Im done assembling a b18c for boosting. How would you compression test a motor with 9:1 ratio pistons? How would that work? Wouldnt you get low compression readings?

 

It might read a bit lower, but you're mainly looking for uniformity across all cylinders. Provided, of course, that they arent all like 100psi or something

 

it should be 190-200psi but u want them to all be the same not 195-190-170-195 lol. my b17 has a compression ratio of 9.7:1 and is 200 straight across and my ls is 9.2:1 with 185 or 190 straight across i dont remember

 

The problem with compression testers is that they're like dynos and all give different readings. The different readings aren't a problem if you're using the tool for exactly what it's designed for and that's the testing you are doing at the time, not comparrison to other peoples results.

Cliff notes- You aren't supposed to compare compression tester numbers anymore than you are dyno numbers. As long as they are uniform across the cylinders, that's all that matters. If you want to calculate your ACTUAL comp ratio, you need to do some measuring internally.

 

Well thank you guys for your input. Its a first for everything with me. Thanks again i appreciate it!

 

If you just got done assembling it then you haven't even fired it? You need to seat the rings before you go trying to compression test it or the results will be less then satisfying. Remember to compression test with the ignition system disabled, engine at operating temperature, and throttle wide open also.