Big Block Exaust Manifold Jam Bolts

[Rich P.]

I know that the big blocks stopped using the french locks for the exaust manifolds in 68 because of the smog tubes. But when did they start using the special shallow thread jamb bolts where the french locks would have been? Here is a few pictures of some.

Thanks in advance for your help,

Rich

[Joe L.]

Re: Big Block Exaust Manifold Jam Bolts

I know that the big blocks stopped using the french locks for the exaust manifolds in 68 because of the smog tubes. But when did they start using the special shallow thread jamb bolts where the french locks would have been? Here is a few pictures of some.

Thanks in advance for your help,

Rich

Rich------


If by "jamb bolts" you mean the special locking bolts, I believe that these bolts were first used sometime during the 1967 model year. The part number of the bolts, GM #3909821, is also consistent with that time period.

[Rich P.]

Re: Big Block Exaust Manifold Jam Bolts

Joe,

I wonder if they used them on the few 66 AIR cars also.

Rich

[Joe L.]

Re: Big Block Exaust Manifold Jam Bolts

Joe,

I wonder if they used them on the few 66 AIR cars also.

Rich

Rich-----


It's remotely possible, but I doubt it.