Compression test

R

Robert Legner

Member
I am preparing to do a compression on a 1950 8BA. I read in another thread that the throttle has to be open for the test. I am green at this so can someone describe the reason for the open throttle? I have heard of a test being taken without the open throttle and the reading was not good. I did a compression test and that showed good compression. Your thoughts.....
 
with the throttle closed the piston can not pull the air into the cylinder because of the restriction caused by the closed throttle, you need a full charge of air to get an accurate compression reading
 
I haven't seen a big difference with the throttle open or closed. If we were talking about a 400 c.i. high compression engine, yeah, I'm sure it makes a bigger difference. What kind of numbers did you get?
 
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