need some help 455 in a gbody

[buba198]

i have a 78 lemans and the 350 chevy dosent cut it for me so of course the pontiac 455 was the next step but i cant find headers anywhere i am told hooker makes a set of super comps for a g body 301 that should work thanks to the standerd block factor but i cant find them or a part number anywhere a little help would be sweet

 

[G_Body_Enthusiast]

i didnt know they even made headers for the 301. the closest you might get are headers for an f-body.

i did a few google searches and came up with nothing for the application.

the closest i saw was pontiac engine headers for a 79-81 firebird. those will probably work.

 

[78_G_Prix]

i have a 78 lemans and the 350 chevy dosent cut it for me so of course the pontiac 455 was the next step but i cant find headers anywhere i am told hooker makes a set of super comps for a g body 301 that should work thanks to the standerd block factor but i cant find them or a part number anywhere a little help would be sweet

I put a 455 in my 78 Grand Prix a couple of years ago and it was a tight fit. I had to use exhaust manifolds. Chief Many Horses used to make pontiac headers for the 78-87 G-Bodys. I found them a while back, full length stainless headers, but they were in the $600 range. I don't know if they still make them. You may have to get a set of cheap headers and 'tweek' them a little to make 'em fit. The other option most people push is RAIV manifolds that are about as close to a header as a manifold can get (for Pontiacs).

 

[shotgun]

301 headers will bolt up but the block deck is lower ( compared to the 455) they will most likely need to be modified.

That's the killer of this swap,since IA went t*ts up no one makes headers.

I have custom headers in my Pontiac powered Cutlass.

What is your goal?

We pushed a 4300# car into the mid 12z with long branch manifold that are similar to RA manifolds.

If you need any advice let me know.

 

[BrownGP83]

Summit racing carries Hedman shorty headers for Pontiac engines in 2nd gen F-bodies. These might be easier to make work than full length headers. Check their fittment notes first to make sure you won't run in to other problems. I have no experience with these headers myself, just helping look for options.

 

[78_G_Prix]

Summit racing carries Hedman shorty headers for Pontiac engines in 2nd gen F-bodies. These might be easier to make work than full length headers. Check their fittment notes first to make sure you won't run in to other problems. I have no experience with these headers myself, just helping look for options.

I have a set of the Hedman shorties for my swap (455 to 78 GPrix), they didn't fit. It's been a year or two, but I think the driver side fit ok, but the flange on the passenger side hit both the brake lines and the upper A-arm mounts. The flanges would have to be about 2" longer to clear.
Unfortunately I sprung for the cereamic coating before checking fit... expensive lesson learned. I don't know how similar your front suspension is to my Grand Prix, but I would imagine you may have similar troubles.

 

[BrownGP83]

I don't know about the difference between a 78 Lemans and a 78 GP, but they should be pretty close i would think. I thought about them for my 83 when i swap to a 400 Pontiac, but now i know better. Will older A-body headers work? The front suspension looks close to that on a G-body.

 

[bobspacin80ta]

I used full size 74 -77 gp headers for my 78. Only one tube on the pass side had to be dimpled.

 

[grant's prix]

Repro RAIII Manifolds

I used the repro RAIII manifolds in my 1980 GP, clear everything, won't crack or leak, and HPP mag did a story on all the exhaust options about 10 years ago and found the RAIII flow the same as 3 tube headers, a loss of under a second in the 1/4 mile.

 

[KrisW]

I would buck up for the repro manifolds as well. the weight is the only issue because performance gains are offset with headers as soon as you "dimple" a tube or two to make them fit!

You could use the torch and a hammer to clearance the area needed and run the B-body headers or F-body headers, but man that's a lot of work!

Those manifolds are awesome...