need some help 455 in a gbody

[SafariWagon]

400 pontiac swap

I just yanked the V6 and I'm mocking up the 400 Poncho this coming week. I am trying to use 2nd gen f-body motor mounts and block brackets along with Summit's cheap $105 dollar headers. I may have to cut and modify them? I'll just order J bent 1 5/8 tubes from Summit to do this if it's required. Just piece it together. You know like those boneheads do if you've ever watched OCC on the Discovery channel. Those guys aren't rocket scientists! I give an update later next week. I'm really going to be pissed if this Poncho turns out to be a dog as a SBC is a drop in. Just doesn't seem right in a Pontiac, to me anyway.

 

[84GP455]

Never mind trying to fit headers in it, just get a pair of factory Pontiac cast iron manifolds and bolt them on and forget about them! I put a 455 in my 84GP in 1990 and haven't had a leak or had to change them since! If i ever do decide to change them i would upgrade to the Ram Air manifolds which flow better and like Grant's Prix says, they flow just as good as tube headers!
But as far as headers go for the Pontiac G body's they do make them but as some people have said, they fit fine on the passengers side but forget about an easy fit for the drivers side. The steering column and the A frame get in the way.

 

[ligoatpar]

Pontiac in a 'G' body

Use the Pontiac 301 block mounts and the replacement frame mount. The 'F'' body block plate will put the engine to high. Early 'A' body headers "supposedly" only need 2 tubes modified. I'm checking on this. Early "A" body manifolds work otherwise. Or 70-81 "F" manifolds. Headers from the 70-81 "F' bodies don't come close to fitting. Lotsa luck with you're project.

 

[86cutlassrules]

What hits on the F-Body headers? when I put the 403 olds in my 80 T/A I remember the application on the headers being both F and G body think it was F 77 - 79 and G body 78 - 80 something, and in summit it was the same part number for both cars. Not saying anybody is wrong, just curious how for an Olds motor it fits both but a Pontiac which is not as wide it doesn't?

 

[jimmyp618]

I just put a 455 buick in my 84 camino and i used headers for a 67-74 skylark , they fit like a charm no mod needed , Took a few weeks to find a set of buick headers though . I would imagine there are some out there for pontiac. Try hooker super comp long tube , only thing is you do have to weld one pipe on each side yourself.

 

[SafariWagon]

F Body motor plate?

The F body motor mounts and engine brackets appear to keep this engine plenty low to me. I was actually surprised how low it is. I could probably run just about any intake I wanted. Carb is sitting level both directions and transmission is mounted with a Jegs's double hump crossmember. I will have to modify 1 tube on each side. If the motor were any lower I think my driveline angle would be screwed up.

 

[ligoatpar]

Headers

What hits on the F-Body headers? when I put the 403 olds in my 80 T/A I remember the application on the headers being both F and G body think it was F 77 - 79 and G body 78 - 80 something, and in summit it was the same part number for both cars. Not saying anybody is wrong, just curious how for an Olds motor it fits both but a Pontiac which is not as wide it doesn't?

The 70-81 Firebird headers hit everything! I was using the 2" dia. round port style for Pontiac. Believe it or not the Firebird subframe is wider than the "G" body frame. The standard "D" port 1-3/4 dia. header may be a closer fit, but I wouldn't take the chance. The 64-67 "A" body frames were narrower than the 70 up firebird subs. I've had more than a couple of people tell me that the 64-67 "A" body headers need 2 tubes cut and modified to fit. One on each side. The Olds 403 shares the same block deck height with a 350 and 307 Olds. The Pontiac deck is higher on the 326 thru 455 engines. That would make a difference with headers. The deck being higher tranlates into the engine being wider with the heads in place. performanceyears.com has a great site for all you're pontiac related questions.

 

[SafariWagon]

400 Pontiac in 81 lemans Wagon

Each application can be different. Not all headers are made the same. Obviously they can can differ from brand to brand . If you're trying to get 1 3/4 or worse yet 2" primary tubes to fit, it will be way different than my application. I am putting a 75 vintage Pontiac 400 with a 77 Turbo 400 in my 81 lemans wagon. I used a Jeg's Th-350 double hump crossover. Cut the transmission mount off the front flipped it to the back and it lined up perfect. Bolted the motor mounts on block and dropped it in. Placed Summit 1 5/8" primary tube ($105 version) in from the bottom. Dropped the heads on from the top with intake. Put a level on carb flange. Amazingly perfectly level both directions. Checked header fitment of the Summit F body headers. Driver side tube hits the firewall and passenger side hits the lower A-frame . Cut and splice 1 tube on each header. Grind smooth and paint. I am pretty surprised how well it did work out. If anything I don't think I could go lower anymore. Maybe back slightly but not more than an inch MAX. So I am leaving well enough alone.

 

[ligoatpar]

455 pontiac in 'G' body

That sounds like a great install. Thanks for the input about the headers.

 

[shotgun]

ligoatpar, you need to drive that Wagon up to my shop, I live and breath Pontiac.

Small world, I grew up in Southhampton and now live Willow Grove.

I stumbled out of "Kenny's" many a night. :lol: