markman34 Posted February 3, 2005 Share Posted February 3, 2005 So I just did a compression test all the way around the engine and have noticed that two of the cylinders have far lower values than they should. The passenger side cylinders have 160 and 168 psi and at this point I was thrilled. When I got over to the drivers side, I ended up with one cylinder at 110 and one at 130 psi. Now I'm trying to figure out the problem. The car uses very little oil, and has ample power for a little guy. There is an obvious power balance vibration under heavy load. Other than these problems everything looks fine. Being that the problems are located on one side of the engine one might think that there was a HG issue but I just put the heads on this engine and everything looks and sounds fine.(as far a HG problems) No coolant use, no bubbles. Now, I'm wondering if there is a possibility that I have a cracked head that I did not notice when I put the heads on. Or, perhaps I missed the cam timing by one tooth on the belt. Or, maybe both cylinders on that side have worn piston rings. (the cylinders looked fine during assembly) Will I kill the engine driving it with such a power balance problem? I wonder because on my way home today the car died on the road. I pulled over and looked around and turned it over a couple times with no luck. After scratching my head for a few mins and continued attempts at starting it, the car fired up and ran fine for the remainder of the drive. Now I'm confused and concerned because I'm going to work in a couple days and I really ned reliability out of this car. Any help or insight would be greatly appreciated Thanks Quote Link to comment Share on other sites More sharing options...
ballitch Posted February 3, 2005 Share Posted February 3, 2005 well here are your possibilities, A, hg blown on driver side but you said it was okay. B, cam may be off by one tooth, but that would cause ALOT of vibration. C, worn piston rings, sounds like your best bet to me, had a similar problem in my 86 gl. D, worn or carbon coated valves or valve seats. E, cracked head or cracked in between valves head. thats the only things i can think of at this point. ~Josh~ Quote Link to comment Share on other sites More sharing options...
idosubaru Posted February 4, 2005 Share Posted February 4, 2005 check your timing - make sure your tensioners, pulleys and sprockets all look good and solid and appear to be working properly. doesn't sound like it's a tooth off, it would run terrible that way. i would also suspect the HLA's, this thing has them right? i've had seized HLA's that gave low compression...but DID NOT actually tick or tap or make any noise. i would suspect this before the head gasket. i had two cylinders on one side of my XT6 (3 cylinders per side) that had a bad HLA and bad compression associated with that HLA. i went back in and cleaned all of my HLA's, dissassembled and cleaned them all up. the two that were problematic would not come apart i tried a bunch of things and they were completely stuck, would not move or budge with treatments, heat, etc. i replaced them and compression was fine. now the easy way to tell, was that once the cam tower was off i noticed that two of the HLA's out of the 6 of them were not the same height. in other words i put a ruler across the top of them all and two fell short of the heigth of the rest of them, that was my first clue that it was HLA related. so maybe you can pull your cam tower on that side and see if you observe the same thing. Quote Link to comment Share on other sites More sharing options...
Mike386 Posted February 4, 2005 Share Posted February 4, 2005 I had the same compression readings on my spfi and it turned out to be a warped cylinder head. Pull the head and check the clearance with a perfect straight edge and a .005 inch feeler gauge; check the service manual for the procedure. The head will need to be resurfaced if the warp is not to severer, otherwise the head will have to be replaced. check your timing - make sure your tensioners, pulleys and sprockets all look good and solid and appear to be working properly. doesn't sound like it's a tooth off, it would run terrible that way. i would also suspect the HLA's, this thing has them right? i've had seized HLA's that gave low compression...but DID NOT actually tick or tap or make any noise. i would suspect this before the head gasket. i had two cylinders on one side of my XT6 (3 cylinders per side) that had a bad HLA and bad compression associated with that HLA. i went back in and cleaned all of my HLA's, dissassembled and cleaned them all up. the two that were problematic would not come apart i tried a bunch of things and they were completely stuck, would not move or budge with treatments, heat, etc. i replaced them and compression was fine. now the easy way to tell, was that once the cam tower was off i noticed that two of the HLA's out of the 6 of them were not the same height. in other words i put a ruler across the top of them all and two fell short of the heigth of the rest of them, that was my first clue that it was HLA related. so maybe you can pull your cam tower on that side and see if you observe the same thing. Quote Link to comment Share on other sites More sharing options...
BobBrumby Posted February 4, 2005 Share Posted February 4, 2005 to see if your rings are cause the comp. problem pull a pug squirt some oil down there and now take the comp reading. If it increases its worn rings. If compression doesnot change atleast youve ruled something out. Quote Link to comment Share on other sites More sharing options...
markman34 Posted February 4, 2005 Author Share Posted February 4, 2005 As far as checking the rings with some oil. I've always wondered how well that will work due to the fact that the piston is lying on it's side. I wonder if the majority of the ring will not get covered with the oil and the air will still get out. I have squirted some oil in there and did see a slight increase in the compression but this could be do to a small amount of fluid (that will not compress) left in the cylinder. Any comments on this possibility? It sure is a lot easier on a inline motor with a vertical throw as a small amount of oil will seal the ring far better. Another trick I've thought of is to pressurize the cylinder with compressed air and listen to where the air goes.(through the valves or into the crankcase) I have used this trick before to do valve maintenance on a v-8 with the heads attached. I could hear exactly where the air went. What is the consensus on the driving of the unbalanced engine? Will the vibration shake the engine to death? Should I not be driving it? I have the parts to re-fresh my other engine on order. I would be happy to run this engine until the other engine is built and ready to go. Quote Link to comment Share on other sites More sharing options...
markman34 Posted March 1, 2005 Author Share Posted March 1, 2005 So I have been able to get all the valves working properly and have seen the compression in the low cylinders come up. All cylinders are 170 - 160 PSI I think maybe the restriction caused by the not fully open valves limited the compression Quote Link to comment Share on other sites More sharing options...
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