression.
> 
> Another question I have regards main bearings. I noticed while looking at the Sealed Power parts listing for my engine that grooved upper main bearings were offered. I suspect that is for improved oiling. Is that overkill for a street-use stocker?
> 
> I also expect any dished pistons would be cast and that forged dished pistons do not exist, nor would forged pistons be necessary for the street.


groved mains are a good idea in any engine. i think you can get forged pistons in any custom configuration. cost is the only issue. i feel comfortable using a name brand cast if they were available.


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## BearGFR (Aug 25, 2008)

extinctmake said:


> Hi all, this is my first post to this forum. I own a frame-off restored '65 GTO convertible that I completed a little over five years ago while owning the car for over 25 years.
> 
> My car is equipped with the correct WT-code 335-horse 389 with the correct Carter AFB (3895S) and a Muncie 4-speed transmission. Many years ago, as a 19-year-old pimple-faced kid with my then run-down GTO, I bought this engine from a machinist I was acquainted with (now friend who's since retired from doing machine work) who built this engine for his '57 Pontiac street rod. It was the first part I bought for my GTO. The engine has a compression ratio of at least 10:1 and is likely closer to 11:1.
> The engine runs well for a stocker. He re-curved the factory distributor to give full advance at 3,000 rpm. The engine runs the factory grind 067 cam, but it has the poly lock rocker arm nuts and a couple of other tricks like a port-matched intake manifold.


Welcome! Sounds like you've got a really nice car there.

I feel your pain. Not too long ago I built my 69's numbers-matching 400 into a 461 stroker with factory iron heads for a 400. I had to really struggle to get the compression down to where it needed to be.

Couple things. One is you need to pull those heads and CC the chambers to find out where you're really at. It's common for there to be quite a bit of variance from the "factory" numbers, and you really need to know exactly where you are now in order to plan your route to where you want to be.

Two, whoever said an overbore and larger displacement would raise your compression was dead on. That's exactly what it would do. Plus, I'd be really hesitant to bore my original block any more than I had to just for the sake of longevity. There's only one "original block" for any given car.

Another consideration is your budget and how you plan to use the car. I understand you want to keep it pretty much original stock, aren't interested in a lumpy idle, and don't want to lose any low end torque. Don't worry too much about torque. Pontiacs ain't Chevy's  My 461 has a moderate solid roller cam in it that you can most definitely hear, and it only makes about 13" of idle vacuum --- however the torque PEAK occurs at a mere 3100 rpm, and that's 540 ft. lbs. I'm not trying to talk you into a lumpy cam, just be aware that you've got some room to play without endangering your bottom end or your idle quality, if you're so inclined. 

So, let's do some figger'in. I'm going to assume +.030 on your 389 as a starting point. That's a bore size of 4.0925 and a stroke of 3.75, for a swept volume of 49.329 cubic inches or 808.66 cc's per cylinder. Nominal head gasket thickness is around .042, and the smallest gasket bore size I've found so far is 4.160 so that's an additional 0.571 inches / 9.36 cc's of clearance volume. Add to that the "usual" Pontiac deck height of .020 (.263 in / 4.31 cc) and now we're at .591 in / 13.77 cc's. Valve reliefs in the "factory" pistons are usually about 6 cc's (.366 in) bringing us up to 1.2 in / 19.67 cc's. All that's left is the chamber volume. "Factory" specs say these heads have 62 cc chambers (3.782 in). If that's what they really are, then you've got a total clearance volume of 4.982 in / 81.67 cc's. Static compression ratio is (swept volume + clearance volume) / clearance volume, or in this case, 10.901:1. If that's what it really is, then yeah, it's too high for 93 octane. If your chambers are really 66 cc's though, that brings it down to 10.439:1. 70 cc's would make it 10.018:1 - and you could almost get away with that, with the right cam and cam timing.

But, just for the sake of agrument, let's say that your engine right now (or with a 0.030 overbore) really is 10.901:1. To get it down to 9.3:1 (good safe number for 93 octane) you need an additional 16 cc's of clearance volume from "somewhere". You've got three places it can come from: bigger chambers, dished pistons, thicker head gaskets - or some combination thereof. Bigger chambers means a combination of cutting on them and/or sinking the valve seats deeper into the heads. You might be reluctant to do that to your orignal heads - so would I - at least not 16 cc's worth. Thicker head gaskets would do it, you can get Cometic gaskets in pretty much any thickness you want. 0.110 compressed thickness gaskets would put you at 9.352:1 with no other changes. Here's the thing though: doing that would absolutely KILL the quench/squish area between your pistons/heads and do bad things to combustion efficiency due to decreased turbulence in the chamber. It would also expose more "hot cast iron" to combustion temps which could actually make your motor more likely to detonate. My opinion is that this isn't the way to go unless you've got no other choice. That leaves dished pistons. I expect Mr. P-Body will chime in here directly, but if it were me I'd do my best to find a good light forged piston that has a D-shaped dish in it totalling 20-21 cc's in volume, and I'd run .045" compressed thickness gaskets - very close to stock dimensions but still helps a little. The reason the D-shaped dish is important is that it preserves the quench/squish pads in the chambers that produce turbulence, and that's good for both combustion efficiency and detonation prevention.

What I don't know is if such a piston is "out there" anywhere, or if you'd have to have a set custom made. I made a few searches and didn't find really anything, so that might be the kicker.

They can be tough to find. It took a lot of work and research to find the combination that would allow me to run my #722 heads with their 72 cc chambers on my 461 and still stay below 9.5:1, and even after we found them they still needed some addtional machine work to tweak them. Even then I had to make some compromises to "get there".

Figuring all that out though and being successful at it sure was a lot of fun.

