hey, i have a 1971 455 h.o. pontiac with the 2inch intake valves....it was running as of last year, but i will be rebuilding it.... i want to make a streetable 550+ hp..... how can i reach this goal on the engine alone? what carb should i use, intake, cam, ect....

also, what tranny would be good behind something like this? i kind of want a manual but a auto is ok too.....

 

demon is always a good choice for carb, as far as intake/heads/cam it all depends on what rpm you want. for low cost you can get a peak of 4500rpm but you'll never reach that horsepower at that rpm. with higher rpm you need to look at forged crank/rods/pistons. and you'll need an indepth balancing to handle the higher rpms as well. if you don't have alot money just go for a low rpm torque monster.

 

On a Pontiac motor you need big $$$ if you want to twist on it. What are you putting it in? A 1/4 mile goal is alot better to go by than some specific horsepower target since Pontiacs are known for lots of TORQUE. What's your budget?

 

well, i know that the ponchos dont do well after 5500 rs on the stock internals..... so its gonna be pretty much a torque monster that im after..... its going in a fox body mustang thats tubbed and has a tube frame..... weighs 1500 lbs.... im looking at prolly under a grand....

 

you just said the phrase of death. Them are fightin word!....

 

2 things,one your achilies heel is your heads but unfortunately your only real choice are more expensive edelbrock heads so save your money and invest it there,youll get a mor ebang for your buck than a slighty better manifold or carb.just a reality of owning a pontiac..2 ,i thought this was a z28 forum????

 

not completly true. We took the stock heads off a 69 GTO and our motor is pushing about 650hp NA. But thats with about a .660 lift cam and 11:1 compression. The heads are also have stock valves and no port work.

 

You have discovered the force, my friend, the Torque Force!!

If you have a true 71 HO and it is complete, you have some heads that are extremely desirable to collectors, selling them would help fund your project. They have 2.11/1.77 valves and are round port exhaust. Their drawbacks are that they are a bit soft in compression and the intake ports aren't the best. For a modern performance buildup, I would leave these out of the equation. In fact, don't use any 455 head. Pick up a pair of more common 400 6X heads, which have the standard D-port exhaust and much smaller combustion chambers, and flow as well as 455 HO heads. They are a boatload cheaper, so selling the HO heads can be used to fund your project.

For over 500 HP, the factory crank and rods are fine. Going .030 over is recommended to square up the bores and it'll also bring you to 462 cubes. Many 71 455's came with a nodular iron crank, which is much stronger than the standard cast crank. Whichever you have, grind it .010 under on the mains/rods to take some off some excess weight off that porker!

You will have to generously port your heads to get the CFM needed for your HP level. 455s have always suffered with subpar CRs. After 1971, most 455s came from the factory with less than 8:1! With 6X heads, deck them .030, depending on your head gasket this will get your CR in the neighborhood of 9.5-10:1.

Cam selection is quite large, Comp Cams is awesome in helping you select what you need for your application.

You'll need a Victor intake for Holley or Doug Nash if you want to run a Q-jet. The 455 likes ALOT of carburetor, an 850 CFM Holley will work wonders!

Poncho people to talk to: Kauffman Racing, Butler Performance, Rock and Roll Engineering. (Butler recently built the most powerful setup short of a Top Fuel Hemi: A twin turbo Pontiac putting out almost 3,000 HP!!) If you really want to crest that 550 HP mark, don't go Edelbrock, Kauffman offers a comparably priced head with fast-burn combustion chamber technology and D port exhaust so you don't have to modify your headers.

Good luck!

 

if the stang really weighs 1500lbs then you won't have to go crazy to get big power. what casting number are your heads? You can run a late 70s 6x head & get good results. There are 3 different 6x castings (350, 400, 455). Avoid the 455 (LOW compression) heads. 350cid 6x heads are what I'm running on my '66 lemans with very good results and around 11:1 compression. With a budget of $1k you can forget about any fancy aluminum heads. Start with a good casting & get some quality port work.

 

How do i tell for sure which heads i have?? This engine was in a 67 GTO but it originally came from a 71 trans am..... the block numbers correspond with this info, and when i ran them they came up with the 71 455 HO... pretty sure that the guy i got it from didnt switch the heads.... but i need a way to tell for sure....... the heads do have the circular exhaust ports, i noticed that right away. I got the engine for free lol the guy was restoring the GTO back to original engine and gave me the 455. . it runs fine too...

So u guys think that my best bet would be to get some 400 6X heads to bump the compresion?

Yes this is a Z28 forum..... but the 455 might just have to go in one of my 3rd gens im not sure yet....

 

Damn, good deal on the HO! If you have round port heads, they are either RA IV (definitely worth building-high CR and flow awesome) or 400/455 HO. I would prep those heads and get 'em on the market!

6X heads were intended by Pontiac to be an exclusive 400 head. Very, very rarely, I have heard of them being found on 455s but only the open chamber design, very similar to 455 4X heads. I haven't heard one case of these heads found on a 350, and shouldn't as Pontiac never intentionally installed them from the factory. Regardless, the important thing to check is the combustion chamber size. There were 3 different sizes: closed 98cc, open 112 and 115cc chambers. You will need the 98cc heads. Without pulling out my casting # books, I can't tell you which cars/years to check for these heads, but they were produced '76-'79. I would check Ebay for these heads as they can be found dirt cheap, just verify with the seller that they are 98cc chambers.

Yes this is a Z28 forum, and if I had a Z28 it would have a Pontiac under the hood!

 

where are you located, I have a set of 6X heads off a 77 formula 400/4spd, were gone through before I sold the car, new guides, 3 angle valve job, ect., I have been meaning to cc them to check the size

 

Im located just south of duluth/superior.... in wisconsin.

The engine is positively a 455 H.O. the numbers match and its stamped in the side of the block... just worried about the possibility that someone might have switched the heads.

So, the 6x heads with the 98cc heads will bump up my compression to what ratio???? these will flow enough in stock form to support my engine, or do i need to have them ported..... also, what lift cam can they support? (the reason i asked is on my 87 formula we could only put in a cam with a .510 lift without machining the heads and i dont want to run into that problem again, sorry for the newb question )

 

I just know for sure about there being 3 sizes of 6X heads. I thought they were used on 350s too, but it's not something I can argue about.

I'm not sure about bumping the compression. What kind of gas are you willing to live with?

BTW, do you want to sell that 455HO setup?

 

Well, everything is for sale for the right price..... but im not too intent on getting rid of it right now, kinda wanna put it in something.

also, i would like to be able to run my setup on pump gas..

does anyone know of some sites that sell pontiac performance parts, and have head casting number listings?