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Small Block vs. Big Block frame mounts

mattrains

mattrains

MRAINS
Joined
Dec 10, 2011
Posts
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Location
Atlanta, Ga
Is there a difference in the mounts that bolt to the game between a big block and small block motor. Here are pictures of what came off of mine. I'm coming from a big block going to a small block and need to know if I should be looking for new mounts.

And I'm not talking about the clamshell mounts. The mounts that bolt to the frame.

yzu4ypu6.jpg


abyhy6u7.jpg
 
Trucks that came originally with BBC's have different mounts. The holes are different. Where SBC's and BBC's use 3 bolts to fasten the rubber motor mount, the other size motor has holes opposite of the other.

I have the mounts in the shop for both sizes. Will take a pic and show them later.
 
Even the rubbber mount is different between the two sizes of motors.
 
I guess it depends on who you ask....I've re-used the SB mounts when I put 454's in my GM trucks (73-87),I know the holes the mounts bolt into in the crossmember are different location for the big blocks,they are already drilled in the member--but I never noticed any difference in the rubber mount itself,and there was no "other" listing in a Doam motor mount catalog for big block VS small blocks back when I was doing swaps anyway..the clam shells that bolt to the block are different on 4x4s ,they have the thru bolt hole about 1" higher than ones used on car and 2wd truck engines...using the wrong ones will put the oil pan right against the crossmember or might not work at all on some years..
 
I've swapped a bunch of SBC to BBC, and not once have I changed the rubber or anything else. Car to truck clam shells are different, but 2wd to 4wd, SB or BB are the same. My car never came with a big block, I didn't do a thing to put the 454 in.
 
I think most all GM cars & trucks used the same motor mount for a decade or so...

I too, have dropped 454's right onto the mounts after taking a 350 or other SB out too,(after swapping the original engine clamshell brackets to the BBC) --it wasn't until I bought of all things,a Chiltons manual for both K5's and another for pickups and they showed the locations to bolt the mounts into the crossmember using the "other" set of holes,being slightly different for a SB vs BBC...(and six bangers used another set of holes)....its so "close" that with used mounts with some wear in the center hole,that the thru bolts will go thru anyway,slightly hard perhaps..
 
I forgot to snap pics of the steel mounts. :doah:
 
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