# Your typical cam question



## Thered72 (Jul 30, 2020)

Hello everybody,

Im brand new to the forum and excited to get to be here. I recently just bought my first GTO ( been saving since I was 13). It’s a 72 Phs documented real GTO optioned Lemans that has a had a decent frame on restoration. It is a factory 4 speed Muncie car and still retains its original transmission but it now as I ran the numbers has a 1973 400 2brl in it with stock 4x heads that has been rebuilt.

I’m am still learning the car but I have noticed the rebuilt engine idles incredibly smooth with not a hint of a lope. Unfortunately the motor was rebuilt by the owner who the previous owner I bought it from got it from. I have no idea of internals which will make selected a cam difficult but I’m hoping you guys can give me insight.
Here’s what I know:

-the engine runs like silk and you can balance a nickel on the air cleaner
-Pulls strong and seems like make a 14 second car
-410 rear gear

Muncie 4 speed
performer intake ( yes I know the stock 72 intake is better)
brawler 750 carb ( yes I know not a qjet)
converted to hei ignition
headman elite headers
2 1/2 pypes exhaust

here’s my issue. It’s really irking me I do not know what cam it has and it idles like a stock 400 from 73. It honestly has road manner of a stock cam but when I get over 2 grand it becomes incredibly loud and poppy and sounds rediculously nice. I don’t think a stock cam would do that even being forced to wind up. Maybe it’s a 068 cam or a performer cam? What ever it is it definitely has a short duration which make me want to step it up if it’s possible.

So here’s the typically question you have seen a million times.... ram air III cam?

assuming I have 8.5 compression would this combo work well. Also,not sure of the aftermarket support but is there any pistons that work well with the 4x heads guys like to run to obtain 9 plus compression?

I figure with my gears and manual transmission It might work. I’m also a purist and want to be able to say I put a ram air III cam in it even though I could get a much better modern cam custom ground. 

thanks!
Dan


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## PontiacJim (Dec 29, 2012)

What are you calling the Ram Air III cam? The 744? There was a reason why Pontiac ditched it early on. 

First you want to know more about your valve springs. If you go more lift, will they have enough spring pressure to keep the valves from floating off their seats at higher RPM's. So you need to know what springs you have - unless you keep it factory lift and go more duration.

More duration pushes the RPM power band higher up into the RPM range and sacrifices bottom end - and is probably what you are experiencing right now. Go with a bigger cam and you may have a bigger disappointment. The train of thought is that a stock Pontiac head flows best up to about .450" lift and gains little going above that, thus Pontiac uses a longer duration - but this was also with higher compressions and Premium leaded gasoline with 98-100 octane. 

No need to start fooling with head changes and getting higher compression with new pistons unless you are looking for an excuse to tear down & rebuild your engine. Lower compression can be your friend. You want to raise dynamic compression. A Comp Cams cam with 110LSA will do this. I ran the XE274 in a 1972 400 with about 8.0 compression, 3-angle valve job, and my own port match and a basic deburring/clean-up. Pulled like a bear, but fell off fast around 5,500 RPM's which is fine for a stock bottom end engine with cast rods and cast pistons. BUT, it had a higher lift and I purchased matching springs.

Do not know anything about your carb and the Performer is not the ideal candidate for a performance gain - so I would ditch both and begin there with a factory Q-jet and intake.

So food for thought.


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## Old Man Taylor (May 9, 2011)

FYI, saying RAIII cam means one of two cams. The 068 for automatics and the 744 for a manual trans.


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## Thered72 (Jul 30, 2020)

PontiacJim said:


> What are you calling the Ram Air III cam? The 744? There was a reason why Pontiac ditched it early on.
> 
> First you want to know more about your valve springs. If you go more lift, will they have enough spring pressure to keep the valves from floating off their seats at higher RPM's. So you need to know what springs you have - unless you keep it factory lift and go more duration.
> 
> ...


