I am looking for a 63-64 dual exhaust LH exhaust manifold for a63 starfire. I think the part number is 587793LH. The previous owner changed heads some time ago, and used heads with single exhaust type manifolds. I want to go back to original duals.

 

The heads have nothing to do with single or dual exhaust. It is determined by the exhaust manifolds whether the car had single or dual exhaust. Possibly your car did not have dual exhaust from factory.

 

He has a 63 Starfire. I think his point is that a P.O. changed the heads and converted to single exhaust, likely in an attempt to increase gas mileage during the dark days of the mid-70s.

 

An ill-advised attempt at that. Aren't duals usually viewed as being an aid to gas mileage?

 

I didn't say it was an intelligent attempt...

C'mon, you read the interwebs. About 80% of the responses to technical questions are completely wrong.

 

Still has nothing to with the PO changing the heads to install single exhaust. Single exhaust could have been installed with the original heads still in place.

 

I'm not buying changing heads for fuel mileage or to reduce detonation. Then, as until the end of V8 production, Oldsmobile changed compression with pistons, not cylinder heads. Granted some heads had bigger combustion chambers than others but all 62-64 394 heads were identical.

1963-1964 394 pistons from 1964 CSM:



More likely the original LH manifold was damaged, a replacement couldn't be found, and the car was changed to single exhaust. That or the car had a cheap owner who was trying to get away from the expense of replacing dual exhaust.

Engine ID location and charts:



If the heads were in fact changed, look at the engine ID number above the center exhaust port on the DRIVER SIDE head. If the heads are original to the car, there will be a "J" prefix (4bbl engine) with a "S" suffix (Starfire engine) after the engine ID number. If the number is on the passenger head, heads have been off the car and reversed. If head has any other prefix and suffix combination, the heads or possibly the whole engine has been replaced.

I guess there's a remote possibility the heads were pulled and reconditioned, and a thick head gasket was installed to drop compression some to tolerate low octane fuel. But changing heads? That premise doesn't hold water.

 

Grp 3.601 p/n 587793 is the 394 LH dual exhaust manifold.

 

Thank you for your responses! I can assure you that the car came with duals. It belonged to my uncle and was bought new at Tichenor Chevrolet in Hartford, Ky. I borrowed it for the prom in 1966. I can only guess at the reason why it was changed. I saw and heard those pipes with my own faculties, and they sounded nice!