Bear

p.s. To make all those calculations, I used a spreadsheet I made back when I was doing all this stuff for my motor. You're welcome to a copy if you want it.


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## extinctmake (Feb 8, 2011)

Wow Bear, thanks a bunch there. Since I already have the engine apart, I should take the heads to a machine shop and find out how many cc's the combustion chambers are on my old #77 heads. 

I don't know if any significant work was done to the engine. When I disassembled it last year, it had a replacement timing chain (nylon cam gear had been replaced) and the rod bearing caps had punch dimples on them to denote which cylinder they belonged. I suspect someone replaced the rod bearings at some point. 

This car was ran really hard, abused, and was a total pile when I got it. 

My guess is the heads and the deck of the block have not been altered from factory, but I must get a confirmation that it's fact.

You've provided a trove of useful information. I've already ruled out the thicker head gasket route and cutting on those heads to increase the chamber volume sounds risky. I also learned that many vintage Pontiac engines had a different compression ratio than what was advertised. 

I really would like to avoid boring the block .060 to fit dished 400 pistons, if that would even reduce my compression in the first place. Based on the replies to my thread, I'm thinking that course of action won't work. Perhaps I can find a skilled machinist in my area who can cut dishes into replacement flat 389 slugs.

I did some online searching of dished 389 pistons and after a few takes, I realized how much easier a GTO with a 400 is to restore than a 64-66 with a 389. It makes me wish my '65 were a '67.......

I really appreciate your reply Bear.


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## Thumpin455 (Feb 17, 2010)

Where do you live? 

You might not have to run dished pistons, and I have an Edelbrock carb sitting here that would work for you. That way you dont have to pay more than $2.75 a gallon. You could enjoy the high compression and plenty of power with smoother operation. A carb would be cheaper than dished pistons.  It works in my 70, why wouldnt it work for your 65?


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## freethinker (Nov 14, 2009)

Thumpin455 said:


> Where do you live?
> 
> You might not have to run dished pistons, and I have an Edelbrock carb sitting here that would work for you. That way you dont have to pay more than $2.75 a gallon. You could enjoy the high compression and plenty of power with smoother operation. A carb would be cheaper than dished pistons.  It works in my 70, why wouldnt it work for your 65?


what kind of carb is it? is it an e85 carb. thats the only way the carb would make a difference. if so that would be an option if he lives where the fuel is available.


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## freethinker (Nov 14, 2009)

extinctmake. i would just call some of the engine builders on this site and see if they know of a source for 389 dished pistons. they should know.
option 2 for me would be have a set of flattops cut. option 3 would be boring to 400 and using dished 400 pistons. 400 pistons are more readily available.


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## Mr. P-Body (Jan 20, 2011)

Bear is right on the money. So is freethinker. There is no carb that will reduce detonation to a tolerable point. While it may not be "heard", it still exists. The ONLY way to ward off detonation FOR SURE, is to lower the static compression ratio. The "laws of physics" will not be denied.

Speed Pro (TRW/Sealed Power) L2111F pistons are still "out there". With some dilligence, a set could be found for your "over bore". They have PLENTY of "meat" in the head of the piston to turn a dish to up to 25 CCS. 

If your budget can "stand" it, BRC makes dished Pontiac pistons in any diameter and pin height for a reasonable price (under $700). Ken Keefer (Pontiac Dude, Brookesville, FL) is the "outlet" for these. You tell THEM what you need. 

We do a fair number of these "restifications" (a true restoration would include the "high" compression). Once the compression has been lowered for using 93 octane, power loss is experienced (compression IS "power"). To compensate for this, we use Comp XE grinds. They have proven to be superior to others in the lower compression engines. For a "sound" and performance similar to the 068 or 744 cams, we use XE262H. For the milder 067, XE256H. Ignore the "buzzing in your ear" from the nay-sayers. These cams, when properly installed and applied as "intended", have no peer. These "low compression" engines actually make more power than their "original" counterparts.

The Lunati "VooDoo" series is very similar to the XE desiign (same original engineer, Harold Brookshire). We've only read about them, and have no specific experience with them. 

I wouldn't "mess" with the heads. Those are getting rare as hen's teeth, and IMO, should be "saved for posterity".

FWIW

Jim


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## Thumpin455 (Feb 17, 2010)

Of course it would be an alcohol carb, E85 is dirt cheap and can be used easily over 13:1. If he doesnt have it available, then its dished pistons. If he does have it available, its not much more than a carb swap. Thats why I asked where he lived, I can find stations that carry E85 for him, as long as I know where to look.

The only way to get around detonation issues with lots of compression is to not use gas. He doesnt drive it much and he can use his current fuel system, but I would use an electric pump with it, mostly because I like them.


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## BearGFR (Aug 25, 2008)

extinctmake said:


> Wow Bear, thanks a bunch there. Since I already have the engine apart, I should take the heads to a machine shop and find out how many cc's the combustion chambers are on my old #77 heads.
> 
> I really would like to avoid boring the block .060 to fit dished 400 pistons, if that would even reduce my compression in the first place. Based on the replies to my thread, I'm thinking that course of action won't work. Perhaps I can find a skilled machinist in my area who can cut dishes into replacement flat 389 slugs.
> 
> ...


You're quite welcome. I bet Jim Lehart (Mr. P Body) will have a source for good 389 pistons if anyone does. 

You can cc those heads yourself, I did mine. All you need is a flat piece of plexiglas large enough to cover the chamber, some grease, and a large medical syringe (like one of those big plastic ones they use for flushing out wounds and stuff). Drill a small hole it the plexiglas so that it's at the "top" edge of the chamber, use a small bit of the grease on the valve seats to seal the valves and also to seal the plexiglas to the face of the head, then use the syringe to measure a liquid (I used blue windshield washer fluid) into the hole until you get the chamber full. While you're doing it, tilt the head so that the hole is highest point to allow air to escape. To make sure you're accurate, measure each chamber 2 or 3 times then average all the measurements to get a good reading on each one. (If the valve springs are still installed, you won't need to bother with sealing the seats with grease - the springs will hold them shut so they don't leak fluid - unless the seats are leaking and need a valve job.)