Yes exactly! Thats why I wanted to poke around in the forum and ask some guys with experience like yourself their thoughts. So just for clarification I was only wondering about what pistons guys run because my engine looks like someone put a lot of time and effort into it and I wouldn'tt be surprised if it was more than a basic rebuild and they added aftermarket pistons to boost compression if it were possible. I just wanted to get clarification if this was popular since most build recipes I've seen when I had my Trans Am usually included stock pistons and shaving 6x heads. I was kind of thrown off when I saw they were 4x heads on there and figured if a guy wanted a fast motor in a real gto he would not leave a 165hp engine fro 1973 stock. Anyways, I know the intake and carb are a big no no but it runs so good I am going to keep it for now. 

I did want to ask you a big question here about your cam suggestion because I think I am missing something. Did Pontiac advertise their cams specs differently so I am not understanding the geometry correctly? When I compare the two, the xe 274 has .80 more lift on the intake and exh and is also has a higher duration. I know that extreme energy cams are made for low compression engines which is why I suspect it works so well, but why did your mention that the 744 cam would require new springs because of lift when the comp cam has in noticeably higher? 410 lift is less than a tinny edelbrock performer cam. I must be missing something.

Here's what I am looking at

744- 224/236 dur .410 intake .410 exh 119 lsa
xe 274 230/236 dur .488 intake .491 exh 110lsa

Thanks for you help!


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## Thered72 (Jul 30, 2020)

Old Man Taylor said:


> FYI, saying RAIII cam means one of two cams. The 068 for automatics and the 744 for a manual trans.


I have a muncie rockcrusher so I would go with the 744 i guess. whats the difference in specs?


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## Old Man Taylor (May 9, 2011)

The 068 was 212/225 with 0.407" lift. LSA is 116. The 744 is 224/236 with 0.407 lift on a 115.5 LSA. There's no telling what cam is in your engine since it is not original.


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## Old Man Taylor (May 9, 2011)

I forgot to mention about the valve springs for the 744 cam. It has nothing to do with the lift of that cam. The 744 was the last cam Pontiac made that had a fixed ramp angle (lift profile) on the lobes. The duration was long enough that they ran out of ramp to maintain the 0.407" lift. That made the nose of the cam flat. That caused valve spring problems that required taller and stronger springs. IIRC the factory installed height of springs for the 068 cam is 1.56". For the later 744 cams it was 1.714", and 1.8" for the 041 cam.


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## PontiacJim (Dec 29, 2012)

*Thered72* - "I did want to ask you a big question here about your cam suggestion because I think I am missing something. Did Pontiac advertise their cams specs differently so I am not understanding the geometry correctly? When I compare the two, the xe 274 has .80 more lift on the intake and exh and is also has a higher duration. I know that extreme energy cams are made for low compression engines which is why I suspect it works so well, but why did your mention that the 744 cam would require new springs because of lift when the comp cam has in noticeably higher? 410 lift is less than a tinny edelbrock performer cam. I must be missing something.

Here's what I am looking at

744- 224/236 dur .410 intake .410 exh 119 lsa
xe 274 230/236 dur .488 intake .491 exh 110lsa"

*PJ *- Here goes. Yes, Pontiac, as well as any cam manufacturer can use different lift points on the cam, and this is why they can be confusing when comparing. So the way to compare, and even this can be slightly deceiving, is to compare each cam at its .050" lift spec.

The factory cams were generally spec'd at .006" where it was considered that all the slack in the valve train, ie lifter, pushrod, rocker arm, was taken up and the valve would then begin to raise off the valve seat and duration/lift numbers began. This was essentially an AMA spec which all car manufacturers adhered to as their industry standard. Aftermarket cam grinders were all over the place - and rightly so in an effort to keep secret how they ground their cams and sometimes to sound better on paper than the next guy.

The "744" as Jim Taylor explained it is correct. The lobe actually looks like a roller cam lobe, kinda flat on the top. Milt Schornack ran a RA car with this cam and hated it. He went back to the 068 cam as I recall and the factory seemed to follow his lead shortly thereafter. I enclosed a photo I have showing the differences in the ramps, 744 on the left.

