Bolt Torque?

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Dec 17, 2025 | 10:04 AM

mbp

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Bolt Torque?

Hello. Can anyone tell the torque on the 3/8" bolt that attaches the bell housing to the block? I can't seem to find it in the A.I.M..It's on a 1969 4 speed if that makes any difference. Thanks in advance.

Dec 17, 2025 | 10:28 AM

ctmccloskey

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Some say 30 foot pounds and many say 37 foot pounds of torque to secure the 3/8" bolts to the bell-housing on a C3 Corvette.

Dec 17, 2025 | 01:02 PM

427Hotrod

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Two ugga duggas.....

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Dec 17, 2025 | 02:54 PM

bashcraft

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Quote:

Originally Posted by 427Hotrod

Two ugga duggas.....

JIM

I've never used a torque wrench on bell housing bolts, nor have I ever heard of anyone using a torque wrench on them.

Dec 17, 2025 | 03:26 PM

Rebelyell

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Suggest a few simple straight-forward precautions:
Before you put any real force on BH bolts
Ensure faces of both block and BH are very clean
Chase threads in block's face, and Ensure BH is firmly seated to face of block, all around.

Dec 18, 2025 | 08:19 AM

redwingvette

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Tighten till it breaks and back it off a 1/4 turn LOL

Dec 18, 2025 | 09:44 AM

Wally8

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When you can't find a torque in a maintenance manual you should look up standard torque which depends on bolt size, thread and grade and if you're using lubricant. Here it is for 3/8".

Typical Torque Values (3/8"-16 UNC)

SAE Grade 2: Around 15-25 ft-lbs (dry).
SAE Grade 5: Approximately 23 ft-lbs (dry).
SAE Grade 8: About 33 ft-lbs (dry).

What you're putting the bolt in to matters as well since you may not torque to a spec if it's in aluminum or something like that. Example being rocker studs in an aluminum head.

Wally

Dec 18, 2025 | 02:54 PM

carriljc

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mbp
One of my Manuals say 30 ft-lbs and the other says 40-50 ft-lbs.
I believe that last time i did mine I went to 35 ft-lbs with blue locktite..... so I'd recommend that.
And, YES, I use torque wrenches.

Quote:

Originally Posted by mbp