The reason a little more aggressive cam can help with compression/detonation is this: as the piston starts up on the compression stroke, it "generally" can't start making compression until that intake valve closes and seals off the cylinder. So a cam with a little longer intake duration (and/or installed a little retarded) delays that intake closing event some, resulting in less cylinder pressure because the piston doesn't have as long to squeeze on it. It's really not the best way to manage detonation, but if you've got a motor that's borderline, it can help just enough to keep you safe. I said "generally" above because when the motor's in the fat part of the power band and intake flow velocity is high, the inertia of the incoming air/fuel charge, moving in the opposite direction of the rising piston, lets pressure start to build some even with the valve still open.

Fun stuff to play with and think about

Bear


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## geeteeohguy (Feb 2, 2008)

Extinct, I was reading this thread and hoping some folks would chime in, and they did. My experience has been: a .060 overbore for standard 400 pistons is a possiblility, and it CAN lower compression IF the "cheapy" 8-valve-relief-jobber pistons are used. The compression will be lower because this piston has a lot of valve reliefs, a rounded crown, and sits waaay down in the bore: all terrible for good performance. Plus, a .060 overbore on a block that needs a .030 is a no-no. My personal experience is similar to yours....the 389 in my own '65 was rebuilt be myself 30 years ago, but has only gone 50,000 miles in that time largely because it now requires "race gas". I rebuilt a 389 for a friend for his own '65, and we used expensive, custom dished pistons, and man, does his car run strong. Yes, the custom pistons were expensive, but he's at about 9:1 and the car feels like it runs as hard as mine, and does it on 89 octane, too. I am a fossil when it comes to modern techniques and cam grinds that work in Pontiac engines.....refer to what Bear and Mr. Peabody are saying, and you'll be ok. In fact, when I get around to playing with another combination, that's where I'm going for answers!! Good luck, and have fun.


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## extinctmake (Feb 8, 2011)

I must say I am impressed with all of the responses on this thread. I find comfort in knowing there are plenty of Pontiac gear heads out there. I think I'll try to cc my #77 heads Bear. I need to find some plexiglass. The heads are still assembled. I want to believe they have never been touched. I'll know more once I get them out of my basement.

I live in Nebraska, so E-85 is the state beverage. I have been reading a little about E-85 and how it is a high octane fuel. I also read conflicting reports that E-85 is corrosive and my car will sit over half the year with it's tank fuel along with a chaser of Stabil. I think fuel hoses are affected by E-85. I should research the E-85 topic a little further. 

As for changing carburetors, adding an electric fuel pump, etc. here's where I become a royal pain....I'm a stickler for keeping this rig as original as possible, negative side affects and all. I am well aware that the pieces that Thumpin455 mentions are far superior to the Carter AFB and Delco points distributor my engine has. I just think a numbers-matching, or at least very correct, '65 GTO convertible is a valuable piece and still an enjoyable one. If the 100 octane I had been buying was still in the $4 to $5 per gallon range, I'd be content with the current sky high compression engine I have in my car now. It is as Mr. P-Body describes; a true restoration. And there are some shortcomings by restoring my car in that direction. Believe me, I am envious of the guys who build their cars without any "rules." If I had that sort of wisdom, I'd already have a hot 400 that screams on Kwik Shop 87 octane swill in my GTO.

I think geeteeohguy has the 400 pistons pegged that I heard about from someone at a car show that could be used on a .060 over 389. I saw a photo of them and they have a collage of valve reliefs that look like they could make an engine compression drop very far. I still want my GTO to run like one. I agree with you guys about the pitfall of boring my block .060. You've talked me out of that idea. 

I think where my wriggle room with altering my car lies within the internals. Nobody can see the cam and pistons. I am intriged with the Comp XE cams Mr. P-Body shares information on. Can these camshafts be installed straight up, or will they need to be degreed? I would be thrilled to be able to restore my original engine with all of its numbers-matching castings and parts in tact while running on pump gas just as well (if not better) as my car ran on the old Ethyl gas back in the day.

I plan on looking into finding some .030 over dished 389 pistons or finding a machinist who can cut a dish in a flat top piston. I think the numbers-matching engine to my car warrants some extra expenditure. I want to re-build the first engine to my car to be the last engine to this car. 

I sure am glad I ran into this thread. I'd like to drink some beers with all of you guys.


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## Mr. P-Body (Jan 20, 2011)

The multi-relief 400 pistons are about 12 CCs vs. the 7 in a "normal" (4-relief) piston. We don't recommend them as even though the static compressin is lowered slightly, flame propagation is "hurt", and turbulence in the chamber is high. Not a bad choice for a "raggedy rebuild", but not a very good choice for a performance-oriented engine. 

As said, Speed Pro L2111-xxx is a good one. It has plenty of "meat" for the necessary dish. If you can't find someone "local" to dish them, let me know. I agree, don't go .060" until it's absolutely necessary.

If using a high quality "true roller" timing set (Cloyes, Comp, Melling, etc.), the cams usually "come in" right on the money. If using a lesser set (SA Gear, etc.), it MUST be degreed to be sure. It's never a "bad idea" to degree a cam. Standard procedure here during assembly, regardless of cam OR engine family. It's not THAT complex, either. If you can properly assemble your own engine, you can handle degreeing the cam.

