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Forum namePerformance/Engine
Topic subjectComprssion test results
Topic URLhttps://forums.2gnt.com/dcboard.php?az=show_topic&forum=i5&topic_id=129919
129919, Comprssion test results
Posted by gsgoingT, Mar-07-10 12:24 PM
HI, so today I did compression test. It came 120 on all four. Engine was warm when i did this, also I let engine turn about 4 times. Then I put some oil in spark plug holes and results were between 240 and 265. Now, after some research i came with two answers. One rings are bad. Second I have bad head gasket.
Another thing you might want to know is, when car is warming up, I get thick white smoke, but after some driving there is no signs of any smoke (my guess bad valve seals/guides?)
Block was rebuilt about 4k ago. JE 8:6:1 pistons(i think those are the #)with Total Rings, and eagle rods, head was not rebuild. I used Cometic Head Gasket (i heard someplace we should use mopar for best results). Pls let me know what are you thoughts. Thx
129920, RE: Comprssion test results
Posted by CODE4, Mar-07-10 01:38 PM
If adding a bit of oil dramatically improves the compression results it usually indicates worn or unseated rings.

Thick white smoke is usually not indicative of worn valve stem seals - a worn valve stem seal will allow oil to be burned in the combustion chamber creating a blue/grey smoke.

Does your coolant level drop after consistent driving (indicating a bad HG?)

Bottom line is if you are producing smoke in any real quantity, a fluid level will suffer at some point. That will tell you what is failing.
129921, RE: Comprssion test results
Posted by gsgoingT, Mar-07-10 01:53 PM
I'm not loosing any coolant, but I'm loosing oil. Also when i did rebuild, I did not hone block, could this be the problem?

http://forums.2gnt.com/dcboard.php?az=show_topic&forum=5&topic_id=125487&mode=full
129922, RE: Comprssion test results
Posted by CODE4, Mar-07-10 02:09 PM
Originally posted by gsgoingT
I did not hone block, could this be the problem?


Very likely.
129924, RE: Comprssion test results
Posted by 420agreenvilleSC, Mar-07-10 04:56 PM
imagine falling down a cylinder. Don't you want ridges to help you grab on to help prevent from falling? That's what honing does. Lets the rings 'grab' the walls for seating. wierd analogy, yea I know.
129925, RE: Comprssion test results
Posted by gsgoingT, Mar-07-10 05:09 PM
I understand, now the question is; Now what?? ;)
I don't have place to take engine out. I could take head, but not the whole engine.
Could i take head off, take oil pan off, take rods/pistons out, then use honing tool http://www.summitracing.com/parts/WMR-W80560/?rtype=10
put new rings on (or could i reuse rings i have on now) and assemble engine?
129927, RE: Comprssion test results
Posted by 420agreenvilleSC, Mar-07-10 06:15 PM
either way, but it's worlds easier if you remove the entire long block, disassemble, reassemble, reinstall.
129929, RE: Comprssion test results
Posted by CODE4, Mar-07-10 07:44 PM
Originally posted by gsgoingT
I understand, now the question is; Now what?? ;)


Well, bottom line is you need to hone the cylinders and buy new rings. This is assuming there is no excess tolerance wear that has occurred since your build. After honing, however, you need to scrub the hell out of the cylinder walls and ensure they are sanitary enough to eat off of. This could be performed with the shortblock in the engine bay, but I do think it is practical.
129930, RE: Comprssion test results
Posted by gsgoingT, Mar-07-10 07:52 PM
thx
129931, RE: Comprssion test results
Posted by teklein, Mar-08-10 03:55 AM
Also get your head milled *at least*.
129936, RE: Comprssion test results
Posted by Star Turbo Talon, Mar-08-10 10:29 AM
Engine has to come out, period. LEaving it in will get debris in the oil passages which will damage the bearings on startup.
129942, RE: Comprssion test results
Posted by gsgoingT, Mar-08-10 05:32 PM
ok, thx