'87quest Posted May 4, 2015 Report Share Posted May 4, 2015 I just got 500 miles on my new engine and felt like doing a compression test. First of all I rebuilt the engine this past winter with forged wisecos, balanced rods, crank turned 10/10, block honed and decked, ajusa head gasket, arp head studs, new m28 head from Randy, new stainless valves and Schneider valve springs. All the machining and head assembly was done by a very reputable machine shop. Me and my future father in law (machinist of 25 years) assembled everything. The car has been running great so far (other than a few pita power steering leaks) but I felt like trying out my new compression tester. My results were 110, 105, 107, 111. I was expecting them to be more around 130-140ish... Should I be worried?? I had the throttle wide open when cranking and all plugs pulled btw. Or maybe my cheap US General compression tester kit isn't very accurate? Thanks in advance guys.. Hopefully I'm stressing over nothing! Drake Link to comment Share on other sites More sharing options...
JohnnyWadd Posted May 4, 2015 Report Share Posted May 4, 2015 Perform the test on a warm engine? Link to comment Share on other sites More sharing options...
importwarrior Posted May 4, 2015 Report Share Posted May 4, 2015 OOPS Link to comment Share on other sites More sharing options...
speedyquest Posted May 4, 2015 Report Share Posted May 4, 2015 (edited) importwarrior you should probably read the whole post man lol. He mentions that he did. Edited May 4, 2015 by speedyquest Link to comment Share on other sites More sharing options...
'87quest Posted May 4, 2015 Author Report Share Posted May 4, 2015 Engine was fairly warm, yes throttle was wide open, pulled all plugs, did not pour oil into the cylinders. I don't think it could be the rings.. I have no blow by or anything, no smoke. Link to comment Share on other sites More sharing options...
scott87star Posted May 4, 2015 Report Share Posted May 4, 2015 Cam could be off a tooth. Link to comment Share on other sites More sharing options...
Dad Posted May 4, 2015 Report Share Posted May 4, 2015 I would be thinking of 140 also. Dad Link to comment Share on other sites More sharing options...
'87quest Posted May 4, 2015 Author Report Share Posted May 4, 2015 Cam isn't off, timing is set at 10 BTDC. Thats what I was thinking too Randy.. I've been reading some reviews of my harbor freight compression tester and a lot of guys have complained that it reads low compared to a high quality tester, so I'm hoping thats the case and will borrow/buy a better one this week. Link to comment Share on other sites More sharing options...
JohnnyWadd Posted May 6, 2015 Report Share Posted May 6, 2015 importwarrior you should probably read the whole post man lol. He mentions that he did. I must had eye problems I didn't see if he mention it being hot or cold in the O.P. I just got 500 miles on my new engine and felt like doing a compression test. First of all I rebuilt the engine this past winter with forged wisecos, balanced rods, crank turned 10/10, block honed and decked, ajusa head gasket, arp head studs, new m28 head from Randy, new stainless valves and Schneider valve springs. All the machining and head assembly was done by a very reputable machine shop. Me and my future father in law (machinist of 25 years) assembled everything. The car has been running great so far (other than a few pita power steering leaks) but I felt like trying out my new compression tester. My results were 110, 105, 107, 111. I was expecting them to be more around 130-140ish... Should I be worried?? I had the throttle wide open when cranking and all plugs pulled btw. Or maybe my cheap US General compression tester kit isn't very accurate? Thanks in advance guys.. Hopefully I'm stressing over nothing! Drake Engine was fairly warm, yes throttle was wide open, pulled all plugs, did not pour oil into the cylinders. I don't think it could be the rings.. I have no blow by or anything, no smoke. Could try it just for diagnostic purposes it would help narrow down the issue. I have see the Harbor Freight testers read low too. Definitely worth a double check with the better one. Link to comment Share on other sites More sharing options...
speedyquest Posted May 6, 2015 Report Share Posted May 6, 2015 That was the only part of importwarriors question he didn't talk about, everything else he mentioned. Link to comment Share on other sites More sharing options...
JohnnyWadd Posted May 6, 2015 Report Share Posted May 6, 2015 That was the only part of importwarriors question he didn't talk about, everything else he mentioned. Oh I didn't see a question i just saw this..... OOPS Link to comment Share on other sites More sharing options...
importwarrior Posted May 6, 2015 Report Share Posted May 6, 2015 yes i need to read the entire post before answering or asking questions..... Link to comment Share on other sites More sharing options...
ucw458 Posted May 9, 2015 Report Share Posted May 9, 2015 I have 2 compression testers and they both give different readings. What I found was the tester with a 12" hose reads lower than the short one you press into the plug hole. They read about 30 psi different. The short one is more accurate but requires more skill to hold it in place to get a good seal on the plug hole. Link to comment Share on other sites More sharing options...
psu_Crash Posted May 9, 2015 Report Share Posted May 9, 2015 I've also had testers (even the same one) read wildly different. You should grab another one and take readings again. I took some fittings and made an adapter to connect the tester to my compressor and found one was reading about 30 low. Link to comment Share on other sites More sharing options...
'87quest Posted May 9, 2015 Author Report Share Posted May 9, 2015 Thanks guys I'm going to Sears today to get a craftsman tester. From the reviews I've read they are much more accurate/reliable. Link to comment Share on other sites More sharing options...
'87quest Posted May 9, 2015 Author Report Share Posted May 9, 2015 Just want to make sure everything is healthy before cranking the S16g up to 20 psi Link to comment Share on other sites More sharing options...
Malykaii Posted May 10, 2015 Report Share Posted May 10, 2015 I rebuilt my motor and got about 120 all around? Cant remembember the exact amount, it was low. Then I realized I have aftermarket pistons. Aftermarket producers tend to make their pistons have a lower compression ratio for some reason. Just a thought. Link to comment Share on other sites More sharing options...
Malykaii Posted May 10, 2015 Report Share Posted May 10, 2015 Also, if you really want to investigate, try a leakdown tester. Link to comment Share on other sites More sharing options...
'87quest Posted May 15, 2015 Author Report Share Posted May 15, 2015 Craftsman tester yielded 140,137,138,140. Much better! Thanks guys! Link to comment Share on other sites More sharing options...
Dad Posted May 15, 2015 Report Share Posted May 15, 2015 Great news Enjoy! Link to comment Share on other sites More sharing options...
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