I was thinking off the top of my head and thought the 744 was more inline with the larger lift RA IV cam. Lift is .406" like most all Pontiac cams. I have read that you can go up to about .45-" lift with the stock springs. However, you numbers seem off. The duration Int/Exh is shown to be 301/313. LSA is 115.5. Overlap, another big consideration, is shown as 76 degrees. The 068 for comparison is 63 and the RA IV being 87.

The XE Cam has a higher lift and a faster ramp opening so it requires stronger springs. When I purchased my cam/lifters, I also purchased matching springs. I said the head basically flows up to .450" and may flow slightly more at higher lifts, but there seems to be little gain.

So doing some basic head work will improve flow and take advantage of the higher XE 274 lift. My thinking, and I may be wrong, is that even though the heads don't benefit from lift over .450", that the higher lift cam reaches the .450" faster/earlier on the lobe profile and is then kept open longer as the lobe reaches the high side of .488" and as it drops off on the closing ramp. So if I were to draw a cam lobe and view it from the side and mark at what point on the cam lobe .450" is reached, then went up and over the top of the lobe at .488" and then went down the lobe until I reached .450" lift, and drew a line between those 2 points and looked at the cam lobe, it would look flat on top like a roller cam profile, but I still effectively have a typical flat hydraulic cam lobe. I would then be able to calculate the duration that _my valve_ is being effectively kept openedat its apex Versus simply climbing the lobe ramp gradually to reach the apex of .450" and then drop down the ramp backside. The valve would only momentarily stay at .450" while the higher lift cam would hold the valve open at .450" for a much longer period- understanding that any lift above .450" lift is doing nothing for flow because my heads stopped flowing at .450", but I got more _valve lift duration_ (not cam duration) at which .450" lift was effective.

Hope that makes sense?


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## Thered72 (Jul 30, 2020)

Pontiac Jim sorry about the late response. I was taken back by your great description and had to read over it a few times before I could think of a response. Anyways, after sitting on it for a while I think I’d consider the comp 274 cam. I actually was able to ID my heads and they are the 4x 7h heads so they have the 98cc combustion chambers and 211 intake and 166 exhaust. When I ran my casting number this was a 73 400 2bl with different heads.

assuming I have stock pistons still and now have 98 or less ccchambers what do your think my compression might be at? Also there’s a good chance I have pressed in studs. What mods do I have to make to run the compxe 274?

thank you, you both have been a huge help.


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## Thered72 (Jul 30, 2020)

IMG_1127.HEIC


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## PontiacJim (Dec 29, 2012)

Thered72 said:


> Pontiac Jim sorry about the late response. I was taken back by your great description and had to read over it a few times before I could think of a response. Anyways, after sitting on it for a while I think I’d consider the comp 274 cam. I actually was able to ID my heads and they are the 4x 7h heads so they have the 98cc combustion chambers and 211 intake and 166 exhaust. When I ran my casting number this was a 73 400 2bl with different heads.
> 
> assuming I have stock pistons still and now have 98 or less ccchambers what do your think my compression might be at? Also there’s a good chance I have pressed in studs. What mods do I have to make to run the compxe 274?
> 
> thank you, you both have been a huge help.


Using the Wallace Compression Calculator, I get a compression around 8.17 - .030" over 400CI, 98 cc heads, 6.6 cc valve reliefs, pistons .015" down in the bore, .039" head gasket (Felpro).

Not a lot of compression, but workable. You can mill the heads a little and get thinner Cometic head gaskets to get the compression up slightly more.

Similar to my last 1972 400CI with 7K3 heads (98 cc). I liked the XE274. Ran on pump gas. Nice power up to around 5,600 RPM's.

If you have press-in studs, they can be changed to screw-in studs which a machine shop can do. ARP sells a screw-in rocker arm stud for this application. Then you want to get matching poly-locks to replace the rocker arm nuts and "zero lash" the lifters. You will also want matching valve springs, but discuss your plans with your machinist who will be re-building the heads?

