# Seriously ONE MORE ENGINE COMBO quesion???



## Pontiacpurebrred (Jun 22, 2011)

So I have the 1971 455 block with #98 heads, the 1979 400 block with #6X-4 heads and I just came across a set of #16 heads. 

The 6X-4's on the 455 would work as was discussed earlier, but I may want to sell them with the 79 400 to a T/A guy that is restoring his 79 WS-6 package. I'd hate to break up a rare combo. 

So anyway, the #16 heads are indeed 1968 GTO 400 HO heads 2.11/1.77 with  72cc combustion chambers (IF) I did nothing to modify this combo what would the CR be for the 455 with the #16 heads? 

AND would I be better off with this combo (and dished pistons if need be) than just going with the 6X-4's (ported, polished) with flat top pistons?

I know I am forever changing my mind.


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## BearGFR (Aug 25, 2008)

Man have I ever been there before.... 

Those 16's on a standard 455 with all "nominal" dimensions and flat tops is going to come in right at 11.2:1

Save the file attached to this post on your computer, then rename the file to CompressionRatio.XLS (I uploaded it as a text document but it's really an Excel spreadsheet).

You can use it to play around with measurements and see what effect they have on static compression ratio.

To use those heads, you'll wind up stuggling to find pistons that have enough dish in them and probably will still wind up having more cut into them. You'll be able to get them up to 22 or so cc's, if you're lucky. That still won'd be enough though, so you'll wind up running thicker head gaskets - .075 compressed or more - to get enough clearance volume into the cylinders to get compression down around 9.5:1 or less. Of course doing all that, usiing round instead of D-shaped dishes plus the fat gaskets, is going to murder the quench characteristics of your chambers so it's going to cost you at least some combustion efficiency and also make it a little harder to keep the motor from detonating. Since you'll be down on combustion efficiency you'll probably have to run a little more ignition timing, but of course that's going to make it want to detonate more too.

Oh, and those heads don't have hardened valve seats either so if you "beat on " the motor a lot and load it heavy, you could find it hammering the exhaust seats into the heads on unleaded fuel.

So.... I probably wouldn't recommend it unless there was some overriding reason that you *really* have a passion for wanting to run those heads 

Bear


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## Pontiacpurebrred (Jun 22, 2011)

BearGFR said:


> Man have I ever been there before....
> 
> Those 16's on a standard 455 with all "nominal" dimensions and flat tops is going to come in right at 11.2:1
> 
> ...


As always Bear you ARE my HERO. :cheers

Yea I was wondering more on the E-85 side, I had a feeling I would not be able to get the compression down enough to run pump gas. At 11.2:1 what kind of performance could I expect from the E-85 route?

I would assume it would be a potential screemer with that many cubes and that much compression. IF I ran the right gas. With the proper intake, exhaust, timing and carburation of course. 

Anyway thanks again. 

Scott


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## BearGFR (Aug 25, 2008)

Well, I guess now I can tell you why I "know so much" about that combination.  That's almost *exactly* what I did on my 461. Switch out the #16 heads with their 72cc chambers for a set of #722 Ram Air IV heads with their 72 cc chambers, and you've got the motor that's sitting in my GTO right now. --- and I had to do ALL that to get compression down to 9.46:1 --- and I did give up the quench --- all because I *did* have an overriding passion for wanting to run Ram Air IV heads 

The motor makes pretty decent power, but since it's not really "on the road" yet I don't know if I actually did the right thing or not. Keeping my fingers crossed 

Bear


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## Pontiacpurebrred (Jun 22, 2011)

I have no "overriding passion" to run anything that does not make sense. That said, I am old school enough to be tied to old conventions that "TRUE" HP comes from cubes and compression, I know there's proof to the contrary now-a-days but it's hard to break old habits. 

So with a 455 in my pocket, I have dreams of a 10 3/4: 1 compression beast that I know is probably unrealistic. (without converting a carb to run E-85 that is) SO 11+:1 sounds sexy to me, but I know I am an idiot for that. 

I like the sound of yours and interested to see how it ends up working in practice not just planning.


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## Thumpin455 (Feb 17, 2010)

Well, I had a 455 with forged pistons and an otherwise stock bottom end, with a ported set of 670 heads. The 670 chamber isnt as efficient as the open chambers like the 16, 48, 12, 13, 62, 64, heads have. Still it makes power. With a very mild cam that still pulled 15 inches of vacuum, and a stock converter in a 3700lb Firebird, that 455 ran in the 11s easily. I had to run 4.11 gears in it to keep it from needing a roll bar, the way that worked was it was done pulling before 1000ft. It ran faster with 3.42 gears and picked up almost half a second. 500hp with the small chamber heads is very easy to achieve. 

Back before 2004 E85 wasnt as available as it is now, so I had to run it on race gas. I am using those heads on a 455 with forged rods and pistons now and running it on E85. Mind you, the only E85 pump in the area is 31 miles away from me, there might be a reason why I want to run the stuff. 

One cool thing about ethanol is it has its own oxygen, and one way to make more power is to get more oxygen into the engine. The oxygen content is the real reason you need more fuel than gasoline (not BTU content), and the benefit is more power. The O2 content provides you with more torque from idle to about 4000 rpm, above that the power is usually pretty close to gas, but often still above. The best part of the power comes in at an RPM where the 455 is a beast and its right where you want it in a street car. The only drawback is needing sticky tires to get away from stoplights.

