skibumm100 Posted February 12, 2012 Share Posted February 12, 2012 The car: 98 Legacy GT The engine: EJ25 The Problem: I lost a timing belt idler a couple years back and bent a couple of valves. I pulled the engine out, took the heads off and had an automotive machine shop replace the bent valves, do a complete valve job and flatten the head gasket surface. I put it all back together using factory parts, replacing anything and everything that you should replace. I made a mistake and overtorqued one of the headbolts so I backed it off and re-torqued it. The car ran great for about a month. It then starts puking the water out of the overflow. Blown HG. Bubbles in the coolant reservoir. Fast forward a couple years and I've decided it's time to fix this thing and sell it. I charged the battery and fired it up. I drive it out of it's home in the garage and let it warm up. Once it's warmed up I shut it down, pull the plugs, prop the throttle open and check the compression. Acceptable compression range is 137-176 PSI. On my engine the compression ranged between 210 -240 PSI. No cylinder(s) was noticably low. The plugs looked good with the possible exception of one. It's color was good but it had a little build up on the ground electrode. I know these engines are finicky on head gaskets and are prone to blowing them. I thought about stacking two head gaskets to drop the compression down some but I'm a little concerned since these engines are already prone to HG failure. Does anyone else have experience with compression numbers this high? Am I concerned for nothing? I already have to replace the HG's so unless I can figure out which side it is I need to do both sides. Thanks for reading! Quote Link to comment Share on other sites More sharing options...
idosubaru Posted February 12, 2012 Share Posted February 12, 2012 that sucks doing it all over again. positive the HG's are bad huh? with all that work they should have held? overtorqued - how badly, how do you know (just fishing for a good story here LOL)? i wouldn't stack subaru HG's, never heard of it before and sounds like a generally terrible idea, but i've never tried it either. as to compression readings - the resurface increased compression some, maybe someone can chime in exactly how much? if all of them are affected fairly equally then this seems highly likely. if there's fluids in the chamber i believe i've had that up compression before. but that's not the case here, you mentioned plugs were okay and it would be very odd for all cylinders to increase a similar amount. do you know what headgasket was used when it was replaced? there's a really thin headgasket and a thick one - just use the one ending in 610, that's the one i prefer for this engine anyway - it's MLS style and very thick, it will decrease the compression ratio some verses the thinner one. Quote Link to comment Share on other sites More sharing options...
skibumm100 Posted February 12, 2012 Author Share Posted February 12, 2012 Hi GG! Thanks for your help in the past. I'm not sure what the overtorque was. It didn't click. I misadjusted the torque wrench and it was the first head bolt on the final torqueing. As I was turning the wrench I was thinking to myself "this thing should've clicked by now", so I stopped and checked my setting. It was definately higher than the final torque but I didn't leave it for more than a minute. I'm pretty sure it's a blown HG based on the way it acted when it puked the water out. I was careful to raise the front of the car on ramps and to burp the hoses as it warmed up the first time after the original work. I also drilled a bigger by-pass hole in the thermostat and located it at the top. I did that after the first time it puked. The head gasket I put in the car was the OEM one that comes with the kit from Genuine Subaru Parts. I don't know the part number of the gasket itself. When I warmed the engine before doing the compression readings I let it get warm but not real hot. I think I might let it get hotter today and see if I can get it to barf and then check the compression. I really don't want to do both sides if I don't need to. Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted February 12, 2012 Share Posted February 12, 2012 if you numbers come back the same, or similar, i would probably try a different tester. unless you have absolute confidence in yours. my guess is it gets used so rarely you wouldn't really know if it was out of whack. just a thought. i would hate to see you do a lot of work based on bad info. i think i have heard that high, a little high, compression numbers are possible if the timing is off. but your are so high, or seem to be to me, that i doubt that is the cause. Quote Link to comment Share on other sites More sharing options...
skibumm100 Posted February 12, 2012 Author Share Posted February 12, 2012 Good point John. I have another gauge I can try. The one with my compression tester isn't very high quality and it sits in the tool box drawer for a long time between uses. I'm still a litle concerned about the bubbles, though. I didn't work on it today since it was so cold out. It'll be a couple weeks before I can get back at it again. Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted February 14, 2012 Share Posted February 14, 2012 I made a mistake and overtorqued one of the headbolts so I backed it off and re-torqued it. Big No-no. You squished the gasket in one corner. If you had done all 6 bolts that way it might not have been an issue. You could have also warped the head. Not sure about the high compression numbers. 210 psi I wouldn't worry about, but 240 is getting up there. I would be checking the timing. I don't know what's normal for that engine though. Quote Link to comment Share on other sites More sharing options...
nipper Posted February 14, 2012 Share Posted February 14, 2012 210 is too high, considering it is supposed to be 180ish. I would double check the compression tester. Other possability is the timing is off a tooth (works both ways). Unless someone got really agressive with the cylinder head deck machining. Quote Link to comment Share on other sites More sharing options...
CoupedUpSubie Posted February 14, 2012 Share Posted February 14, 2012 I am curious how the timing being off 1 tooth would effect the compression. To me it sounds like the heads needed a good amount taken off or the person doing the work took too much. Also the two different HG thicknesses could be the culprit. Thinner gasket and higher pressures could have caused your quick HG failure. Quote Link to comment Share on other sites More sharing options...
nipper Posted February 14, 2012 Share Posted February 14, 2012 Doesnt always, but valves start to open before the piston reaches top dead center. Delay that opening you have a clsed cylinder longer so more compression. http://www.cdxetextbook.com/engines/comp/vlves/valvetimingdiagram.html Quote Link to comment Share on other sites More sharing options...
ivans imports Posted February 14, 2012 Share Posted February 14, 2012 i have my own planer i just biult a engine that i planed the block surface two mutch and pistons hit heads to fix i take the 98 twin cam head gasket and break it down into its indvidual layers thiss makes verry good head shims have done it many times i put 10 lbs of boost and 75 shot of nitrous on that engine no problems i do find that when i plane a block or head that they ushaly need to be planed alot and i use avionic form agasket on evry head gasket i do over 100 thiss year Quote Link to comment Share on other sites More sharing options...
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