But, you can search around and check out other similar builds. Everyone has a cam recommendation. From my reading and my 400CI experience, I like the 110 LSA for a low compression engine. But, others like 112 LSA which will give a little broader power band. Some dislike the XE line and suggest the VooDoo cams. So it is a crap shoot and I say just pick one and go for it. If you really hate it, Pontiac's are easy enough to swap out a cam and a flat tappet cam isn't a killer price tag like a roller. Sometimes you just have to experiment.


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## Thered72 (Jul 30, 2020)

Jim I love your experience and knowledge. Thanks for getting back to me again with a good answer. So... yes I am aware of the camshaft crap shoot. I had a 79 trans am with a 403 and even you think 400 pontiac cam recommendations are hard think again. I couldn’t get a straight answer from anyone for 2 years on what cam I should go with. I ended getting a voodoo cam myself and called a cam grinder and they agreed that the cam would work well but man, that was a lot of work.
Anyways, 274 xe it is but I do one question. If my motor came with 110cc 4x 4h heads and made 8.0 from the factory wouldnt I have closer to 9.0 since there’s about a 12cc different in volume. Also, we can probably assume since the engine builder sourced better heads they also most likely killed them down a bit for better performance.

what do you think?


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## PontiacJim (Dec 29, 2012)

Thered72 said:


> Jim I love your experience and knowledge. Thanks for getting back to me again with a good answer. So... yes I am aware of the camshaft crap shoot. I had a 79 trans am with a 403 and even you think 400 pontiac cam recommendations are hard think again. I couldn’t get a straight answer from anyone for 2 years on what cam I should go with. I ended getting a voodoo cam myself and called a cam grinder and they agreed that the cam would work well but man, that was a lot of work.
> Anyways, 274 xe it is but I do one question. If my motor came with 110cc 4x 4h heads and made 8.0 from the factory wouldnt I have closer to 9.0 since there’s about a 12cc different in volume. Also, we can probably assume since the engine builder sourced better heads they also most likely killed them down a bit for better performance.
> 
> what do you think?


I agree with your question on the 110 cc heads. I used the variables I listed and plugged them into the Wallace Compression Calculator, _BUT used the 4X 4H heads, not 4X 7H._ I kept thinking I was missing something, and if I was, I could not seen to find it. The '72 400CI with the 7K3 heads and same cc volume shows to be a factory 8.2 compression - so calculating 8.17 compression in my opinion is close enough to 8.2, which is what I got.

The 4X 7H appears to be a performance head with 2.11" intakes & screw-in studs. All you have to do is look to see if you have the screw-in studs. These too are shown to be 98 cc's, so you still look good and I should be correct on the 8.17/8.2 compression ratio.

You can read this article on the 4X heads. It appears they too are 98cc's, but some versions look to be the small intake valves and press-in studs - but not all of them were. They also have the 4X in larger combustion cc flavors.









4X Racing Heads - Tech Articles - High Performance Pontiac Magazine


Check out this tech article on 4X Racing Heads, brought to you by the experts at High Performance Pontiac Magazine.




www.hotrod.com





So if they were milled down, that would raise compression, but the intake side would also have to be milled if they milled them a bunch. Sometimes you can have fitment issues with the valley pan when you mill the head a lot as it changes dimensions/geometry to include the need to measure pushrod lengths and getting rocker arm geometry correct.

Just as an example, you could use the more expensive Cometic head gaskets (about $100 ea.) that are .027" thick, mill the heads to get 96 cc's, and the new compression will be about 8.4. You would want to use a pushrod checking tool just to make sure you have the correct length pushrods so rocker arm geometry is correct. So for the extra expense of the Cometic head gaskets, and possibly new pushrods, you are not really going to feel any big gains. So I would leave well enough alone and have the heads surfaced to clean them up and ensure they are flat and go with the .039" Felpro (I believe they may be listed as .041", but compress to .039") gaskets that usually come in the rebuild kit. Butler Pontiac also has a nice complete gasket set so you know you are getting all that you need - or just get what you need.

