Exhaust Manifold Bolts , Big Block

[nuch_ss396]

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Based on what I've seen,most 1969-70 Big Blocks including trucks,came with a longer shouldered bolt on the exhaust port end holes,(bolt #3909830 3/8 X 16 X 2&1/16)..and a shorter non-shouldered non-washered bolt on the inside holes,(bolt #3909821 3/8 X 16 X 1&3/16).
Also remember that what GM recommended an engine assembler to install vs. what that assembler actually did install,were not always the same thing.

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I've heard this from some of the Corvette guys as well.

Nuch