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y5e06 11-08-2009 07:55 AM

BBC vs SBC mount locations & dimensions?
I'm looking for specifc info in regards to BBC vs SBC mounting locations.
From what i've read, the engine/frame mounts are interchangeable in as much as BBC engine will fit on the SBC mounts & vice versa.
So, Are the dimensions from the motor mount boses to the rear of the block the same for SBC & BBC? If I swap from a BBC to SBC, using the original mounts and keeping my current TH400 trans, will I have to relocate the trans any? Are the block dimensions the same for these two reference points?


Bryan59EC 11-09-2009 07:31 PM

In a lot of cases--they interchange without issues.

early Chevelles----will bolt up (with the exception of the 307 Frame mounts), but the big block will sit higher than it is supposed to on SBC mounts.

I believe the 73-87 Chev/GMC trucks require a different frame mount as well, but the clamshell is the same.

58-64 Chev full size----a BBC will bolt up on the factory v-8 mounts, but not the 6cyl mounts.

Might help if we knew what you were working on.

y5e06 11-09-2009 09:38 PM

ah, yeah. thanks
454 '86 suburban

Bryan59EC 11-10-2009 06:21 PM

The 454 rubber mounts were different on my 79 from a SBC to a BBC
The rubber mounts are the ones that bolt to the frame-----both sets of holes should be in the frame for these.

You will need to change the exhaust to meet up with the BB.

You will need a LARGE radiator (454 trucks got a 4-row), The BB fan shroud, and fan.

Wiring to the front of the motor may need to be lengthend----I was about 2" short for my alternator wiring.

A 454 Flywheel or Flexplate must be used.

Very straight swap with no issues at all-------did mine in an afternoon, and had the exhaust put in the next day (of course I was much younger and had more energy way back then).

denunger 11-10-2009 07:22 PM

bbc mount
I have dropped bbc in sbc mounts in suburbans/pickups9'73-'87) several times without any problem. I know there are different mounts for big blocks, but????

6426yy 11-17-2009 07:09 AM

I just put a BB in my '83 without changing the mounts. At one time I thought it wouldn't work but I decided to try and voila!

y5e06 11-17-2009 09:33 AM

did the engine position change any between the SBC & BBC when reusing stock mounts?

edit: never mind. that question doesn't make sense since located the same w/ reusing the same mounts!

richard stewart 3rd 11-17-2009 11:10 AM

Here are some popular engine dimensions for swapping.

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