I have a 350 TPI with the stock 083 heads... they have been machined for screw in studs and guideplates, however the valve guides have not been taken down any. I am running a GMPP zz4 cam, and I was wondering if I should go with 1.5, 1.6 or a mix? If a mix, use 1.6 on intake or exhaust?

Thanks.

 

Just my two cents worth. Those heads are probably flowing about all they can now with that cam, adding a bit of extra lift probably won't give any more flow or power. And I'd say you're at about the point the guides will hit the retainers now anyway. On my car with Felpro seals the stock cam put the retainers right on the top of the seals. Not much extra clearance there.

 

Oh, I forgot to mention, the heads have been really worked over both in the port and in the bowl. Also, the motor was mocked up with a low tension spring and retainer to guide clearance checked and was good, without the head gasket. I figure I should be safe with 1.6 by the time I get the gasket on. I dont know though, think I should play it safe and stick with my 1.5s?

 

If you mix the ratio's I have always read about people going 1.5 on the intake and 1.6 on the exhaust.