compression tests?

[duneracerweston]

Is there any way to tell what compression the motor is other that knowing what piston is in it?

 

[duneracerweston]

Or is a copression tester the only way to tell?

 

[Deuce]

Compression is a whole slew of things. Piston comes into play, so does the head if it was shaved or not, gasket thickness, etc. The most reliable way to know what your compression is, is by using a tester. This will give you a certain psi reading that you could use to figure out how healthy the top end is, and how much squeeze it has as well.

 

[duneracerweston]

Well how can you translate psi int a compression ratio?

 

[buzzy613]

there might be a mathmatic formula for that but 9:1 compresion ratio puts out 125psi i think 10:1 will be around 160, and 12:1 will be 180+, thats my guess

 

[paulie1959]

You probably can cc it with heavy oil and a large syringe through the plug hole, set piston TDC compression stroke and measure cc injected into bottom of plug hole threads, displacement 348cc divided by combustion cc 37.826cc = 9.2 to 1 stock, then you'll have to get the oil out.

 

[paulie1959]

you cant tell by PSI because all gages are not accuate, they might be 20 psi off, a gage is good for multi cylinder because you can compare between cylinders to find the weak one.