Again, with the lift of the XE which has a fast opening ramp, you want to install 7/16" ARP Big Block rocker arm studs to replace the factory 3/8" "bottle neck" studs if you still have them, and use matching poly-locks - which will make this an "adjustable" valvetrain. In the photo, the 7/16" stud looks to have a longer bottom/threaded area, but I think it is just the side-by-side positioning and pic angle. You want to make sure they don't bottom out if replacing. I did not check mine and just put them in. I don't know of any issues, but I should have measured the bottom stud length to make sure - so I am pointing this out. You could grind a little off if needed, but I don't think there should be an issue. Put them in dry & torque.

When you re-install the intake, insert the rubber O-ring seal between the timing cover and front water passage on the intake and torque the long bolt to draw it tight. Then insert/torque the manifold bolts. If you do not draw the intake forward to get a good tight seal on the O-ring first, you may have a water leak. You can put a light coating of sealer on the O-ring.


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## Thered72 (Jul 30, 2020)

Jim, thank you for making this idiot proof for me. So here’s what I know. 

My motor was rebuilt two owners ago. I’m trying to get his contact info to ask him what cam he chose but he is not friendly and doesn’t want to be involved( probably why my car sat under a oak tree for 25 years outside. Typical Nfs I’m gonna restore it someday guy). I do however know the owner I bought it from removed the engine and brought it to a machine shop and had the head taken off and redone and “ shaved” so I probably have 8.5 compression which I’m happy with but I just feel like somethings not adding up here and I keep going back total timing or a weak cam.

Right now with 410s I might be doing zero to 60 and 7.5 or 8 seconds. I had a stock s10 pickup truck almost smoke me which really got me thinking something just isn’t right. After this I got home and put my timing light to it and the motor was at -4 initial timing. I went to adjust the distributor but I realized it was advanced as far as it could go bc the electronic box on the side of the hei was hitting the throttle bracket ( same thing happened to my last Transam that had a performer intake) So of course my dist had to be orientated 180 out. Anyways I fixed this and set it to 16 degrees initial. Reving it to 3500 it’s total timing is 25-26. It’s definitely faster but it didn’t make the difference I thought it would. Any suggestion on what to do next as far as fine tuning?

with good flowing heads and intake and exhaust plus March pulleys and everything else that was added on it I feel like I should be running at least 7 seconds zero to 60 and high 14s. Somethings not right.

parts:

750 brawler carb
March pulleys
Performer intake
Herman elite ceramic headers
Completely welded stainless 2.5 magnaflow exhaust
Better 4x heads then we’re Milled and have 211 and 177 valves.
Unknown cam 

Am I right here? I should be making at least 300 hp but it doesn’t feel like it. I feel like the gears are doing most of the work since it’s geared like a town dump truck. This is also hiding how strong the motor really is.


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## Old Man Taylor (May 9, 2011)

Your total timing is almost 10 degrees less than it should be - unless it's that way to stop pinging from a compression ratio that is too high. I always ran about 36 degrees total with open chamber heads.


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## Thered72 (Jul 30, 2020)

Exactly what I was thinking. Getting the total timing up to where it should be involves more than just advancing the distributor more right? Wouldn’t the orientation of how the cam was installed and the timing chain effect this?


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## Old Man Taylor (May 9, 2011)

No, just advance the distributor.


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## BearGFR (Aug 25, 2008)

Thered72 said:


> Exactly what I was thinking. Getting the total timing up to where it should be involves more than just advancing the distributor more right? Wouldn’t the orientation of how the cam was installed and the timing chain effect this?


