tristanlee85 Posted May 28, 2008 Report Share Posted May 28, 2008 7psi doesn't quite feel like 7psi probably because my compression is 145 - 170 - 163 - 178. How could I determine whether it's rings or valves? I am assuming a leakdown test would tell me if my rings are bad, yes? What about valves? Quote Link to comment Share on other sites More sharing options...
Doug1647545489 Posted May 28, 2008 Report Share Posted May 28, 2008 7psi doesn't quite feel like 7psi probably because my compression is 145 - 170 - 163 - 178. How could I determine whether it's rings or valves? I am assuming a leakdown test would tell me if my rings are bad, yes? What about valves? Leak down test. You can hear where it's leaking. Crankcase, exhaust, intake, etc... Quote Link to comment Share on other sites More sharing options...
tristanlee85 Posted May 28, 2008 Author Report Share Posted May 28, 2008 I'll give that a shot. I didn't get a valve job on the head, but I used lapping compound to try and create a nice mating surface between the valves and the head. Quote Link to comment Share on other sites More sharing options...
Doug1647545489 Posted May 28, 2008 Report Share Posted May 28, 2008 I'll give that a shot. I didn't get a valve job on the head, but I used lapping compound to try and create a nice mating surface between the valves and the head. Did you fill the ports with water and watch for leaks? Quick and easy way to see if you have a good seal. Quote Link to comment Share on other sites More sharing options...
tristanlee85 Posted May 28, 2008 Author Report Share Posted May 28, 2008 That I didn't do. :-\ Quote Link to comment Share on other sites More sharing options...
Doug1647545489 Posted May 28, 2008 Report Share Posted May 28, 2008 You can also pour a little oil in the cylinder you are compression checking. If compression comes back it's probably rings. Quote Link to comment Share on other sites More sharing options...
tristanlee85 Posted May 28, 2008 Author Report Share Posted May 28, 2008 Well too much work to do for tonight. I hope it isn't the rings. Thanks for the info. Quote Link to comment Share on other sites More sharing options...
tristanlee85 Posted May 28, 2008 Author Report Share Posted May 28, 2008 Or maybe I'll just run 25psi instead of 20. That should compensate for the low compression. Quote Link to comment Share on other sites More sharing options...
AJ Posted May 28, 2008 Report Share Posted May 28, 2008 You can also pour a little oil in the cylinder you are compression checking. If compression comes back it's probably rings. doesn't always work, i did that to a L6 and it brought the compression back up but it was a burnt valve and the little bit of oil that was forced out the exhaust port just cranking it over was enough to seal the valve to the head and take it from 120psi to 155psi. i was glad i checked the head before taking the engine out for a rebuild. Quote Link to comment Share on other sites More sharing options...
Doug1647545489 Posted May 28, 2008 Report Share Posted May 28, 2008 doesn't always work, i did that to a L6 and it brought the compression back up but it was a burnt valve and the little bit of oil that was forced out the exhaust port just cranking it over was enough to seal the valve to the head and take it from 120psi to 155psi. i was glad i checked the head before taking the engine out for a rebuild. Yeah I know it's a ghetto way to do it. Leak down is the proper test procedure. Quote Link to comment Share on other sites More sharing options...
Reed44 Posted May 28, 2008 Report Share Posted May 28, 2008 Compression and leak down will determine your problem. Just make sure you have the valves (TDC) closed on the piston(s) you are checking. Is your car smoking? What color is it? I am leaning more towards bad rings. Quote Link to comment Share on other sites More sharing options...
tristanlee85 Posted May 28, 2008 Author Report Share Posted May 28, 2008 This engine also has 50 - 100 miles on it (not accurate because my speedometer didn't work for a few drives). Should I give it a few hundred more miles before tearing into the engine? I don't expect the 145psi cylinder to jump up to 180psi, but maybe there is a chance it could increase a little. 170psi doesn't worry me. I'm just worried about consistency. Quote Link to comment Share on other sites More sharing options...
tristanlee85 Posted May 28, 2008 Author Report Share Posted May 28, 2008 Compression and leak down will determine your problem. Just make sure you have the valves (TDC) closed on the piston(s) you are checking. Is your car smoking? What color is it? I am leaning more towards bad rings. No smoke at all. None at idle, none under boost, and none under a hard engine brake. Quote Link to comment Share on other sites More sharing options...
AJ Posted May 28, 2008 Report Share Posted May 28, 2008 This engine also has 50 - 100 miles on it (not accurate because my speedometer didn't work for a few drives). Should I give it a few hundred more miles before tearing into the engine? I don't expect the 145psi cylinder to jump up to 180psi, but maybe there is a chance it could increase a little. 170psi doesn't worry me. I'm just worried about consistency. talk to us when you have 500 on it. Quote Link to comment Share on other sites More sharing options...
tristanlee85 Posted May 28, 2008 Author Report Share Posted May 28, 2008 Sounds good. We'll do. Thabnks guys. Quote Link to comment Share on other sites More sharing options...
AJ Posted May 28, 2008 Report Share Posted May 28, 2008 ok well if it makes it to 500 miles from what a little bird just told me. Quote Link to comment Share on other sites More sharing options...
tristanlee85 Posted May 28, 2008 Author Report Share Posted May 28, 2008 Well I won't lose sleep over it. I have about a 50/50 shot of making it that far. Quote Link to comment Share on other sites More sharing options...
tristanlee85 Posted June 10, 2008 Author Report Share Posted June 10, 2008 I changed my plugs tonight and did another compression test. Somehow I made it to 800 miles. Amazing. Anyway, now I've got 135 - 179 - 180 - 179. Is there any reason not to use this (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94190) as opposed to the $75 one at Jegs? Quote Link to comment Share on other sites More sharing options...
Guest Removed Posted June 10, 2008 Report Share Posted June 10, 2008 let me know what day you want me to run a leak down on it and ill bring mine home Quote Link to comment Share on other sites More sharing options...
Guest Hal Posted June 10, 2008 Report Share Posted June 10, 2008 I haven't had a problem with my Harbor Freight tester. If I had access to a better one, I would use it; that being said, I still use my Harbor Freight one. Quote Link to comment Share on other sites More sharing options...
tristanlee85 Posted June 10, 2008 Author Report Share Posted June 10, 2008 let me know what day you want me to run a leak down on it and ill bring mine home I am free every night this week after 6:00PM so whatever works for you. Quote Link to comment Share on other sites More sharing options...
Guest Removed Posted June 10, 2008 Report Share Posted June 10, 2008 i work till 8 wed then im off at 6 the rest of the week...pm me a number and we'll go from there Quote Link to comment Share on other sites More sharing options...
tristanlee85 Posted June 13, 2008 Author Report Share Posted June 13, 2008 Well Rob hooked me up, but we couldn't see much of a difference between my weak cylinder and a good one. My weak one leaked about 3% - 5% more. I did a compression test again with oil in each cylinder this time and they were all between 178 and 183. Thanks again, Rob. Quote Link to comment Share on other sites More sharing options...
Guest Removed Posted June 13, 2008 Report Share Posted June 13, 2008 Well Rob hooked me up, but we couldn't see much of a difference between my weak cylinder and a good one. My weak one leaked about 3% - 5% more. I did a compression test again with oil in each cylinder this time and they were all between 178 and 183. Thanks again, Rob. what was it dry? no prop man..just hit the trader rating Quote Link to comment Share on other sites More sharing options...
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