93 LT1 396 going w/ a AT1 D1 or D1SC 12psi max. Desired CR 8.5:1 or 9.1 w/ the piston? Cam choice 233/242 .569/.576 115 LSA. Main area of concern is I don't know the CC on the heads and they were milled 10/1000th. So would it be wise to just go 8.5:1 to be on the safe side?

LT1 heads are 2.00/1.56
Flow chart reads w/ a 190 port volume
Int / Exh
136 132.7
182.4 159
202.3 162.5
220.6 169.2
237.2 175.8
263.7 189.1
270.4 194.1

Could I still use my 918 springs the above cam w/ out a problem? What kind of numbers could I expect to see? Thanks for any input or advice.

 

Stk LT1 heads are 54cc. My heads were milled 10/1000th and have 190 port volume. 2.00/1.56 for valves

Since I don't know the CC on my heads what is a safe CR to go w/ for a boosted application? I want 9.1 but it may be higher since I don't know the CC on the head so to be safe would 8.5:1 be the smartest choice to go with?

Thanks.

 

Yes the stock LT1 chambers run around 54cc. For a 23 degree type sbc head a rule of thumb is that every 0.007" straight milled equals 1 cc. So your chamber now should measure around 53cc.
If you know your deck height, gasket thickness and desired CR you should be able to calculate piston dish volume.

 

Thanks SSS! Deck height is zero. Shooting for a .039 head gasket but may go .040 instead since I don't know the height after it being compressed.

 

That calls for a big piston dish something between 25-30 cc for a target CR of 9-9.5.
There is a CR calculator as well some other usfull calculators here:
http://www.camaroz28.com/calcs/index.shtml

 

Ross pistons just said the same thing. For 9.1cr about a -30cc. Thanks for the help.

 

I thought stock chambers were 58 cc?

 

NM. I don't know where I got 58cc but I always thought that for some reason. Hmm, learn something new everyday.

 

I'm pretty sure the LT1 head is 58cc and the LT4 head is 54CC. Either way you will need about -30 dished pistons.

 

Stock LT4 heads are 54 cc. Stock LT1 heads are 58 cc heads. I figure with your heads milled that much you have between a 56-57 cc combustion chamber now.

 

Thank you METALBEAST. I've decided a -31cc piston and .039 gasket. Gives me a little room to play with.