Jim


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## geeteeohguy (Feb 2, 2008)

Extinct, you are doing exactly what I would do. I think you're making the right choice. I've had my '65 Hardtop and '67 Convertible for decades, and they are pretty close to original (the convertible is). The value as an original GTO is much greater than a modified one...a lot of guys on the forum modify for better braking and drivability, and it works very well for them. These are modifications that can easily be reversed if need be without compromising the entegrity of the car. That said, I've been running the original Delco Points distributors and factory carbs and intakes on my cars for the past 30 years without issue. Nothing wrong with Genuine GM Parts!! Also, I'm a bit eccentric in that I want to "experience what it was like in 1965" when I drive my GTO....this means drum brakes, no cup holders, etc. When I drive my GTO, it is just as raw as it was back then. I like that. As I stated, I am in the same boat as you with the high compression on my 389. I may eventually install different heads. It doesn't need a rebuild. I solved the years-old dteonation problems in my '67 by installing 87cc heads on it. Now I can drive the car anywhere on cheap 87 or 89 octane gas. I've put over 120,000 miles on this car since I've owned it, and I drive it on long trips and cross country regularly. Let us know what you plan to do. I think the dished pistons and compatable cam will do the trick. It certainly worked for my friend's 389 that I mentioned in the previous post. All the power of a high HC job, but fun to drive because you don't need $$$$race fuel.


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## BearGFR (Aug 25, 2008)

extinctmake said:


> I think where my wriggle room with altering my car lies within the internals. Nobody can see the cam and pistons.


There ya go. That's exactly the logic I used when I built (with Mr. P's tutelage) my numbers-matching 400 from my GTO into a solid roller 461. The only extermal visual clues that something is up are the headers, and if you look closely, the engine-color-painted valve cover spacers. If you look REALLY closely and know something about Pontiacs you'll notice that YS-code 400's didn't come with casting number #722 heads. But those are the only clues ---- 



 


You don't have to run an electric pump to get adequate fuel delivery. I'm using a mechanical, supplied by RobbMc, that's supposed to be able to feed engines up to 1100 HP. I had InlineTube make me a 1/2" stainless steel fuel line to replace the original 3/8" line and also routes in the same location from the tank to the pump. I did add a rear sump to my fuel tank, though, and I replaced the factory 10-bolt with a Moser 9".

I've "upgraded" other things too, like brakes, suspension, and steering, but for the most part I can pass the car off as "mostly stock' - to the casual observer at least. 

Bear


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## Thumpin455 (Feb 17, 2010)

Living in Nebraska and running 87 octane? Why? If I still lived there nothing I own would be running gasoline and all of them would have as much compression as I could get. 

It doesnt make much sense to dish the pistons when you have race fuel at the pump for less than $2.50 a gallon. Particularly so when the only big change you need to make is to the carb.


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## BearGFR (Aug 25, 2008)

extinctmake said:


> I live in Nebraska, so E-85 is the state beverage. I have been reading a little about E-85 and how it is a high octane fuel. I also read conflicting reports that E-85 is corrosive and my car will sit over half the year with it's tank fuel along with a chaser of Stabil. I think fuel hoses are affected by E-85. I should research the E-85 topic a little further.


I know very little about E-85 other than what you've already said, it's high-octane and is hard on fuel system components. I seem to remember hearing that it was particularly tough on rubber, attacking things like fuel hose, carb needle valve tips, pump diaphragms, rubberized cork gaskets, etc. -- but don't take anything I say over your own "hard" research.

Bear


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## freethinker (Nov 14, 2009)

BearGFR said:


> I know very little about E-85 other than what you've already said, it's high-octane and is hard on fuel system components. I seem to remember hearing that it was particularly tough on rubber, attacking things like fuel hose, carb needle valve tips, pump diaphragms, rubberized cork gaskets, etc. -- but don't take anything I say over your own "hard" research.
> 
> Bear


thats a myth. i ran straight ethanol in a circle track race car for years and never saw any corrosion of anything.


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## geeteeohguy (Feb 2, 2008)

Alcohol absorbs water and is soluable in water. A friend ran his GTO on alcohol when in trade school years ago, and had some rust issues, but that was after the car "sat around". This was in arrid Arizona, though. He had no rubber issues that I'm aware of. He said the car made a ton of power but used twice the fuel at least. He ran an extensively re-jetted carb. I think if you used the car often, and didn't let it sit, you'd be ok. Alky GTO runs his on E85, apparently without issue. If I lived where E85 was available, I'd do the research and give it a try.


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## freethinker (Nov 14, 2009)

geeteeohguy said:


> Alcohol absorbs water and is soluable in water. A friend ran his GTO on alcohol when in trade school years ago, and had some rust issues, but that was after the car "sat around". This was in arrid Arizona, though. He had no rubber issues that I'm aware of. He said the car made a ton of power but used twice the fuel at least. He ran an extensively re-jetted carb. I think if you used the car often, and didn't let it sit, you'd be ok. Alky GTO runs his on E85, apparently without issue. If I lived where E85 was available, I'd do the research and give it a try.


the only problem i had with ethanol is that if you have a car that sits a lot you have to drain it. ethanol when it evaporates turns to gum. if you have a carburated engine and it sits long enough for the fuel to evaporate out of the fuel bowl it leaves a gummy mess behind. simple solution is to drive it more often.


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## extinctmake (Feb 8, 2011)

You've got one mean machine Bear. I like how you kept the Quadra-jet carb on . As for E-85, there's plenty to be had in the Omaha/Bellevue, Nebraska area where I live. I do have a car that sits much of the year, so the gumming issue freethinker mentions would be a problem.

I have to admit Thumpin455 has piqued my curiousity as to how well the little monster in my car now would run on E-85. Maybe there's some guys at the weekly cruise-in spots in toen that run E-85 who could provide some insight about how it works for them in my area. It's not arrid here like Arizona. It gets pretty humid here in the summer. 

