Technical question..6.5 gasket

[Rod@Night]

I have an 84 6.2 J engine. Replacing head gaskets . Had the heads milled but only took off .05 There is a 1/10 over head gasket set available for the 6.2. I am concerned about 2 things first the boar on the 6.2 is 3.9764...the boar on the 6.5 is 4.055. Putting the larger diameter head gasket on the 6.2 seems like one might be asking for trouble. Second is the only reason for the 1/10th thicker gasket to accomidate valve clearance if one has had the head milled down? ...I dont know if the heads have previously been milled down or not. A thicker gasket is not offered for the 6.5.
One of the gaskets I took off looked more metallic and had a waffle like pattern. The other gasket was more steel like and had the light orange silicone beads around the water ports. So what head gaskets should I put on. I'd hate to put on a 6.5 gasket and bump the valve top into the piston...Best regards

[john8662]

Actually Fel-pro does offer a thicker head gasket to account for milling of the heads. It sounds like you need the thicker gaskets. Usually there are two options, either you use the thicker gaskets, or the valves have to be adjusted in the heads, ground into the heads more like for clearance. The gaskets that are metallic are likely the factory gaskets, I couldn't make out a brand on a set that I took off like that. The gaskets that have the orange barriers around all the sealing areas are fel-pro, I don't know if the current gaskets from fel-pro look like that or not. Those look to be good gaskets in my opinion (the orange ones).

To consider the 6.5L gaskets you have to know what year model heads you have, there is a port on most 6.2L heads that isn't on the gasket for the 6.5, and it will cause problems if this port is in the casting on your heads. Take a look here for that info:

http://www.thedieselpage.com/members/gmheads.htm

I would check with the machine shop that worked on your heads and ask them about how close the valves are in the heads now that they have been milled, and if any adjustment has been made to the valves.

[odee]

I have a set of the thicker felpro gaskets ordered for my 6.5 built up. Has anyone on the board got any experince with these gaskets? I talked with the felpro rep about them, he seemed to think the gaskets would be fine. I plan on putting a turbo on this engine also.