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Forum namePerformance/Engine
Topic subjectCompression test results
Topic URLhttps://forums.2gnt.com/dcboard.php?az=show_topic&forum=i5&topic_id=135555
135555, Compression test results
Posted by xxsoccerguy55xx, Nov-28-11 05:55 PM
I ran a compression test today. The outcome was:
cylinder 1 = 180
cylinder 2 = 155
cylinder 3 = 180
cylinder 4 = 165

The engine only has about 1200 miles on it. The motor got a new crank, bearings, and rings. I figure that the rings should have seated by now. The car was shut off for about 2 hours before we ran the test. May it not have been warm enough. I plan to go turbo in the spring. I have most the stuff for the kit already so I really want to so it. Do you guys think it is pointless because of the results of the compression test? Think I should wait a little longer to see if it changes? Any opinions would be great.
135556, RE: Compression test results
Posted by CODE4, Nov-28-11 06:03 PM
So you bought a new crank for the motor, yet re-used the old, stock rods and pistons?

What are your piston-to-cylinder wall clearances? Ring end gaps?
135557, RE: Compression test results
Posted by xxsoccerguy55xx, Nov-28-11 06:05 PM
it needed a new crank..........
135560, RE: Compression test results
Posted by CODE4, Nov-28-11 06:13 PM
Originally posted by xxsoccerguy55xx
it needed a new crank..........


Are you going to answer the rest of the questions?
135572, RE: Compression test results
Posted by xxsoccerguy55xx, Nov-28-11 07:43 PM
Originally posted by CODE4
Originally posted by xxsoccerguy55xx it needed a new crank..........
Are you going to answer the rest of the questions?


I dont remember the numbers. It was all in spec though. The gap came pre gapped and i double checked and it was the right gap according to the factory service manual.
135558, RE: Compression test results
Posted by teklein, Nov-28-11 06:09 PM
Did you hold the throttle open while cranking?

Did you hone before putting new rings in?
135559, RE: Compression test results
Posted by xxsoccerguy55xx, Nov-28-11 06:11 PM
no, recently reading though i did see you are suppose to hold open the throttle, would it make my numbers fluctuate, like they did? Im going to check it out tommorrow and make sure to keep the throttle open.
135561, RE: Compression test results
Posted by xxsoccerguy55xx, Nov-28-11 06:14 PM
And yes i did get it honed.
135574, RE: Compression test results
Posted by Broke4going, Nov-28-11 08:11 PM
some people leave the gap "as is" if they are within spec, I have my blocks machine honed for precision and then I make sure all of the ring gaps are filed to the exact same measurement whilst being in spec.

I know this may not account for the large % discrepancy just my two cents. Also,a failing or worn out tester can produce intermittent results. I use this one to eliminate that:

http://www.google.com/products/catalog?q=compression+tester&hl=en&client=firefox-a&rls=org.mozilla:en-US:official&channel=s&prmd=imvns&bav=on.2,or.r_gc.r_pw.,cf.osb&biw=1920&bih=1012&um=1&ie=UTF-8&tbm=shop&cid=12913438149401636417&sa=X&ei=C0zUToKuDYbAtgeIppG7Ag&ved=0CMEBEPMCMAk

at any rate, I guess we'll see what your new numbers are w/throttle open.
135604, RE: Compression test results
Posted by venge24, Dec-07-11 12:16 AM
Random question, did you check your oil/ coolant? It could be a head gasket problem..
135605, RE: Compression test results
Posted by xxsoccerguy55xx, Dec-07-11 01:10 PM
Yes i did check the oil. No antifreeze at all. It has a brand new head gasket, so unless something I installed didnt seat correctly then it shouldnt be the problem. You think it could be some leaky valves?
135606, RE: Compression test results
Posted by venge24, Dec-07-11 04:39 PM
could be, diid you lap the valves? did you replace the valve seals?
136137, RE: Compression test results
Posted by xxsoccerguy55xx, Feb-29-12 07:47 AM
Yes new valve seals, I didnt lap the valves, looking back i wish i had done that. I am thinking that the valves just arent sealing 100%