Like OMT said, no. Sometimes folks get confused because the word "timing" by itself can refer to two different things in an engine. There's ignition timing, which is talking about when the spark plugs fire in relation to crankshaft position (that's the one that you don't have set high enough) and on our cars that's what you set by moving the distributor. Then there's cam timing, which is talking about when the intake and exhaust valves open and close in relation to crankshaft position. Cam timing is a function of how the camshaft is ground (which you can't change) and also how the timing chain sprockets are installed. On the factory setup you only have one choice there too. Some aftermarket timing sets have multiple keyways in them that allow you to install the cam so that the valves open/close "a little earlier" in the cycle (called advancing the cam, which tends to shift the torque/power curve lower to a lower rpm range) or a little later in the cycle (called retarding the cam, which has the opposite effect).

Here's an example of such a timing set:
https://butlerperformance.com/i-244...tandard-rol-cs-7050.html?ref=category:1234831

Bear


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## PontiacJim (Dec 29, 2012)

Thered72 said:


> Jim, thank you for making this idiot proof for me. So here’s what I know.
> 
> My motor was rebuilt two owners ago. I’m trying to get his contact info to ask him what cam he chose but he is not friendly and doesn’t want to be involved( probably why my car sat under a oak tree for 25 years outside. Typical Nfs I’m gonna restore it someday guy). I do however know the owner I bought it from removed the engine and brought it to a machine shop and had the head taken off and redone and “ shaved” so I probably have 8.5 compression which I’m happy with but I just feel like somethings not adding up here and I keep going back total timing or a weak cam.
> 
> ...


OK, you won't like this but.........

The Performer is the small runner intake and most likely hurting you. The RPM Performer is much better, BUT, the stock cast iron intake and Q-jet is the best as it will equal the RPM Performer which will only give a few more HP over the stock intake which you will not feel anyway. Some will put a 1" spacer on the stock intake and pick up that lost HP. The Q-jet is also a "best choice" for the street. Small primaries develop quick port velocity to cause the engine to snap to attention while the large secondaries pop open and take over - so there is where you will gain.

The 4.10's are a waste on a Pontiac. You can't buzz the engine high enough in stock/mild form to take advantage of them like a 7,500 RPM Chevy small block. Pontiac's make torque and it is torque that moves the car. Torque will make the engine/car work hard, pull, and dig in. With what you have, you are buzzing the engine through it's RPM range so quick that power is being thrown away. I would opt for 3.55's and no more than 3.70's which I feel would still be too much.

Ditch the factory HEI. They were not designed for high RPM's. Yes they put out more spark power, but the advance curves built into them are not good - and as you see, your total advance sucks if it is only 25-26 @ 3,500. You can modify this to make improvements and you can find this on the internet, but it'll take work and trial and error. I would take points over a factory HEI and I don't care what the pro's are. Now aftermarket is another story as these are made for high-performance in mind. I have a Pertronix ready to run distributor which is an electronic HEI, but there are other choices. Note the Pertronix states it has a steel gear which is not good for hydraulic flat tappet cams. You want a factory style cast iron gear or composite. You also want a matching coil. You can read more here:









PONTIAC PerTronix D120710 PerTronix Flame-Thrower Plug and Play Billet Distributors with Ignitor II® Module | Summit Racing


Free Shipping - PerTronix Flame-Thrower Plug and Play Billet Distributors with Ignitor II® Module with qualifying orders of $99. Shop Distributors at Summit Racing.




www.summitracing.com





So if you want to go inexpensive, get an old points distributor and add the Pertronix electronic conversion AND matching coil and make sure you are getting 12V to supply the coil when it is running - ie no ballast wire or resistor to drop running voltage below 12V.

Timing is important and has been covered a ton on the forums. The initial setting and total advance can make or break a good running Pontiac engine.

So those are my recommendations.


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## Thered72 (Jul 30, 2020)

Haha man I was expecting that Jim. This is my 3rd Pontiac and is the reason why even though it ran so good I knew something was up. I’ve only ever ran qjets but never had huge luck dialing them in. Seems like I always rebuild Worn out ones and never had sent one to cliff. Right now since I just got the car I want to get to know it and not dig into it so much. One of the first things I mentioned when negotiating was the carb and intake. They were having a hard time selling the car and I had to explain to them how is Pontiac guys are critical and a lot of common aftermarket upgrades aren’t better than stock and are unattractive to buyers. 

