i've tried two diffrent compression ratio calculator using ctr pistons in a gsr block/head and they both came out to be over 13:1. does that sound right? i always thought it was less the 12:1. i've heard of so many people doing this or wanting to do it - i'm just wondering - is this safe on regular pump gas? (90ish octane)

 

Are you sure you are doing it right? Here is what i came up with using the cspeed calc.

CR: 12.042422511586593

Displacement: 1797.5627647736114

 

i used all the right parts for the calculations. the only thing i'm not sure with is the heard gasket. i guess i was going with the 1 layer. now with the 3 layer(oem), it comes out to 12.4:1. thats a little closer but still a bit high.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sinister357 &raquo;</TD></TR><TR><TD CLASS="quote">now with the 3 layer(oem), it comes out to 12.4:1. thats a little closer but still a bit high.</TD></TR></TABLE>

The C/R with PCT slugs in an otherwise stock B18C1 is going to be quite high. Low to mid 12's is an accurate estimate.