94 883/1200 Compression High??
Thread Starter
|
6th Gear
Joined: May 2006
Posts: 11
Likes: 0
94 883/1200 Compression High??
Hello,
I have blown a few head gaskets over the last few years and I would really like to find out what is causing this. I have a '94 Sportster that was converted from 883cc's to 1200cc's by a previous owner. I just got the rear cylinder back together and ran a compression test. Here are the findings:
Front = 165psi
Rear = 170psi
Any idea what compression ratio I have based on these numbers?
Thanks for the help. Great forums here.
I have blown a few head gaskets over the last few years and I would really like to find out what is causing this. I have a '94 Sportster that was converted from 883cc's to 1200cc's by a previous owner. I just got the rear cylinder back together and ran a compression test. Here are the findings:
Front = 165psi
Rear = 170psi
Any idea what compression ratio I have based on these numbers?
Thanks for the help. Great forums here.
Road Warrior
Joined: Dec 2005
Posts: 1,950
Likes: 2
From: Colorado Springs, CO
RE: 94 883/1200 Compression High??
Cylinder pressure is a function of rod length, stroke, static compression, cam timing, atmospheric pressure, and a couple other things. Without knowing all that you can't tell what your static compression is. The RBR Racing web site has a nifty calculater to help you figure it out.
However, that won't help you. The only important number you need to know is the effective (dynamic) cylinder pressure, which you already know is 165 and 170 psi. That's about what a stock twin cam engine is at sea level is. So compression or cylinder pressure is not your problem.
You'll need to take things apart to find the answer. Check for flatness of the head surface and the cylinder top. I would install new high quality head studs and bolts, and Helicoil the cases. That will make sure your clamping force does not change.
However, that won't help you. The only important number you need to know is the effective (dynamic) cylinder pressure, which you already know is 165 and 170 psi. That's about what a stock twin cam engine is at sea level is. So compression or cylinder pressure is not your problem.
You'll need to take things apart to find the answer. Check for flatness of the head surface and the cylinder top. I would install new high quality head studs and bolts, and Helicoil the cases. That will make sure your clamping force does not change.
Thread
Thread Starter
Forum
Replies
Last Post
trickassfoo
Sportster Models
3
Jun 22, 2013 06:08 PM
