Pontiac 455 Questions

[87PontiacGP]

All 400's are roughly the same except for compression ratio and that is dictated by the heads. A stock '67-'70 4 barrel would be like 10.5 to 1 ratio and anything after '71 would be 8 to 1 or less. '71 -'72 heads are missing the end exhaust manifold bolt holes and require a beveled surface to seal. A '73 would be the first year for EGR in the intake manifold. Pre '70 engines have 2 motor mount holes on the side of the block and post '70 have 5 holes. To use the '78-'81 A/G body 301 mounts to put a 400 in our cars the 5 hole blocks are easiest to work with, although adapters are available to use the 2 hole blocks. '67-'69 F and B body exhaust manifolds dump wrong for our cars and '70 up F-B-A-G manifolds are correct. I say that because headers are rare to non-existent for a 400 in our cars.

Hm, thanks Bonnewagon. So by what you have said, a 1970 on up engine would be easier to work with fitment wise in our cars? If so, that would probably be the better choice for me. Though, I'm going to guess the heads would need to be replaced/modified to accomplish my hp/trq goals? I know Pontiac engines don't like too, too high of compression (or letting the RPM's running too high) compared to other GM sister engines (I've heard 9.5:1 is about as far as you should go, unless I've read wrong..), but I'm not sure how much would be enough for me to achieve my 450-500hp+/500trq+ goal. Unless, the heads would be ok, and I should be looking into other replacement parts first? However, from what dogshit has said, it almost sounds like I should replace the heads for my goals. :?

Like I said before, Pontiac engines are a new realm for me, and any information anyone can give to help me push a 400 to my goals would be greatly appreciated

 

[Bonnewagon]

Yes, Pontiacs are way different from small Chevies. The longer stroke doesn't like high rpm's and the heads/valves were designed to work well with low lift cams. Not that 500 hp isn't doable, it is, but like any other high winding motor you'd need forged rods and pistons, properly prepped crank, better oiling, high compression aluminum heads, better intake, etc, and all that costs money. I'm just saying that Pontiacs were designed to make a LOT of power at lower rpm's and that takes some rethinking on your part. In our cars, a decent (run-of-the-mill) GTO or Trans-Am or big car 400/455 motor is plenty of power. By that I mean a basic low compression 400/455, stock 4 barrel manifold, Q-jet carb, good exhaust and a strong cam is really all you need. I would aim for that, and if you crave more, then build a screamer.

 

[tdvick]

As Bonnewagon said, any 70 and later block would be a direct fit. I would say, if you have a choice, pick a block from 70 to early 75. 70 blocks are casting number 9799914. These are good blocks. All 71 to early 75 blocks were casting number 481988. Again, these are all good blocks. Late 75 through 79 are casting number 500557. These later blocks are a bit thinner and not quite as strong as the earlier blocks. These blocks are fine for a street build, but if you have your choice, I'd pick the earlier block.

 

[BuickOldsPontiac]

I would also recommend that you pick up a copy of How to Build Max Performance Pontiac V8s and How to Rebuild Pontiac V-8s. Both are well written and easy to understand. They will have you speaking fluent Pontiac in no time flat.

8)

 

[87PontiacGP]

Yes, Pontiacs are way different from small Chevies. The longer stroke doesn't like high rpm's and the heads/valves were designed to work well with low lift cams. Not that 500 hp isn't doable, it is, but like any other high winding motor you'd need forged rods and pistons, properly prepped crank, better oiling, high compression aluminum heads, better intake, etc, and all that costs money. I'm just saying that Pontiacs were designed to make a LOT of power at lower rpm's and that takes some rethinking on your part. In our cars, a decent (run-of-the-mill) GTO or Trans-Am or big car 400/455 motor is plenty of power. By that I mean a basic low compression 400/455, stock 4 barrel manifold, Q-jet carb, good exhaust and a strong cam is really all you need. I would aim for that, and if you crave more, then build a screamer.

Thanks for that again, Bonnewagon. In truth, I think 450hp would be plenty for me in all honesty (hell I think 350hp would be damn fun in these cars too from what I'm used too..). This will be my frist big block car, and I was ironically going to go the route of: 400, 4bbl Qjet (or if I could, us the stock CCC Qjet), stock manifolds, hotter cam, and maybe an intake. Not sure how much hp/trq that would land me (most likely depends on the cam, Qjet setup, and the heads used), but if I could get anywhere near 400-450hp and wherever torque falls I'd be happy I'm sure. The 500hp was more of an "if I could do it within my means" sort of thing. If 500hp or even 450hp wouldn't be a realistic thing to achieve for now and within my current means, I'll have to rethink my current goals and go with what is more doable. Thanks again.

As Bonnewagon said, any 70 and later block would be a direct fit. I would say, if you have a choice, pick a block from 70 to early 75. 70 blocks are casting number 9799914. These are good blocks. All 71 to early 75 blocks were casting number 481988. Again, these are all good blocks. Late 75 through 79 are casting number 500557. These later blocks are a bit thinner and not quite as strong as the earlier blocks. These blocks are fine for a street build, but if you have your choice, I'd pick the earlier block.

Thanks, I think I remember reading that somewhere online, that the older 400 blocks were thinner and not as durable. Even though my engine build is more for a street car, I'd rather have the security of having a more durable block and not need it, than to have a thin, breaking block and need it stronger.

I would also recommend that you pick up a copy of How to Build Max Performance Pontiac V8s and How to Rebuild Pontiac V-8s. Both are well written and easy to understand. They will have you speaking fluent Pontiac in no time flat.

