changing motors

[buba198]

i have a 78 lemans with a chevy 350 i have a pontiac 455 i want to put in but what do i do for motor mounts i know jegs sells a b.p.o. transmission adapter plate thanks

 

[Blake442]

I believe that the factory mounts for a 301 will work.

 

[mguerci]

All Pontiac V8s (including 301) were made with the following mounting patterns:

Pre-1970 blocks: 2 holes per side
1970-1976 blocks: 5 holes per side
1977-1979 blocks: 3 holes per side

If 455 your block is newer than 70, then the stock 301 mounts will work fine. If it is older, then you will need adapters. Adapters are available from a number of Pontiac sources.

 

[BrownGP83]

I don't believe the 455 was made before 1970, so that should not be an issue. Some of the blocks with 5 holes may not have all the holes tapped either, but the ones i have seen were the old 2 bolt mount that were not, so the 301 mounts still work. Does anyone make new Pontiac engine/G-body mounts, or are we still left scrounging junkyards and swap meets?

 

[midwestls]

I can't say for Pontiac but I know Buick's 455 came out in 70. Before that it was a 430. I'd like to think Pontiac may have been the same?

 

[BrownGP83]

I may not be exact on that. 455s could have come out before 1970 in Pontiacs too. I am no expert by any means! I'll admit it!

 

[midwestls]

Me too

 

[mguerci]

I checked and all 455 blocks were made in 1970 - 1974. Therefore, all 455 blocks should have 5 mounting bosses on each side. This means that it will fit with your 301 mounts. I would just do a sanity check on how many bosses are on each side.