need help with comp ratio
brings his heater.
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Need To Get Quicker
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Scott, we have been talking about this the last few days at the shop and we haven't found anyone that knows of any type of device that would work correctly. I know they have one to check the cubic inch size of an engine, but not the actual compression ratio. Do you have a picture of this tool? Maybe a web link? I would love to learn more about this thing. We might have to get one for the shop. 
Pro 5oh
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This tool is some what similar to what I use..... Notice the inside numbers lower numbers....
First I test the cyl.'s all of them for the pressure (leak down)
Then read it from the smaller numbers towards the middle of the gauge...add them up and divide them by 8 and should have a round about of what CR I should have.
First I test the cyl.'s all of them for the pressure (leak down)
Then read it from the smaller numbers towards the middle of the gauge...add them up and divide them by 8 and should have a round about of what CR I should have.
brings his heater.
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the outside numbers are pounds per square inch
the inside are kilopascal, both are units of pressure.
1 lb per sq in. equals 6.895 kPa
basically one is standard one is metric.
your formula doesnt work, you may as well throw a dart at a dart board, see where it lands to calculate compression ratio, it would be just as accurate.
the inside are kilopascal, both are units of pressure.
1 lb per sq in. equals 6.895 kPa
basically one is standard one is metric.
your formula doesnt work, you may as well throw a dart at a dart board, see where it lands to calculate compression ratio, it would be just as accurate.
Last edited by rubberneck; Aug 5, 2005 at 06:28 AM.
brings his heater.
Joined: Oct 2002
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Originally Posted by racingtheburg
Well I picked up this trick through an engine builder that does pretty well works for me ...
who is it, i would hate to accidentally use them for engine work
Registered User
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There is no way that you can screw anything into your spark plug hole and it tell you the compression ratio of the motor. There are too many variables like cylinder head chambers,camshaft design, cam timing ,valve overlap, and how fast the starter is spinning the motor. In the past I had a motor that was exactly 13 to 1 . The first camshaft that I had in it ,had a cranking compression of 240psi. The only thing I changed was the camshaft to a larger nitrous cam and the cranking compression dropped to 185. The only correct way to accurately calculate compression ratio is to dissassemble the motor.
