my friend wants to swap the ponitac 350 in his 71 firebird with the 428 out of a 68 grand prix. what problems should we expect if we do it. ive been told ponitac changed teh motor mount bolt location on the blocks inbetween the two years is this true. would the exhaust manifolds off the gp wirk on the bird.

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Keith
85 Berlinetta WS-6
87 Cougar 20th Anniversary

 

I think the only differance between those years is potiac added two more holes for different mounts and vehicles. The gp manifolds should work as well as the 350 manifolds and you can get headers for this too. externally there's no real differance between pontiac engines except the 301.

 

if they added extra bolt holes tothe motors does the bird use the same ones as teh gp or the extra ones. also if its the extra ones is there a adapter.

 

1969 and older Pontiac blocks used a 2 bolt motor mount. For 1970, they added 3 more holes for use in the Firebird. So, the 1970 and up Firebird requires a block with the 3 bolt mount which the 428 won't have. You will need a conversion kit. You can get one from Year One, Classic Industries, Performance Years, and Indian Adventures. A 1970 and up 5 bolt block will bolt in any year Pontiac. Some late 70s blocks only had the 3 bolts and need the adapters to work in a 2 bolt chassis. The swap would be well worth it; 428 Pontiac make big power with little mods. For more info on Pontiac motor mounts check the August 2000 and April 2001 issues of High Performance Pontiac magazine.