kazino42

I acquire this from a trade and had no spec sheet. The guy said it was CP standard 87mm 10:1. I have not build an H22, normally B-series dome pistons are around 10:1-11:1. It looks domed and higher compression. Block is sleeved, oringed and should I get a thicker head gasket to lower the compression?




Modified by kazino42 at 6:29 AM 5/20/2005

_entropy

JE's 10:1 H22A pistons have a 1.3CC dome. I'm not an expert on guessing piston sizes from pictures, but that looks pretty close. Call up CP and see what they can do for you. I'd go for a set of lower compression pistons.

Oyvind Ryeng

What is the compression height (centre of bolt to the top of the outer edge of the piston) and what is the dome volume? Knowing these two you'll get alot closer to finding the compression. Compression ratio = (Volume with piston @ BDC)/(Volume with piston @ TDC)

_entropy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Oyvind Ryeng &raquo;</TD></TR><TR><TD CLASS="quote">What is the compression height (centre of bolt to the top of the outer edge of the piston) and what is the dome volume? Knowing these two you'll get alot closer to finding the compression. Compression ratio = (Volume with piston @ BDC)/(Volume with piston @ TDC)</TD></TR></TABLE>

CP doesn't list dome/dish volume, and I'm guessing this guy probably doesn't have any way of measuring that.

kazino42

I don's have the spec sheet. Tried searching for pix, to get an idea what compression it might be. I looked at the stock pistons and they are domed a little bit and looks close to it. I'm hoping it's no more than 10:1, don't want to buy new pistons. Would rather get a thick gasket to lower the compression to 9.5:1.

g2turbo

email a pic of that piston to Darius at CP pistons he should be able to help you out. His email is available on their website.

PrettyLude

take a better picture of it standing straight up,

kazino42

Here's a another picture. Did alot of searching for other type's of piston and looks close to a 10:1 compression. Found out that the head has a 53.8cc chamber.

PrettyLude

it looks like it would be more than 10 to 1, cuz 10 to 1 is normally flush with the piston

earl

They are the 10-1's
The 11.5-1's have a +10.4 dome volume and from the pix, your domes are nowhere that big.

kazino42

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by earl &raquo;</TD></TR><TR><TD CLASS="quote">They are the 10-1's
The 11.5-1's have a +10.4 dome volume and from the pix, your domes are nowhere that big.</TD></TR></TABLE>

Thanks, Earl. I wasn't really sure about it. I'm so use to seeing B-series piston with dome are higher compression. But, I notice the head on the H-series has bigger combustion chamber which will yield a lower compression.

Anyone think, it would be O.K. to stay 10:1 for boost or get a thicker head gasket to drop it 9.5:1? I really prefer to use OEM head gasket, but would like to get a lower compression. Maybe go with Cometics?

PrettyLude

oem gasket will be fine

earl

You can keep the 10-1 with low boost (5-7 lbs) and a soft tune on the street. If you are going for higher boost and power, you might want to lower the c/r number