My 383 can handle 21 degrees of timing at WOT and 10lbs boost on 91. I'm running the same plugs and the same gap. My cam has similar specs aside from LSA. You might have an intake leak. Do a hard run, shut it off and then pull your plugs and have a look at them all.

It would be good to know what AFR he was doing the runs at.

Also, what did you use to figure out compression?

 

Ok. What is the intake centerline so we know how much advance its got? Even though its not guaranteed to be exactly at that unless the cam is degreed in when installed.

 

forgot @.595 on exhaust. cant find my cam card at the moment so i called texas speed. they dont show any advance so he said its most likely at 112.

 

I talked to texas speed and they gave me my guestimated cr.

 

I don't know how much your pistons come out of the hole but assuming 0.010 and using the specs above, I calculate 12.4:1 static compression ratio. With all things the same, a 72cc chambered head will bring you down to 11.1:1. Like has already been said, DCR is more important than SCR. I would need the ICA of your cam (should be on the card) to throw in the equation to calculate your DCA.

 

well **** if i am at 12.5 i cant run pump gas can i? i think it may need to have the heads pulled and thicker head gaskets in.

 

what if i switched to a .060 head gasket?

 

with a 4cc piston .060 head gasket 63cc heads i calculate 11.7:1. so change the head gasket or run race gas i guess is the question.

 

ok so i found that cometic makes a .066 compressed head gasket. so that would get me to 11.6:1 compression. my question is will that thick head gasket cause me problems later down the road?

 

You said you had flat top pistons in the first post... Are you running flat tops or flat tops with valve reliefs, or dome pistons?

BTW, quench is a pretty important step in building an engine. If you throw thick head gaskets on there, it will be more prone to detonation.