Since you live in Kansas, E85 is everywhere you will be driving. If you want to build a compression engine, then its a simple matter of running flat tops and those heads on a 455. No need for dishes, domes, or anything exotic, just build it, convert the carb, and drive it. Not being handicapped by low octane gas opens up plenty of opportunity. Another added benefit is with the compression you will pick up mileage, how much I have yet to find out, and of course it does depend on driving style as well. If you are into it all the time, it will burn more fuel.

Im not entirely sure why so many people are against compression when there is a fuel available that is cheaper than 87 octane that makes more power and your engine lasts longer when running it. Other than you cant run 87-93 octane in a 400 or 455 with flat top pistons and 72cc heads, there is no drawback to building an E85 specific engine. If you are anything like me, once you run the stuff in a powerful engine, you will be hooked.


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## BearGFR (Aug 25, 2008)

Thumpin455 said:


> Im not entirely sure why so many people are against compression when there is a fuel available that is cheaper than 87 octane that makes more power and your engine lasts longer when running it...


Well in my case, it's just "different" from what I "know" (dang that makes me sound "old") and I'm also nervous about being able to find fuel "everywhere". You make an awful compelling case though. If I could somehow know for sure I could get it to work right and could also easily find fuel, I'd be all over it. The notion of having the motor I have now, but with the added benefits of compression and actual, functional quench in the chambers is very appealing 

Bear


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## Pontiacpurebrred (Jun 22, 2011)

I wish I could get a straight answer out of the guy I am buying this 455 from. I have the date code (a281 - Jan. 28th 1971) but that's all. I just want the letter code (which he can't seem to find) so I can figure out which engine it is. Then I'd KNOW what heads it has. Or should have. Heck I don't even know if it's a 4bbl or 2bbl, I have been assuming it's a 2 but I saw that the 1971 Safari wagon came with both the 2 and 4bbl option on the 455. Big difference HP wise, 280 to 325. :confused


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## Instg8ter (Sep 28, 2010)

Does not really matter what the "Block" was originally, they are all basically the same casting within the same size groups except for the pre 65's and the post 75' 400's, and of course some of the HO and RA variations but even those blocks where for the most part STOCK blocks, heads cam and carb are where they got their HP. Since your going to build it, unless your looking for an engine that matches your build date or something, get the best deal on a virgin short block and have your machine shop check it for cracks, bore .030 over, align hone it and match a good set of heads, cam and carb to it and you can make between 400 and 600 HP even with a lowly 250 hp 73' 455 block on mainly stock parts depending on how deep your pockets are.


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## Thumpin455 (Feb 17, 2010)

Any 455 is a good 455 provided it isnt cracked or broken somewhere. The 2 bolt blocks are more than strong enough for most builds under 600hp and they will take more than 600.

I've only had one engine that needed an align hone it never had the oil changed and I got it with 80k on it. Yes it had sludge. It was a 71 400 from a Gran Prix its not one of the spare engines for the toys. Basically if it needs it do it if it doesnt then dont do it.


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## Pontiacpurebrred (Jun 22, 2011)

Instg8ter said:


> Does not really matter what the "Block" was originally, they are all basically the same casting within the same size groups except for the pre 65's and the post 75' 400's, and of course some of the HO and RA variations but even those blocks where for the most part STOCK blocks, heads cam and carb are where they got their HP. Since your going to build it, unless your looking for an engine that matches your build date or something, get the best deal on a virgin short block and have your machine shop check it for cracks, bore .030 over, align hone it and match a good set of heads, cam and carb to it and you can make between 400 and 600 HP even with a lowly 250 hp 73' 455 block on mainly stock parts depending on how deep your pockets are.





Thumpin455 said:


> Any 455 is a good 455 provided it isnt cracked or broken somewhere. The 2 bolt blocks are more than strong enough for most builds under 600hp and they will take more than 600.
> 
> I've only had one engine that needed an align hone it never had the oil changed and I got it with 80k on it. Yes it had sludge. It was a 71 400 from a Gran Prix its not one of the spare engines for the toys. Basically if it needs it do it if it doesnt then dont do it.


Oh yea, let me be clear, I AM BUYING THIS 455. Which one it is won't stop that or change the build. BUT I am an engine geek, I want to know what it is where it came from and what it was meant to be. (Plus it would be nice to know if it's a 2bbl or 4bbl) ... But yea I am buying it either way. 

I know it don't matter if it's a GTO or Firebird HO 455 or a lowly Safari wagon 455 (obviously since this is the latter) but I'd like to know what it came from the factory as. I was under the mistaken assumption a wagon would ONLY have a 2bbl... I was wrong. So now I want to know. Either way I will know Saturday.  That's the good news. 

I also found out Safari wagons had a 400 option, so now I just want to confirm it's 455. That's the bad news. 

Dude seems to be clueless. (probably why I got it so cheap) OR he is being purposefully evasive. (I hope not)


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## Instg8ter (Sep 28, 2010)

Jim Hand has a 455 safari wagon that he drives to and from the track and runs 11's in. you could order them set up like a GTO if you wanted, his has factory installed endura front end..

Jim Hand


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## likethat (Oct 5, 2007)

There is a 72 gto front end Lemans wagon on ebay right now. I was just looking at it lol. It has a 455 swap in it.


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## Pontiacpurebrred (Jun 22, 2011)

likethat said:


> There is a 72 gto front end Lemans wagon on ebay right now. I was just looking at it lol. It has a 455 swap in it.


That wagon is pretty bad @$$ I would love to have it, dress it up like a GTO, buckets, 4 on the floor, and call it PUFF THE TRAGIC WAGON!!
:rofl::lol::rofl:


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