As for the forged Sealed Power pistons Mr. P-Body mentioned, NAPA offers them for about $62 each, so I could get a set and have them dished. I need to find a local machinist who knows something about Tin Indian Eights.

I'll be talking to you all really soon.


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## Thumpin455 (Feb 17, 2010)

Charlie at C&L Machine in York.. I think thats the name he uses.


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## BearGFR (Aug 25, 2008)

While you're thinkin', here's one more tidbit of information to throw into the mix. Everything else staying the same, a full 5 points of compression (the difference between 9.5:1 and 10.0:1) is only worth about 6 to 8 horsepower in a motor like my 461. That makes it not worth pushing the envelope and trying to live "on the edge", in my opinion at least.

Bear


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## Thumpin455 (Feb 17, 2010)

I havent had any gum issues with it evaporating, nor with it soaking up water. It does get humid here since I live about a mile from the worlds largest fresh water lake. The GTO sits all year, last year it only moved around enough for me to paint it. Doesnt seem like it is going bad in the tank or anything else. Ethanol isnt anything mysterious, its the same stuff that is in a bottle of jack or jim. If it was highly corrosive would there be aluminum cans and lids holding it for human consumption?

Anyway, its an option to run high compression with cheap fuel with out much effort nor expense.


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## geeteeohguy (Feb 2, 2008)

Thumpin, I think we all know alcohol itself is not corrosive to metal, rather its the ability it has to absorb and hold moisure. It's like brake fluid that way....it absorbs moisture out of the atmosphere. But I think if anybody would know about its feasability, it would be yourself or AlkyGTO, since you have both run the stuff for a long time without issue. Alcohol does not "go bad", either. Just ask any 12 year old bottle of Scotch!!! A lot of us out here (ME) have ZERO real world experience about running it as a fuel, and are curious.


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## Thumpin455 (Feb 17, 2010)

It bonds to water, its kinda cool how it does it. The way it works it will not separate, and you only have problems with water when you get more than 20% of it in the fuel. The gasoline will separate out of it long before you reach that much. It would be hard for a ten gallon tank of fuel to absorb 2 gallons of water unless you dump it in.

I have a flat top Ross slug crank kit on its way from Tennessee, when it gets here its going in a 455 block with ported 670 heads, should be around 11.5:1. Then its going in a 79 TA when the snow is gone. If the 48 heads get back from Butler before the snow is gone, it will get those for right at 13:1. If you guys want to know about it, I will start a thread. The 455 in the 70 GTO is going to get those 670 heads when the 48s are done. I am more than willing to share the hows, whys, whats, and everything else.


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## BearGFR (Aug 25, 2008)

Thumpin455 said:


> It bonds to water, its kinda cool how it does it. The way it works it will not separate, and you only have problems with water when you get more than 20% of it in the fuel. The gasoline will separate out of it long before you reach that much. It would be hard for a ten gallon tank of fuel to absorb 2 gallons of water unless you dump it in.
> 
> I have a flat top Ross slug crank kit on its way from Tennessee, when it gets here its going in a 455 block with ported 670 heads, should be around 11.5:1. Then its going in a 79 TA when the snow is gone. If the 48 heads get back from Butler before the snow is gone, it will get those for right at 13:1. If you guys want to know about it, I will start a thread. The 455 in the 70 GTO is going to get those 670 heads when the 48s are done. I am more than willing to share the hows, whys, whats, and everything else.


That'd be great. I've been curious about "real life" long term experiences with E-85.

Bear


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## extinctmake (Feb 8, 2011)

Hey Thumpin455, what about mixing E-85 with premium unleaded? Let's say E-85 has 103octane straight from the pump. If premium unleaded gas was blended with E-85 would it correct any of the side effects of ethanol we've discussed on this thread?

Would somebody like me be able to use a 50-50 mix of preminum unleaded and E-85 without having to make any modifications and achieve a decent octane level? 

Maybe the octane level would still be high enough to prevent detonation in an engine with 10:1 to 11:1 compression.


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## Thumpin455 (Feb 17, 2010)

I have not had the problems most people cite, and quite often they are confusing methanol with ethanol. It isnt very difficult to run E85, and since 07 I havent found any problems with the stock fuel system on the 70. For the most part if the system can handle 10% ethanol, it can handle 70%-100%.

That would be like making it a flex fuel vehicle. Getting it to not run too rich or too lean with a mix would be the problem. There is enough difference in jetting for gas and ethanol that mixing it with a carb makes it difficult to get the mix right. The range from winter to summer blends isnt usually enough to cause problems unless you are running it ragged edge lean for max power. But knowing how much of each fuel is in the tank would be a problem. 50-50 would require its own tune, and Im not sure how much you would need to open it up.

Also mixing premium isnt really needed. Ethanol raises the octane enough you can run 87 or lower with it with more than 40%. When they mix E85 they use the lowest octane gasoline they have because it raises it so much. It acts like more than 105, and it really is. The test for octane isnt very good at measuring ethanol.

I've mixed 87 and E85 in my 98 Formula, it has the LS1 which requires 91-93, the mileage is about the same on E40 if I can stay out of the throttle. The Formula is lucky to get 24mpg on straight 87 octane, it backs the timing way down and kills the power, thus needing more fuel. If I run more than 40% the ECM doesnt like it and throws a lean bank code, then starts dumping fuel. The injectors need to be a bit bigger and the program needs some tweaking to run E85.


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## 66tempestGT (Nov 28, 2009)

:agree im pretty sure ALKYGTO is running methanol on the blower car not ethanol.


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## extinctmake (Feb 8, 2011)

Okay, this kind of goes against my criteria of wanting to keep my GTO engine all original, but an opportunity for a set of 6X heads would enable my 389 to operate on a lower compression ratio.

Now I've read in the past that using 1971 and up heads on an older high compression engine will lower the compression ratio. 

My question is whether a set of 6X or 1971 400 heads is a direct bolt-on. In other words, could I rebuild my 389 using the flat top replacement pistons and then bolt on a set of "smog" 400 heads without any modification? Should I assume this would lower my compression ration down to the 8.5 to 9-to-1 range?


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## geeteeohguy (Feb 2, 2008)

extinct, don't assume anything when going thru the expense of building an engine. For a compression of 9 or 9.5 to 1, you want heads with about an 82-87cc chamber. Only two head castings I'm aware of are at about 87cc, and both are 1970 units: the #64 455 heads (HO GTO) and the smaller valve 1970 #15 heads (455). I'm running a pair of re-worked #15 head on my '67 400 and they work well on pump gas with flat top pistons. The #64's are rare and run $$$$$. Bigger cc heads can be had on the cheap, and milled to achieve a 90cc or slightly less chamber. Others will help you out here. Also, and this is important: the valve reliefs on a 389 piston are at a different location than the 400 pistons. This means that post '66 heads have valves at a different angle, and they may hit your 389 style pistons. Some have gotten away with it, but the issue comes with higher lift camshafts. Mr P Body can enlighten you on this better than I. In theory, you should be able to run late model heads on your 389 provided you stick to a reasonable camshaft. But, you do need to be aware that there cold be interference issues. You can check clearances as you assemble the engine using modeling clay, etc. Others will hopefully add their 2 cents.


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## extinctmake (Feb 8, 2011)

Thanks again geeteeohguy. It sounds as if my best bet is to find a machine shop competent enough to dish my 389 pistons and just run my #77 heads.

To tell you the truth, I'm starting to get a little discouraged about trying to build a decent engine that will run on today's gas. If I had a 400 or 455, it would not be a problem. I guess a 389 is a little more challenging.

As little as I drive my car the way it is, I could buy a lot of 100 octane fuel for the cost of building my other 389 to run on unleaded. However, maybe I'd get out and enjoy my GTO more if it ran on run-of-the-mill unleaded.

I really appreciate the unput everybody has given me on this thread. At least I have options and at least my car does run even if I do nothing.


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## BearGFR (Aug 25, 2008)

extinctmake said:


> To tell you the truth, I'm starting to get a little discouraged about trying to build a decent engine that will run on today's gas. If I had a 400 or 455, it would not be a problem. I guess a 389 is a little more challenging.


Buck up there, Buckaroo... :seeya: If it was easy, we'd all be working on ::cough:: ::spit:: "Chevy's".  The "Chinese menu" of the automotive world --- "choose a block from column A, heads from column B, cam from column C..." build a motor that's just like 10-gazillion others out there, be sure and check your brain at the door because you won't need it - it's all "been done before".

Pontiacs are for people who still believe in creativity, doing things their way, bucking the trend :cool, and making bottom end torque that the "bowtie brigade" can only fantasize about...

Bear


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## extinctmake (Feb 8, 2011)

Thanks Bear. I think I'm stuck 20-25 years back when I first bought the engine that's in my car. There's fewer Pontiacs out there and fewer good machine shops that know more than just how to work on a Chevrolet.

I wish the good gas was more available and not $7.99 a gallon. I'd love to rebuild my numbers matching WT 335-horse, GTO 389 the way DeLorean intended. 

I think based on the sound advice I've received from guys like you, I will try and find a machine shop that can alter a set of Sealed Power 389 forged pistons to reduce my compression enough to run on today's fuel. I will run my #77 heads. 

I plan on looking at the different cams Mr. P-Body suggested earlier in the thread. Maybe selecting a cam that functions better with a lower compression ratio will help make my 389 run the way DeLorean intended, but on 87-91 octane swill.

In the meantime, I will patronize the gas station that sells the 100 octane juice and I will fill my tank to properly feed the high compression snot-monster that's in my GTO now.

I can't wait until spring guys. I wish I could cross paths with you all at a cruise spot.


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## geeteeohguy (Feb 2, 2008)

extinct, no worries. As I said, I helped a friend with a 389 that went into his 4 speed 3.23 geared '65. It was a 66 big car 389, with worse heads than the 77's. It had the 092 heads. All we did was install the dished pistons and a Comp XE268 cam, and that thing screams. It feels like it runs as strong as my high compression 389 (same basic car as his) and it does it on 87-89 octane. He's put over 5000 miles on it running cheap gas, and he's delighted. The price of the pistons are long forgotten, and he's not wincing every time he fills up like I am. You'd be surprised how well a 9:1 389 will run with the right cam and dished pistons. Doing another 389 for another 4 speed 3.23 GTO this spring and am doing the same thing. From my research, and what others say, an XE262H cam is an excellent choice in these engines. My buddy picked a 268, which is slightly more "hi perf", and as I said, his car flat screams.


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## Mr. P-Body (Jan 20, 2011)

We've built MANY 389s that are mUCH stronger than opriginal engines, using 93. Some on 89. The XE cams make HUGE difference between 2,000 and 6,000. 

We've learned out of necessity, "flow trumps compression". That is, an engine with superior flow will smoke one with higher compression. This goes against "old school" convention. 

We have one '66 GTO out there with the original 389, pistons dished to 9:1, XE262H and the TriPower. Traction is impossible in 1st gear... It pulls hard to just over 5,600. 

The "future" is here. Relax and trust us. 

Jim


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## BearGFR (Aug 25, 2008)

Mr. P-Body said:


> We've learned out of necessity, "flow trumps compression". That is, an engine with superior flow will smoke one with higher compression.