8)

Thanks, I was thinking about picking one, or both, of them up. I have one for SBC engines, but should probably pick one up for Pontiac engines.

If anyone has any build suggestions, I'm all ears.

 

[Bonnewagon]

I think you are on the right track. A basic 4 barrel 400 is almost overkill in our cars and will outperform even modified small blocks. That is because it is designed to pull hard right from idle and move a ton of sheet metal like a full size Catalina and still handle stop and go traffic without overheating. HO Racing's book "Pontiac high performance engine design & blueprint assembly" was and is the Bible of Pontiac knowledge and is worth tracking down. Here is a small section posted on Wallace racing's website (http://www.wallaceracing.com/index.htm) which is another great source of info. http://www.wallaceracing.com/enginetheory.htm Pontiac (as well as Buick, Chevy, and Olds) designed their big motors as a total package to get a certain job done- move a huge car or truck.They used low revving long stroke motors to produce gobs of torque and still last 100,000 miles or more without issues. Buick especially was the under square torque king with it's 350 and 455. It is not a coincidence that the Chevy 400 found in full size cars of the early 70's has the exact same bore and stroke as a Pontiac 400. Of course hot rodders have figured out how to get insane HP numbers from these grocery getters, but like I said before, speed costs money. How fast can you afford to go?

 

[87PontiacGP]

I think you are on the right track. A basic 4 barrel 400 is almost overkill in our cars and will outperform even modified small blocks. That is because it is designed to pull hard right from idle and move a ton of sheet metal like a full size Catalina and still handle stop and go traffic without overheating. HO Racing's book "Pontiac high performance engine design & blueprint assembly" was and is the Bible of Pontiac knowledge and is worth tracking down. Here is a small section posted on Wallace racing's website (http://www.wallaceracing.com/index.htm) which is another great source of info. http://www.wallaceracing.com/enginetheory.htm Pontiac (as well as Buick, Chevy, and Olds) designed their big motors as a total package to get a certain job done- move a huge car or truck.They used low revving long stroke motors to produce gobs of torque and still last 100,000 miles or more without issues. Buick especially was the under square torque king with it's 350 and 455. It is not a coincidence that the Chevy 400 found in full size cars of the early 70's has the exact same bore and stroke as a Pontiac 400. Of course hot rodders have figured out how to get insane HP numbers from these grocery getters, but like I said before, speed costs money. How fast can you afford to go?

Good info, thanks. Sometimes I forget our cars are fairly light compared to the cars these engines came in. When I do get a 400, the first thing I'll be doing is tearing her down and inspecting everything. After that, buying the performance parts I need to make her go. Like I said before, probably going to go simple for now. A cam swap, make sure the heads can handle the cam I'm using and modify springs if needed, maybe different intake, and probably would be done with that. If need be I can save up for different heads. Are aftermarket the only way to go for heads? Shame I can't find any headers for these engines though, unless I haven't been looking hard enough?

 

[Bonnewagon]

No, they used to make them but that's gone away. A set of HO/Ram-Air exhaust manifolds is another way to go. And don't discount the factory intake, it is a very good design and you really have to be pushing it to need more. A friend has 400 with all forged internals and an Edelbrock Torker with a crazy cam and while it is very fast, it is also not very streetable. While very good Pontiac heads are out there, by the time you find a set and build them up, you could have had the Edelbrocks. Most Pontiac heads flow very well up to .450" of lift and I've even gone past that on stock springs. Recent testing by Rocky Rotella and others has found that many stock Pontiac heads and intakes flow almost as well as the so-called "exotic" models like the RAIV's.

 

[87PontiacGP]

No, they used to make them but that's gone away. A set of HO/Ram-Air exhaust manifolds is another way to go. And don't discount the factory intake, it is a very good design and you really have to be pushing it to need more. A friend has 400 with all forged internals and an Edelbrock Torker with a crazy cam and while it is very fast, it is also not very streetable. While very good Pontiac heads are out there, by the time you find a set and build them up, you could have had the Edelbrocks. Most Pontiac heads flow very well up to .450" of lift and I've even gone past that on stock springs. Recent testing by Rocky Rotella and others has found that many stock Pontiac heads and intakes flow almost as well as the so-called "exotic" models like the RAIV's.

I was looking into probably getting a set of Ram Air headers previously. How well do the stock manifolds flow verses the HO/Ram Air sets? Well, if the stock intake will work, then I'll most likely be saving some money and skipping that option (same with the stock manifolds, if they don't restrict things too much.). With heads, I've been checking prices on them, and they are not as bad as I thought they would be. For the Edelbrock heads anyway. Question with the heads though, would 87cc combustion chamber be ok to run (or even 72cc combustion chamber..)? Don't want the compression to come up too high, as I know these engines don't like it. Also, I probably should have been asking for 450-500ft/lb torque numbers instead of hp all along.. After skimming on the 400, I don't think 450 torque number should be too hard to achieve.

These are the heads I was looking at: http://www.summitracing.com/parts/EDL-60579/

Cam is another thing I need to look into also..

 

[Bonnewagon]

The HO/RA exhaust manifolds are scarce but reproductions are made that flow even better than the originals. The stock log type are not very good but a big car 455 manifold would be better than a 301 manifold. Those Edelbrock heads are round port, so round port exhaust would be indicated. Plenty of cams are available, from mild to wild. My last 400 had a Crane 278HMV and was very strong. It needed a vacuum can for the brakes and full manifold vacuum to the vacuum advance to idle well. But it pulled like an ox.