[Jhankins]

I'm looking to buy an exhaust kit for my 77 GP 400ci. I still have the stock manifolds on it. Does anyone know where I can buy a manifold back kit? Or will I have to get a custom build? I understand I will most likely need to replace the trans crossmember but that is not an issue. TIA!

[gtospieg]

Have you checked with Pypes? Maybe they offer a system or can tell you if one of the A body systems will work. If you buy a Pypes system and retain exhaust manifolds you still need to buy down pipes to connect to the rest of the system.

[Jhankins]

gtospieg, Thanks for the info I will check with them.

[gtospieg]

Jhankins...No problem...we are here to help.

[NorthcoastGP]

If you're looking for a stock type, Classic Exhaust in Geneva, OH might be able to help. I installed their dual exhaust system on my '74 GP and I am pleased with the results

[jerry455]

When I had my 1977 Can Am, I had to replace the trans crossmember to a 1973-1974 style. 1975 and newer had a catalytic convertor and the exhaust ran on the passenger side of the car. There is no hump on the driver side of the stock crossmember for the driver side exhaust pipe to pass under. There never used to be a kit to convert a dual exhaust on the newer, 1975 and up, because of the penalties for removing emissions controls. I originally had an exhaust kit for a 1973 GTO on my Can Am. It is probably the same as the Grand Prix, Grand Am and Lemans. You might be able to modify your stock crossmember if you are able to weld. I did that for my 1986 Grand Prix.

[Sirrotica]

Pontiac also did one more thing to defeat putting duals on cars that came from the factory with single exhaust and a catalyst. They changed the exhaust flange and manifolds from 2 bolts, to 3 bolts. It's not that big a deal to switch flanges from the crossover pipe to the new pipes if the flange can slide all the way back to where the muffler connects. If the new pipe has any wide spots that a flange can't be slid all the way off the end of the pipe your gonna have to do some other procedures.

If you can't slide the flange off and on, you could have to cut the flare off to swap flanges, then re weld it back together. Been there done that before. It's not fun cutting a new pipe up, then welding it back together, but you have to have the 3 bolt flange to match the later manifolds. If you end up having someone bend pipes for you, make sure they put 3 hole flanges on them before they flare the engine end.