I finally got some time to work on the truck again yesterday. The new Vortec 454 is finally sitting in the frame correctly now. Here is what I found on the mounts.
First, I had 3 different engine mounts, or 'cups'. I could tell just by looking the cups on the Vortec were not as tall as the cups that were on the '77 big block that I parted out, or the cups on the '86 305 engine I was replacing. But I couldn't get a measurement without removing then.
So here are the three cups side by side. The left one is from the '77 long bed with original big block, center is from the '00 C3500 Vortec 7400, and the right one is from the '86 short bed with a 305.
The approximate measurement from the block mounting surface to the center of the engine mounting hole for these mounts are:
'00 Vortec - 2-1/8"
'77 454 - 2-5/8"
'86 305 - 2-3/4"
That is only half the story. I also discovered the rubber engine mounts for the 305 small block are different from the original big block mounts from my '77. Here is the picture, look at the lower monting holes on the right side of the pic.
You can see they are spaced closer together both in the horizontal and vertical dimension. This causes them to line up differently with the holes in the mount towers that are on the frame. Unfortunately I did not snap a picture of this.
I first tried using the 305 mounting cups since they were the tallest with the BB engine mounts. After much grunting and cussing trying to get it to line up, I gave up and swapped the cups for the 454 cups out of the '77. Then the motor literally just dropped into place!
Here is the money shot.
I got the 1/2" clearance I was looking for! Yeeee Haaaahhh!!!
And here is the front shot showing both mounts. Notice I used poly bushings that are inserted into the original steel clamshells from the '77 truck. I plan on cleaning up the new small block mounts I bought and trying to exchange them for big block mounts.