:agree Oh yeah.. :cheers Engines after all are just big ol' air pumps. The power they make comes from the fuel they burn, the more fuel you can burn _efficiently_ on each stroke, the more power you get - and burning efficiently requires oxygen from the air, so the more air flow you can get......

That's the bottom line function that's common to "the big 3": superchargers, turbos, and nitrous - getting more oxygen into the cylinder so you can efficiently burn more fuel to release more energy.

If you're going "au natural", then "more air" has to come from head flow, intake manifold, cam profile, port size, air column velocity, carb flow capacity, effective valve opening area, combustion chamber characteristics, exhaust efficiency... all that fun stuff. 

Bear


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## freethinker (Nov 14, 2009)

yes but in two engines with equal flow the one with higher compression will make more power with racing fuel. the nascar boys used to build compresson up to 14 to 1 until the rules mandated 12 to 1 max.

it has to do with running compression vs static compression and ve.


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## Mr. P-Body (Jan 20, 2011)

The whole point is to NOT "need" racing fuel. A race car is one thing. A street car is an entirely different animal... Low speed power, drivability, practical fuel, etc.

Jim


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## extinctmake (Feb 8, 2011)

Thanks guys. I value and trust your advice. I think the first move I need to make is finding the pistons or a machine shop that can dish some 389 pistons.

Spring has sprung and I plan on getting out with my GTO and find out where/who I need to handle the machine shop chores for my engine.

I am inspired to check out using a XE-brand cam. If I'm going to spend some bucks to build an engine, I might as well make it look OEM while making it run better than factory on today's gas the way you guys state it can.

This will be a fun project.


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## Thumpin455 (Feb 17, 2010)

I have a set of 6x heads on a 400 out in York. Pm a phone number and I will have my bud yank em next time he gets up from Geneva. If you want to run crap gas, hey, no problem. I dont need the smog heads anymore.


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## Mr. P-Body (Jan 20, 2011)

If you can't find a local shop to set up your pistons, gimme a call. 

I currently have a set of .030" over 389 pistons. They're Nylen/Ohio castings. Not suited for serious performance, they'd be fine in a streeter that isn't "serious" about high-end power. 

Speed Pro L2111s are still "out there", but oversizes can be "spotty". Pontiac Dude (Ken Keefer) offers a good price on "customs" from BRC, with any bore size, pin height and head "configuration" (dish, bump, etc.). Forgings are better suited to performance applications.

Jim


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## extinctmake (Feb 8, 2011)

Thanks Mr. P-body. I might take you up on your offer to buy your pistons because I'm not confident I will find a machine shop in the Omaha area that will have a clue of dishing a set of 389 pistons. Maybe it doesn't matter what make of engine the pistons are for and a good machine shop can dish the pistons for any engine. I'll have to find out. I think I can buy Sealed Power (part number SEP L2111F) pistons at the local NAPA parts store for about $62 each. 

Another reason I'm back on the thread is all of you got me thinking on cam selection. Maybe I'm stuck in the old low lift, long duration patterns that Pontiac ran 40-odd years ago. I am confused about the profiles of many of the cams you recommend for street use. I looked up the specifications of some of the COMP cams grinds and I noticed some huge differences.

The standard four-barrel 1965 GTO cam has an intake lift of .406-in, exhaust at .408-in and duration of 273 degrees intake and 289 degrees exhaust with 54 degrees of overlap. When I initiated my plans to rebuild my original engine, I assumed it would be best to use a similar grind cam. The Sealed Power cam I looked at differs just slightly with the Pontiac cam.

Then I looked at the numbers for a couple of the Xtreme Energy cams discussed on this thread. The tale of the tape between these and the factory cam is a mismatch:

XE256H: Hydraulic-Strong torque through low end and mid-range, good idle. Lift .447 intake and .455 exhaust with a duration of 256 degrees intake and 268 degrees exhaust.

XE262H: Hydraulic-Excellent response, good mileage, Stock converter mild gear. Lift .462 intake, .470 exhaust with 262 degrees intake duration and 270 degrees exhaust.

XE268H: Hydraulic-Good for Street Machines, slightly rough idle. Lift .477 intake .480 exhaust with 268 degrees intake duration and 280 degrees exhaust.

One more I thought would be more streetable, due to the following advertising pitch:
XE250H: Hydraulic-Very strong torque excellent mileage, smooth idle. This one has .432 lift intake and .444 exhaust with 250 degrees intake durations and 260 exhaust. This is still a stout piece compared to the "067" style cam I have.

Will I still have a smooth if not decent idle running any of these cams? Is it because I'm lowering my compression that necessitates a much higher lift and lower duration that these new era cams offer?


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## BearGFR (Aug 25, 2008)

extinctmake said:


> One more I thought would be more streetable, due to the following advertising pitch:
> 
> ...
> 
> ...


Two things: 
1) Select your cam by "the numbers", not by ANY of the advertising verbiage with regard to "streetable, idle, compression, etc." Fact is, every engine is different and there's just too much that goes into the mix (compression, displacement, heads, chambers, flow through the entire intake/exhaust system, etc.) for any of those subjective evaluations to be "right" in all cases.

2) Every cam, regardless of factory or after-market, is going to be a compromise --- it's the nature of the beast with fixed valve timing engines like these are. The compromise comes from the fact that a cam can only optimize the engine's volumetric efficiency (where it makes the most torque) for a relatively narrow RPM range. Below that, the cam is going to be "too big" and above that it's going to be "too small". There's no easy way around that. For max horsepower, you want that "sweet spot" to be high up in the rpm range - because horsepower is calculated: HP = (torque * RPM)/5252.
But, the higher in the rpm range the sweet spot is, the "uglier" the motor's going to be at idle. That lope we all associate with "a hot motor" is really a motor that's falling all over itself just barely able to keep itself running because it's so inefficient at that rpm. A motor that has a nice smooth idle is going to be running out of breath at high rpm because the valves aren't open long enough/wide enough for it to be able to fill its lungs. 

