BBC vs SBC motor mounts - they are not the same

[Mr.Chevy4x4]

Well, after much fussing, cussing, and general aggravation....it finally dawned on me what my header fitment issue was. I pulled out a set of known SBC mounts (engine side) and compared them to the BBC mounts that were on my fresh engine. I know these to be original big block because I know the truck the engine came out of. So if anyone ever tells you they are the same...send them to this thread.

Shiny on left is BBC and dull on right is SBC. There is almost exactly 1/2 inch difference in the two. This half inch sitting lower in the frame and sagging rubber mounts have been the problem the entire time.

Mike

[esbstuff]

I believe you are wrong... The difference is 4x2, vs 4x4. You may check if you can verify...

[Mr.Chevy4x4]

Nope, these both came from 2wd trucks, and I'm positive they were original to both trucks. Of course one was 1/2 ton and one was 3/4.

Mike

[chengny]

There were differences in engine mounting components across the board.

Which engine mount/engine brackets (clam shells - shown above in the OP) were used, was dependent on the drive train configuration (2/4 WD), the engine group (L6/SB/BB/Diesel) and, in the case of the C/R series the GVWR (10 or 20/30) also mattered.

And it wasn't just the clam shells that differed. The frame/engine mounts and the engine mounts also were all specifically designed for the particular engine group and whether the application was 2/4 WD.

85 -91 C/R (1,2,3):



85-91 K/V (1,2,3):

[bigblock73]

I went 350 to 454 in my 73, ran the same engine side mount shells...new rubber mounts...fit like a glove, even cleared the headers with no mods. I have always been perplexed by the differences between mounts, engine and frames...guess I got lucky.

[cheepin]

Originally Posted by bigblock73

I went 350 to 454 in my 73, ran the same engine side mount shells...new rubber mounts...fit like a glove, even cleared the headers with no mods. I have always been perplexed by the differences between mounts, engine and frames...guess I got lucky.

I swapped a 454 into a 79 suburban, that had a 400. I used the 400 mounts. everything bolted up and aftermarket long tube headers fit. The only issue I had was fuel pump. Had to find a short bowl for a 454. I think I used one from a 70 Malibu with a 454.

[bigblock73]

I ran a Holley mechanical pump...more than enough clearance there.

[KQQL IT]

I believe a 73 is back more than a 74 as well, to make room for the HEI...

I kept notching and massaging my motor mounts, my distributor against the fire wall.

[68post]

How many of these are available new ?

I hope to eventually be doing a sbc to bbc swap on a '79 K30 and will want to buy new engine mounts for sure, but will buy the frame mounts also if it helps the swap.

Rubber mounts - new , and clamshell frame mounts - used only ???