subynut Posted January 24, 2006 Share Posted January 24, 2006 Low compression. Even after the rebuild, I STILL have low compression: 1: 100 2: 150 3: 70 4: 90 How is this possible???? They are all supposed to be around 150. Here's what I did: Tore engine completely apart. Had heads worked on: one was bad, swapped that one. New rings. One piston had a callapsed skirt, replaced that one with one out of a SPFI engine. Cylinders still had some cross hatching on them, not much, but it was there. No signs of scratching or anything. New Napa gaskets. Couldn't afford Subaru gaskets at the time. I gots poor mileage, poor power, don't like to idle: can't make up it's mind if it wants to run at 1100 or 500 rpms. Anybody have any ideas? I'm at a loss as to what's wrong. Some people have told me that I may have bad lifters. I got's no tick. Could they be bad? At 50 bucks a pop, I dont' want to swap them unless I absolutly have to. Quote Link to comment Share on other sites More sharing options...
NoahDL88 Posted January 24, 2006 Share Posted January 24, 2006 make sure that you test the compression with the throttle at wide open, if its not it will read low. Also depending on how you number your cylinders, your passenger timing belt could be off 180, that hash mark has to be down when the drivers side is up. Also, the belts are not set to TDC, they are set to 3 small marks somewhere else on the flywheel. Maybe the rings are just not seated well yet. Quote Link to comment Share on other sites More sharing options...
subarunuts Posted January 24, 2006 Share Posted January 24, 2006 Bad lifters would cause your compression to be higher, not lower, as the valve would not open as far as it should. You need to check three things for compression - valve seats, rings, and head gaskets. Rings are new.... did you make sure the gaps are not aligned? Did you check to see that the valve seats or valves are not burned? That is where I would start. Tear the heads off and have the valves checked to make sure they seat properly. I'm assuming you used new head gaskets? I prefer the Fel-Pro perma-torque's myself. I've pulled compression as high as 200 - 210 off an EA81, so your numbers are all on the low side, and definately not within that 90% mark of each other. Quote Link to comment Share on other sites More sharing options...
subynut Posted January 24, 2006 Author Share Posted January 24, 2006 Compression test was done with throttle at WOT. T-belts are 180 out. Yes, I had the valves worked on while I had it apart. New headgaskets, and I made sure the rings were not aligned when I put them in. Before I cooked the engine, I was getting over 150 on all 4. I've been driveing it for about 2 weeks. I had one noisey lifter when I first started it up, the vac guage was bouncing to the tick, two days later, it dissapeared and idle improved, but still noware near what it's supposed to be. Vaccume is wandering at about 13-15 at 1200rpm, will steady out above 2000rpm. Quote Link to comment Share on other sites More sharing options...
NoahDL88 Posted January 24, 2006 Share Posted January 24, 2006 Did you hone the cylinders at all? is it the same short block? If you are using the same block without roughing up your cylinders, thats your problem, new rings won't seat on a smooth cylinder. try adding a squirt of oil to the cylinder and re try the compression test, if that helps you got a leak somewhere, which i would say is the cylinder, as you said you had the valves and heads worked on. How many times can you say cylinder in one sentence? Quote Link to comment Share on other sites More sharing options...
subarunuts Posted January 24, 2006 Share Posted January 24, 2006 I might start suspecting a bad valve job then.... maybe they didn't seat them properly or something. That's just weird. Only other thing I could think of.... did you have the heads milled? Sometimes when those heads are overheated they will warp to a point where they will never seal properly again once removed. They might need to be "trued-up" by a head shop before re-installation. Just a thought. Quote Link to comment Share on other sites More sharing options...
subarunuts Posted January 24, 2006 Share Posted January 24, 2006 Noah speaks the truth - bottle-brush hone at least for new rings - it acts like sandpaper and helps the rings to seat. Especially important on old engines because the cylinders are often no longer round, while the rings are. Quote Link to comment Share on other sites More sharing options...
subynut Posted January 24, 2006 Author Share Posted January 24, 2006 Yes, he checked them for truidy before he started working on them. Funny, they weren't warped at all, but the one that was bad, had major cracks on both the intake and exhaust ports. Quote Link to comment Share on other sites More sharing options...
