james singleton
Well-known member
I have a question concerning "compression tests results" that I took this last week. I hope that you won't mind that these compression tests were on a Chevy Inline 6 (230ci) and not a Ford Inline 6, which I also have (a 200ci) and post on here regularly, but here goes: My first time around on taking compression tests on the 230ci engine, I disarmed the coil, opened the carb throttle plate, and then tested one cylinder at a time, with the other 5 spark plugs still in the block. Here were the results, or the #'s: (**Note: according to the engine spec's on the 230ci engine the compression is 130psi) #1-116, #2-135, #3-130, #4-114, #5-122, #6-124. Then I did a followup compression test(s) where I removed all of the spark plugs before I started testing each individual cylinder, and here are the results: #1-90, #2-90, #3-100, #4-90, #5-100, #6-95.!
Here is my question on these numbers. What would be the explanation for why the numbers are larger on the first set of tests results, where all of the spark plugs are still in the block (except for the cylinder I am testing), than on the second set of test results where all of the spark plugs have been removed. I am sure there is a reasonable explanation??? Does it have to do with the fact that the engine turns over easier when "all of the plugs" are removed??? Thanks for any explanations. James
Here is my question on these numbers. What would be the explanation for why the numbers are larger on the first set of tests results, where all of the spark plugs are still in the block (except for the cylinder I am testing), than on the second set of test results where all of the spark plugs have been removed. I am sure there is a reasonable explanation??? Does it have to do with the fact that the engine turns over easier when "all of the plugs" are removed??? Thanks for any explanations. James