Exhaust Manifold Bolts , Big Block

[Mr70]

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.

[nuch_ss396]

[ QUOTE ]
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.

[/ QUOTE ]

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

Nuch

[Woj]

I agree with what Rick (mr70) said. My car is unrestored (69 SS Chevelle) and when I removed the exhaust manifolds, the non-shouldered bolts were on the inboard ports and the shouldered on the outboard ports. I tried to put the shouldered ones in the inboards and they would not seat. The holes are not deep enough, at least on the heads on my car. The repops that are available today don't match what came on my car.

Hope this helps.

Phil Woj

[nuch_ss396]

[ QUOTE ]
I agree with what Rick (mr70) said. My car is unrestored (69 SS Chevelle) and when I removed the exhaust manifolds, the non-shouldered bolts were on the inboard ports and the shouldered on the outboard ports. I tried to put the shouldered ones in the inboards and they would not seat. The holes are not deep enough, at least on the heads on my car. The repops that are available today don't match what came on my car.

Hope this helps.

Phil Woj

[/ QUOTE ]

Phil,

Ok - there are eight bolts per side. If you numbered them
from one to eight ( L to R ), which bolts were of the shouldered type.

Nuch

[1969grb]

Nuch, Shouldered bolts would be 1,2,7,8 non-shouldered would be 3,4,5,6 Grady

[bluel78]

Did the aluminum heads use the same bolts?

[nuch_ss396]

That's a great question on the L/89 application

Nuch

[Woj]

Nuch,

Grady has answered the numbering question.

As I recall, the ears on the exhaust manifold are are of different thickness by about 1/16". The inboard ears are about 1/16" thicker than the outboard ears.

Phil Woj.