Big Block

[eddie1]

I realize there are a ton of threads dealing with installing a big block & I think I have read everone without finding an answer to my question. I have a 63 1/2 ton, I have added a crossmember from a 80 1/2 ton. I have notched the frame to install the stock motor mounts from the 1980. When the holes line up on the top of the frame rail the holes do not line up with the crossmember. When the holes line up with the crossmember the brackets sits about 1/2 inch above the top of the frame. What is the solution? I am thinking mount the bracket to the top of the frame rail & drill 2 new holes in the crossmember. What have others done? I want to spend as little as possible (don't we all) & I prefer the look of the factory type brackets over the aftermarket tubular style.

[Captainfab]

The '73-'87 motor mount brackets from the C10's are too tall for a good fit to these older frames. The motor mount brackets from the '73-'87 C20's are a better fit. I know it sounds backwards, but the frames on the C20's in the engine compartment are shorter than the C10's. With either bracket, you will have to drill holes in the frame to bolt them up.

Also, with a big block in these trucks, you will need to trim the top flange of the frame for either exhaust manifold or header clearance. I use the '73-'87 frames as a reference as to how much to cut.

[eddie1]

I have trimmed the frame rails already but I thought I could using the existing holes in the frame.

[Captainfab]

No, you have to drill holes in the frame. With a big block, I don't know if you can bolt them to the crossmember and drill the frame to bolt them down. With a big block, you will have the possibility of firewall clearance issues. I would suggest checking out protrash64's thread in the 'Projects and Builds' section on his big block install in his Suburban. He used that style of motor mounts. On my Suburban, I built my own motor mount brackets, since I wanted to move my engine forward 2".

Originally Posted by eddie1

I have trimmed the frame rails already but I thought I could using the existing holes in the frame.

[eddie1]

Originally Posted by Captainfab

No, you have to drill holes in the frame. With a big block, I don't know if you can bolt them to the crossmember and drill the frame to bolt them down. With a big block, you will have the possibility of firewall clearance issues. I would suggest checking out protrash64's thread in the 'Projects and Builds' section on his big block install in his Suburban. He used that style of motor mounts. On my Suburban, I built my own motor mount brackets, since I wanted to move my engine forward 2".

Thanks for the help!

[Captainfab]

Here's protrash's thread I was talking about. I now remember that he drilled new holes in the crossmember since he was using the C10 motor mount brackets.

http://www.67-72chevytrucks.com/vboa...=272654&page=9