[70geeteeohh]

I have my 70 GTO apart cleaning and painting the frame. When I get aroung to it I will be using a 1968 428 4 bolt engine block for the base of my build.

I am aware 400 and 455 frame mounts are different. So what frame and engine mounts would I need for this combination. Pictures would be appreciated if possible.

Thanks as always!

[b-man]

Use the same mounts as a 350 or 400.

455s did have their own special wider frame and engine mounts but the 455 can be installed using the 350/400 pieces.

All the 1964 - 1972 V8 frame stands and engine mounts are the same, so they will accommodate 326, 350, 389 and 400 engines as well as working with 421, 428 and 455 engines.

Had a ‘73 455 in a ‘64 Tempest and a ‘74 455 in a ‘64 GTO and currently running a ‘64 421 HO in my ‘64 Le Mans convertible using the original 326 frame stands and excellent original 1968 400 mounts I had in my stash.

So yes I’ve done 421 and 455 swaps into A-body cars using the non-455 mount pieces.

[70geeteeohh]

Good information. What years did the engine blocks change the bolt holes on the block?

I read somewhere about older blocks not having enough holes and needing a special engine motor mount bracket? Not sure if that pertained to my combination.

[b-man]

Doesn’t apply to your situation.

The adapter mounts are used when the earlier 2-bolt mount blocks (like your 428) are transplanted into later second-gen Firebirds.

455 blocks have the correct 5 bolts per side to accommodate mounting in big Pontiacs and the later Firebirds. Not sure exactly when the change was made but generally 1969 and down blocks had only 2 bolts for mounting on each side.

[70geeteeohh]

Originally Posted by b-man

Doesn’t apply to your situation.

The adapter mounts are used when the earlier 2-bolt mount blocks (like your 428) are transplanted into later second-gen Firebirds.

Great. Thanks for your help