VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Manifold Hex Bolt

On a 1946 Chevrolet 216, what is the HEX BOLT SIZE/LENGTH of the SIX BOLTS that bolt both the exhaust manifold and intake manifold into the HEAD. Both SAE and METRIC information is appreciated. Planning on using Grade 8 or higher.

I already have the info on the two end STUDS.

The best I can tell the parts book lists the stud as: 3/8-16-13/4. The blowup of the engine shows the bolt to be in group 8.900. There is a caddiam bolt listed there:3/8-16x13/4.

If your manifold and head are smooth or have been planed then there is not as much need to crush the hell outa the gaskets by going to overkill with stronger bolts than what the factory used. Just saying.

The above is the best I can tell you from the parts book.

What is the matter with your old bolts and studs?

Best,

Charlie

Replacing exhaust manifold due to non working heat riser valve. Replacement manifold is exact same GM casting number, but with a fully functional heat riser valve. Replacement has also go thru ceramic coating in cast iron gray.

In the procedure for replacement, I am replacing ALL gaskets and manifold to head bolts and manifold to exhaust pipe studs.

The truck is currently in running, drivable condition, just trying to gather all the parts needed to make the swap in advance. I did not want to pull a hex bolt just to get the size, if the information was available otherwise.

Thanks for the info Charlie. Will proceed with 3/8-16 1 3/4 grade 8 hex bolt.
Randy

I recommend that you use studs and nuts to mount the exhaust manifold. It will make the job a lot easier.

Plus the studs will not tend to loosen as much in the head as bolts. The advantage of a stud is that the threads between the stud and head are only in tension. There is very little torque on those threads.

Gene…where are you?

At home,,,,,,,,,

The factory used studs at the end and bolts for the remainder. I have never had a problem with that method.

I would use the factory bolts with no markings if possible.

Gene,
I am wanting to keep everything as original as possible…no studs except on the ends.
Can you answer the LENGTH of the SIX INTERIOR 3/8-16 bolts?
Please and thank you!
Randy

The parts book does not list the bolts as to size because they are ordinary hardware.

There is 2 different length bolts used, the 2 bolts adjacent to the outer studs having a very think round washer measure 1 1/8” under the head.

The other 4 bolts use the heavy pressed steel plate, and measure 1 3/8”. Under the head,
These are original bolts on an original 1939 engine.

Thanks to ALL, for the responses.
Randy