NoahDL88 Posted January 24, 2006 Share Posted January 24, 2006 Yes, he checked them for truidy even if there round they still need to be honed Quote Link to comment Share on other sites More sharing options...
subynut Posted January 24, 2006 Author Share Posted January 24, 2006 Ok, no I did not hone the cylinders. I was told that a wet comp test doesn't work on a flat opposed engine. Quote Link to comment Share on other sites More sharing options...
NoahDL88 Posted January 24, 2006 Share Posted January 24, 2006 Ok, no I did not hone the cylinders. I was told that a wet comp test doesn't work on a flat opposed engine. Maybe it dosn't, but i'd hone those cylinders, and maybe get new rings, and try again. Quote Link to comment Share on other sites More sharing options...
subynut Posted January 24, 2006 Author Share Posted January 24, 2006 Ok, I'm gonna do a wet test, just to see what happens. Looks like I'll be tearing it apart again. Oh, what fun. Funny, it took me about 3 tries to get the Weber on there right too. Do I see a pattern here? Thanks guys! Quote Link to comment Share on other sites More sharing options...
NoahDL88 Posted January 24, 2006 Share Posted January 24, 2006 Happens to the best of us, i tried 3 different engines until i got one to run in my car. that was a fun 2 years. Quote Link to comment Share on other sites More sharing options...
kingbobdole Posted January 24, 2006 Share Posted January 24, 2006 granny shiftin, always double posting:rolleyes: Quote Link to comment Share on other sites More sharing options...
kingbobdole Posted January 24, 2006 Share Posted January 24, 2006 I totally disagree with the person that said bad lifters only cause increased pressure... I've seen lifters stuck at the top of their game, not compressable at all... I would think that the valve would stay open longer, causing lack of compression... If I'm not shot down as being nuts the firsty thing you might try(since it doesnt involve distrubing the HG) is to pull the cam carrier and pull the lifters and see if you can compress them... if you cant try soaking them. You said you had cracks in the head? That MIGHT be an issue as well.. Quote Link to comment Share on other sites More sharing options...
blownbimer Posted January 24, 2006 Share Posted January 24, 2006 Anyone done a leak down? find out where you loosing the compersion? Thanks Erik Quote Link to comment Share on other sites More sharing options...
subynut Posted January 24, 2006 Author Share Posted January 24, 2006 The head that had the cracks in it was the one I replaced. As far as the lifters, I know some of them I could compress and some I could not. Stupid question time: How do I do a leak down test? Quote Link to comment Share on other sites More sharing options...
blownbimer Posted January 24, 2006 Share Posted January 24, 2006 The head that had the cracks in it was the one I replaced. As far as the lifters, I know some of them I could compress and some I could not. Stupid question time: How do I do a leak down test? The ones I've used, you put the cly in question on TDC, then, you connect a fancy air tool to the spark plug hole.Im sure autozone rents them. When the air blows, you should be able to listen in the oil cap, air filter, and exhaust pipe, wherever you hear a hiss, thats where to start looking. Thanks Erik Quote Link to comment Share on other sites More sharing options...
shawnsbrat Posted January 24, 2006 Share Posted January 24, 2006 Ok, no I did not hone the cylinders. I was told that a wet comp test doesn't work on a flat opposed engine. Stop poking and hoping and do a simple leak down test to atleast see where its going.Pop your dist cap and point the rotor to the cylinder you want to check.Pull the plug,peek in and make sure that piston is perfectly at tdc. Make sure you prevent the crank from turning when you apply air pressure to the cylinder.Listen for air escaping from the throttle,listen at the tail pipe and remove the oil cap and listen for air getting past the piston. Good luck! Quote Link to comment Share on other sites More sharing options...
subynut Posted January 25, 2006 Author Share Posted January 25, 2006 Cool, that's the info I needed. I'll see what I find at the auto parts stores for that tool. Quote Link to comment Share on other sites More sharing options...
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