compresion ASAP please
Supreme Member
Joined: Oct 2000
Posts: 2,264
Likes: 0
stick a Vaccum Line Into the spark Plug Hole and And, while cranking the Motor Over, Suck On the Line.
The # of cranks it takes before you pass out Is your compression.
------------------
60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver
Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype
The # of cranks it takes before you pass out Is your compression.
------------------
60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver
Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype
Member
Joined: Oct 2000
Posts: 405
Likes: 0
From: Gulf Coast
Car: 1988 Trans Am GTA
Engine: 5.0 TPI
Transmission: TH700-R4
Axle/Gears: 3.27
I think a simple question deserves a simple answer.
Calculating Compression Ratio with a gauge is not a very accurate way of doing it. Most gauges have a rubber hose, this means that the air volume inside that hose (usually about 3-4 cc) is added to the combustion chamber volume during a measurement. The end result of his added volume is a reading that is 20 - 35 psi lower than the true reading. Besides indicating the added 2 cc of the threaded spark plug hole itself, these gauges are notorious for leaking as well.
Go to this page for information on how to calculate:
http://www.dragnbreath.com/dragnbrea...2HowtoFig.html
Calculating Compression Ratio with a gauge is not a very accurate way of doing it. Most gauges have a rubber hose, this means that the air volume inside that hose (usually about 3-4 cc) is added to the combustion chamber volume during a measurement. The end result of his added volume is a reading that is 20 - 35 psi lower than the true reading. Besides indicating the added 2 cc of the threaded spark plug hole itself, these gauges are notorious for leaking as well.
Go to this page for information on how to calculate:
http://www.dragnbreath.com/dragnbrea...2HowtoFig.html
Junior Member
Joined: Mar 2001
Posts: 20
Likes: 0
From: canada
Right. When you do the compression check, make sure all the spark plugs are removed and the injectors are disabled so fuel won't be getting squirted into the cylinders.
The readings between the highest and the lowest cylinders should not be greater than 10%. The closer they are to each other, the better.
Squirting oil into the cylinder(s) will cause the compression to increase some, but there should not be a dramatic increase.
When testing the compression, make sure that the very first pressure jump is close to the max pressure you get. That is, the pressure should not be low on the first crank and gradually increase with successive cranks.
Crank the engine at least 5 revolutions for each cylinder. If you get, for example 160 psi as a max reading after 5 cranks, the first crank should be well over 100.
A leak down tester is probably the best way, but using it calls for having a leakdown tester (two guage arrangement made by companies like Moroso, etc.) and an air compressor.
The actual maximum compression reading you get depends on a lot of variables - mileage, camshaft duration, rocker arm ratio, etc.
Post the numbers after you done the test with all the mods you've done to the engine (if any) and we'll try to help with the evaluation.
The readings between the highest and the lowest cylinders should not be greater than 10%. The closer they are to each other, the better.
Squirting oil into the cylinder(s) will cause the compression to increase some, but there should not be a dramatic increase.
When testing the compression, make sure that the very first pressure jump is close to the max pressure you get. That is, the pressure should not be low on the first crank and gradually increase with successive cranks.
Crank the engine at least 5 revolutions for each cylinder. If you get, for example 160 psi as a max reading after 5 cranks, the first crank should be well over 100.
A leak down tester is probably the best way, but using it calls for having a leakdown tester (two guage arrangement made by companies like Moroso, etc.) and an air compressor.
The actual maximum compression reading you get depends on a lot of variables - mileage, camshaft duration, rocker arm ratio, etc.
Post the numbers after you done the test with all the mods you've done to the engine (if any) and we'll try to help with the evaluation.
Supreme Member
Joined: Jul 2000
Posts: 1,014
Likes: 0
From: Kempner,TX,
Car: 1996 Vette / 1992 GSX1100F Suzuki
Engine: 1996 Corvette Coupe 388 LT1 (+.060)
Transmission: Auto
Axle/Gears: 3.07
<font face="Verdana, Arial" size="2">Originally posted by virtual:
Right. When you do the compression check, make sure all the spark plugs are removed and the injectors are disabled so fuel won't be getting squirted into the cylinders.
The readings between the highest and the lowest cylinders should not be greater than 10%. The closer they are to each other, the better.
Squirting oil into the cylinder(s) will cause the compression to increase some, but there should not be a dramatic increase.
When testing the compression, make sure that the very first pressure jump is close to the max pressure you get. That is, the pressure should not be low on the first crank and gradually increase with successive cranks.
Crank the engine at least 5 revolutions for each cylinder. If you get, for example 160 psi as a max reading after 5 cranks, the first crank should be well over 100.
A leak down tester is probably the best way, but using it calls for having a leakdown tester (two guage arrangement made by companies like Moroso, etc.) and an air compressor.
The actual maximum compression reading you get depends on a lot of variables - mileage, camshaft duration, rocker arm ratio, etc.
Post the numbers after you done the test with all the mods you've done to the engine (if any) and we'll try to help with the evaluation.
</font>
Right. When you do the compression check, make sure all the spark plugs are removed and the injectors are disabled so fuel won't be getting squirted into the cylinders.
The readings between the highest and the lowest cylinders should not be greater than 10%. The closer they are to each other, the better.
Squirting oil into the cylinder(s) will cause the compression to increase some, but there should not be a dramatic increase.
When testing the compression, make sure that the very first pressure jump is close to the max pressure you get. That is, the pressure should not be low on the first crank and gradually increase with successive cranks.
Crank the engine at least 5 revolutions for each cylinder. If you get, for example 160 psi as a max reading after 5 cranks, the first crank should be well over 100.
A leak down tester is probably the best way, but using it calls for having a leakdown tester (two guage arrangement made by companies like Moroso, etc.) and an air compressor.
The actual maximum compression reading you get depends on a lot of variables - mileage, camshaft duration, rocker arm ratio, etc.
Post the numbers after you done the test with all the mods you've done to the engine (if any) and we'll try to help with the evaluation.
</font>
Since I get "beat-up on" when I post one that's wrong, I'd like to get credit when I occasionally get one right.
Jake
------------------
1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9
Thread
Thread Starter
Forum
Replies
Last Post