Anyways, I’m still fairly young being 35 and I think this set up gives me a good opportunity to compare and contrast common theories. I’ve always used qjets and stock intakes so I want to have some fun and learn how to fine tune a Holley and see for myself what the hubbub is. Also, thanks for your advice with the timing and rear gears. Gears are on my list of things to do. I was planning on 355s and I also advanced the timing more. I got it to about 30 total timing now and it made a big difference. I actually could hook and not just peel out for days and I also moved the Tourque curve up about 1500 rpm so I got more power where I needed it. I’m just advancing a little at a time and getting a feel for what the engine wants.

thanks also for bringing up the performer rpm intake bc I wanted to ask you about that. Will that clear my hood with a stock dual snorkel air cleaner? It seems tight. Also, as for a stock intake are your reccomending a 72 HO intake? When I checked them out they were serious coin and I’d rather spend half the cash and get an rpm. However, part of me wants to leave the whole motor the way it is bc I don’t know how rebuilt It really is bc I have no receipts to proof it and I don’t know how well bottom end is. I would hate to do a intake and came swap and only run into huge problems and possibly throw a rod or whatever before I get a chance to sell it and move up to a real judge.
Let me know your thoughts.


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## PontiacJim (Dec 29, 2012)

Thered72 said:


> Haha man I was expecting that Jim. This is my 3rd Pontiac and is the reason why even though it ran so good I knew something was up. I’ve only ever ran qjets but never had huge luck dialing them in. Seems like I always rebuild Worn out ones and never had sent one to cliff. Right now since I just got the car I want to get to know it and not dig into it so much. One of the first things I mentioned when negotiating was the carb and intake. They were having a hard time selling the car and I had to explain to them how is Pontiac guys are critical and a lot of common aftermarket upgrades aren’t better than stock and are unattractive to buyers.
> 
> Anyways, I’m still fairly young being 35 and I think this set up gives me a good opportunity to compare and contrast common theories. I’ve always used qjets and stock intakes so I want to have some fun and learn how to fine tune a Holley and see for myself what the hubbub is. Also, thanks for your advice with the timing and rear gears. Gears are on my list of things to do. I was planning on 355s and I also advanced the timing more. I got it to about 30 total timing now and it made a big difference. I actually could hook and not just peel out for days and I also moved the Tourque curve up about 1500 rpm so I got more power where I needed it. I’m just advancing a little at a time and getting a feel for what the engine wants.
> 
> ...


Why spend the extra $$ on an aluminum HO intake when the cast iron does the same deal? OK, so it has the removeable heat crossover under the intake - how often do you think you might be taking it off? Some will simply remove the cast iron heat crossover and then use a block-off plate on the heads to cover the exhaust ports. You can easily gasket port match the intake runners to the larger RAIV size, but there will be a slight port mismatch to the stock heads.

The Performer RPM is 1 1/4" taller, so find a piece of foam or something soft that will compress that is 1 1/4" and put it on top of the air cleaner to see if it touches the hood.

The RPM intake will also have the larger RAIV intake ports which will also be a slight mis-match to the stock heads. Never heard of any complaints as many use the intake as a bolt-on.

So, you can do things in stages like most of do - when $budget allows.

Timing is real important and will wake up the engine. If you hear any "pinging" under hard acceleration, then you have gone too far on the timing and you want to back it down a couple degrees. Many of us "old" guys used to set our distributors this way. Advance it until it "pings" and then back it off a couple degrees and you were good to go.

As you advance the timing, you may want to play around a little with the carb - adjust the idle mixture screws.

Keep playing with it and you will get a feel for making your adjustments.


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## Thered72 (Jul 30, 2020)

Jim which stock intake are you referring too so I can check them out? The ones I saw were around 1200 bucks.


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