drunknbass

doesnt anyone know what cp pistons piston to deck height is?. cause im trying to figure out my cr so i know what thickness head gasket to use.
im using the c-speed calculator but it seems really high

TOM J

Do you have your piston job sheet?
I might be able to help you out

drunknbass

SIXTYdashONE

drunknbass

my setup is pr3 head
b20 block 84mm with 89,mm stroke (stoke bore/stroke)
the guy i bought to pistons from said they have a 2 cc dome
and my head is milled .030
so accoring to the http://www.c-speedracing.com/h...c.php
cr calc my cr with a oem headgasket is @ 12 and with single layer its 12:7 ish
and thats me factoring the milled head into the piston to deck height feild by setting it to 0
i dont know it putting it in that feild is really calculating the cr right. and if cp pistons have a 0 piston to deck height id need to factor that it also. so if thats true id need to put a -.03 in the piston to deck height field right? (that field is negitive by default so thats why id put -.03 instead of .03)

TOM J

For example if you use a ls combo ls rod ls crank it would be .0013 in the hole if the block was not milled. so if the block is milled it will change.


Modified by TOM J at 3:32 AM 8/20/2004

743power

.029", assuming the b20 has a .030" PTD height and 1.180compression height, like the b18a/b

TOM J

If you are looking for comp with you set up it looks to me it would be 12.43 to 1 with a 2cc dome. This is how I got the info.
You have a b16 head 42.7cc B20block 8.340 height a stroke of 3.504 B20/LS B20/LS rods and a pin height of 1.181 which is .0013 in the hole. I took the gasket and devided it by 3 since you are using just one layer so that would give us .008.4 thick and .0030 off the head I came up with 12.43 comp

I hope this is what you are looking for It is late here at the shop and my math may be off but this should be dam close

drunknbass

ok cool.. cause when i was calculationg it on the thing myself it was coming out as a high 12 with single layer.. i was hoping for something closer to 12:1 so thats why i was trying to get a better judgemtn of the cr. cause its a weekend car running 95 octane minimum . i dont want to make it too high.
also these pistons are setup to run oem b20 piston rings. so should i gap them to oem specs?
and how do i measure the piston wall clearance?.
this is my first buildup so thats why i have alot of ?'s

TOM J

On there stuff I am not sure where they measure from but if you make the bore 3.307 it looks like you will have .003 thou clearance that should be ok. Keep inmind that is what I seen on there spec sheet. I would not gap the rings more than .005 thou per inch of bore so you would take your bore 3.307 and x it by .005

drunknbass

i came up with close to .016
so should i gap the 1st ring .016 and the 2nd (middle) .018 ?

drunknbass

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TOM J &raquo;</TD></TR><TR><TD CLASS="quote">On there stuff I am not sure where they measure from but if you make the bore 3.307 it looks like you will have .003 thou clearance that should be ok. Keep inmind that is what I seen on there spec sheet. I would not gap the rings more than .005 thou per inch of bore so you would take your bore 3.307 and x it by .005 </TD></TR></TABLE>
3.307 is 84mm
so that means i cant hone at all or the clearances will be too loose?
what if i just run a flex hone through to clean it up alittle.. if i just make a few quick passes will that take out too much?

TOM J

If you do a quick hone you should be ok

drunknbass

cool thanks.

TOM J

Anything we can do to help.


Tom Jung