oldgold49er

We were about to install the heads when I noticed the difference in the gaskets. See pix. There is an additional hole in the old gasket. Both the heads and the block have a water port. If I install the new gasket, I would be blocking the flow. Thanks. The gasket set is Felpro # HS 8180 PT5

Also got rid of the plastic single roller and installed a double roller setup.

Avispa

The Fel Pro gaskets in your picture will work. I'm using them on my L72. The upper opening to the water jacket in the block will provide enough coolant flow.

You may want to check the piston height with respect to the block deck. They vary, and if you never had the block decked, chances are the piston quench surfaces are "in the hole", or below deck level by a few thousandths, sometimes as much as .030". The gaskets in your picture should have a compressed thickness of .039". Recommended quench clearance (distance from piston flat surface to head flat surface is about .040" to .044" (.039" will work just fine).

Depending on your piston measurements, you may need a different thickness gasket. My block has been decked and the pistons are .017" out of the hole. I have to run a .025" copper shim to have enough quench clearance.

oldgold49er

Thanks for the advice.
The block still has the original horizontal machining marks. it is also still std. bore. Pistons/unground crank original GM. I have not yet been able to determine the cam. Numbers do not seem to indicate GM cam.
Would it be a good idea to punch out the new gasket in this area to improve the flow?
I will make the piston/block measurements anyway. Much easier now!! Thanks again for your help.

Avispa

I think I'd leave the gaskets alone. You'll get plenty of water flow from the existing hole. I don't like to cut gaskets that are exposed to very high pressure like head gaskets; you never know what a rough edge will do to the sealing surface.

A GM L72 cam should have the number 3143 stamped on the back face of the rear cam bearing journal (for the cam part number 3863143)

JohnZ

It will also have "3144" (for 3863144, the casting number) in raised characters on the core casting between a journal and lobes.