how does gm come up with a stock vortec motor having 9.4 cr. having 12cc dished pistion with them .025 in the hole? , 64cc vortec heads, .045 head gasket how does that come up to 9.4 cr? i did the math and come up with around 8.9 cr. so what am i missing here?

 

I have read that Vortec heads are more like 61cc. Still not 9.4. By the way my wifes aunt lives in Taccoa. Beautiful place.

 

Vortec heads are 64cc heads. I dont know where you get 91 cc, even the old 70s smogger heads only had 76cc chambers. Do you mean 9.1 scr?

 

Where do you get a 12cc dish? Every GM-built OE Vortec headed 350 I've seen had flat top pistons in it, which is typically a 5cc or 6cc "dish", not 12cc.

 

well that what they come was dish piston just like the l98. and the heads are off it now

 

I'm sorry for the typo, I mean 61 cc. I have seen that when you cc them they come up 61 instead of the advertised 64 cc. Not going to make a great difference.

 

anyone have any idea?

 

I think it's a typo. The r code 350 I put in my car had dished pistons when i pulled it apart..... no way it was over 9:1. The heads are 64cc's stock. Just figure the compression up on paper for whatever you're working on. It is more accurate then advertisments. Here is a pic to show it is dished. I've only rebuilt the one r code though, but everything was as it came from the factory.

 

they have alot of typo about it. even somewhere i read it was talking about gm uping the cr in 96 form 8.9 to 9.4.