Engine Compresion
Thread Starter
|
Elder User
Joined: May 2003
Posts: 575
Likes: 0
From: Orlando, FL
Engine Compresion
Don't know what happened to the post I put up this afternoon about the same thing, just disappeared. Anyways, how can you check the compression of each cylinder and the overall compression ratio of the engine overall.
Posting Guru
Joined: Sep 2002
Posts: 2,195
Likes: 1
From: San Antonio, Texas
You use a compression gauge. You pull 1 spark plug at a time, and the gauge hose threads into the the hole, then crank over the engine about 3-5 revolutions (make sure you pull the coil wire so the engine doesent start up) and watch what it goes up to, also watch it for a sec to see if it leaks down, that not good if it does.
You do this for all 8 or just 4 on 1 bank if your seeing if your timing chain jumped.
I think the compression should be at least 70% of the rest.
I could explain alot faster in person, but you know.
You do this for all 8 or just 4 on 1 bank if your seeing if your timing chain jumped.
I think the compression should be at least 70% of the rest.
I could explain alot faster in person, but you know.
Fleet Mechanic
Joined: Sep 2003
Posts: 1,716
Likes: 15
I was taught long ago to pull ALL of the plugs, and block the throttle open.
And use a screw-in type of compression tester. The rubber nose kind of ones are a waste. If they are still around anymore.
I test each cylinder 3 times, hitting the pressure release button between each test, of course. A decent gauge holds pressure, it is a peak-reading gauge. So there is a pressure release to reset the gauge for the next reading.
And use a screw-in type of compression tester. The rubber nose kind of ones are a waste. If they are still around anymore.
I test each cylinder 3 times, hitting the pressure release button between each test, of course. A decent gauge holds pressure, it is a peak-reading gauge. So there is a pressure release to reset the gauge for the next reading.
Last edited by Torky2; Nov 13, 2003 at 09:04 AM.
Posting Guru
Joined: Sep 2002
Posts: 2,195
Likes: 1
From: San Antonio, Texas
Yea, you should pull all the plugs, I was just giving a basic layout.
And those rubber nose types are kinda junky, I like the screw in type best, they are the most accurate. And, you do check at least 3 times.
And those rubber nose types are kinda junky, I like the screw in type best, they are the most accurate. And, you do check at least 3 times.
Postmaster
Joined: Jun 2001
Posts: 4,496
Likes: 0
YOu can't check for the overall compression ratio with the heads on. A Compression gauge will show different readings there isn't really a dead on relationship to compression ratio and cylinder (psi) compression. If everything is stock you can roughly guesstimate it will fall in the 8:1-8.5:1 ratio +/-. It could potentially be a lot more or less because every head casting will differ slightly so variences in cc are realistic. You have to take the head off figure piston cc, piston to deck clearance, compressed gasket cc, cylinder head cc. Sounds like a lot but really isn't that bad. Good luck