No matter how you slice it, you have to deal with the reality that those intake and exhaust valves opening and closing all the time, and the resulting attempt to be constantly starting and then stopping the flow of intake mixture and exhaust gasses through the motor makes cam design a nightmare. What has changed over the years is that improvments in the ability to measure what's happening in a running engine and also computer simulations have made it possible for today's cam designers to pay attention to how things like ramp opening and closing rates, lobe shapes, lobe separation angles, and to understand how changing these things affects how a motor behaves --- whereas "back in the day" the factory engineers could only guess at them. That's why modern cams are "better".

Still though, thing one is for you to pick what you care about because you really can't have it both ways. It's like a dial with a pointer on it. On one end is a nice smooth idle and good street manners, and on the other end is maximum attainable power for your engine/heads. The more you go in either direction, the other end of the scale is going to suffer. Dat's just de way it gonna be... So --- where do you want to set the dial on your car?

Once you choose that, then I know of no one more qualified than Mr. P Body to help you pick the cam that will put you there.


Bear


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## extinctmake (Feb 8, 2011)

Once again Bear you are a pearl of wisdom. Well, this is how I look at it. I plan on running the small Carter AFB my GTO was born with along with the factory intake manifold and exhaust manifolds. I have a points distributor that has been re-curved. I have a wide-ratio Muncie 4-speed and I run 3.23 gears.

Will my car perform well below 5,000 rpm with one of those Xtreme cams? If I have a 9:1 389 like geeteeohguy is talking about I will have a screamer. P-body appears to be an authority. If I lived in his neighborhood, I'd probably find myself at his doorstep with my WT-code 389 block, #77 heads, my Armasteel crank, rods, etc. and hire him to build me an engine.

I guess what I need to have is an engine that has a smooth idle similar to that of my current WT-code 389. I like the low end torque Pontiacs are known for. My engine will look stock, but will run on the same gas my 2002 Silverado uses. It will be driven around 500-1,000 miles a year. I won't be racing it on any track or any street. I do heat it up a little because it is a GTO and not a Tempest. 

Now I have to admit, the prospect of having an engine that looks the part, but runs much better appeals to me. What a sleeper my car would be to pop the hood and see what looks like a correct '65 GTO 389, but has the Xtreme cam, dolled-up heads, modified pistons, etc., and it runs better than it did in '65 on pump gas. 


In a few years my car will take on a different purpose. My four-year-old son today will have gotten past the booster seat requirement and will be able to join me for a cruise and trip to the show. I will drive the car more as a result. It would be great if I had something that was snotty and still ran on the pump gas. I would be willing to give up some of idle quality for the power gains we've discussed on this thread.

I guess I'm answering the question you posed Bear. You made the perfect starting point with my engine project.


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## extinctmake (Feb 8, 2011)

One more point I should have made earlier. I am willing to change rear end gears. I don't have to run 3.23 gears. Would 3.55s change the game?


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## BearGFR (Aug 25, 2008)

extinctmake said:


> One more point I should have made earlier. I am willing to change rear end gears. I don't have to run 3.23 gears. Would 3.55s change the game?


Sure they would - the hard part is guessing by how much.  

Let me recommend to you a couple of computer programs. There's a company out there, Performance Trends (you'll find them if you Google that), that has some pretty decent engine modeling and drag race modeling software. I used them both extensively when I was deciding how to go with my build --- it was a plus because Jim Lehart of CVMS fame uses the same software, so we could change things and compare notes (and he could validate what I was thinking about).

I got the "plus" version of Engine Analyzer and the base version of Drag Race Analyzer. The advantage is being able to "play with" different engine ideas to see what effect it might have, then you can "transfer" the engine profile into the Drag Race program to get a prediction on how the car might react.

You have to be able to "know" or "measure" quite a bit of information about your engine - the better you are at that the more accurate the predictions will be. The software isn't exactly cheap, but then neither is trying to build an engine by trial and error.

Bear


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## geeteeohguy (Feb 2, 2008)

As usual, Bear's advice is perfectly put and very objective. My experience with early GTO's is pretty fair, and I've owned and driven all flavors of '65 thru '67 GTO's over the years. I vote that you keep the gears you have and run a P-Body recommended cam, probably an XE-262H or the XE 256H (I think...the one that's one step milder than the 262). The 389 will make plenty of usable power, you will be impressed. As I said, my friend with the 268H cam and 9.1 heads has a screamer on his hands, and he'd running a four barrel and iron manifolds. I'm running high compression, radical cam, tripower, and tubing headers. Same gears and trannies on both cars. His idle is noticable, but not obnoxious. You're doing the right thing by researching this to the Nth degree. Getting educated is fun, interesting, and, best of all, will save you MONEY!!! Good luck on your build. AS a PS, I've owned several 3.55 geared GTO's, and even when the speed limit was 55mph, they were terrible on the highway. At $4 per gallon, something to think about.....


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## 66tempestGT (Nov 28, 2009)

i dont know much about cams but i do know that when it comes to technology 40 year old science rarely beats current stuff. i do know i hate paying for racing gas. even my racecar has flat top pistons.


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## extinctmake (Feb 8, 2011)

I would prefer to keep my 3.23 gears because I think my car would be more user friendly on the highway. I just wondered if using a XE256 or XE 262 cam would be counter productive with the 3.23 gears.

Learning about others who have already made the move I'm contemplating makes it much easier, as in geeteeohguy's friend who has succeeded at making his old 389 run great on today's fuel.

I'm also fortunate in that I can take my time finding a machine shop and gathering the right parts to build this engine while running the engine that's already in my car.


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