new pistons old rings - where did my oil go??
Jun 3, 2009, 11:09 AM
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new pistons old rings - where did my oil go??
so timing belt went out, damaged the pistons and bent valves (no cylinder or head damage). replaced those and kept the undamaged old rings in the same cylinder and orientation to preserve the seal. fast forward 100 hard miles and 1 qt of oil burnt. pistons look wet, plug threads are wet, but the compression and leak down numbers don't look all that worrisome to me. any ideas where the oil might be coming from?
Cyl - Compression - Compression + oil thrown in cylinder - Leakdown
C1 165 175 10%
C2 175 185 8%
C3 180 190 6%
C4 175 185 8%
Cyl - Compression - Compression + oil thrown in cylinder - Leakdown
C1 165 175 10%
C2 175 185 8%
C3 180 190 6%
C4 175 185 8%
Jun 3, 2009, 11:30 AM
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valve stem seals are new replacements. there was an issue with them getting pulled off but not after a change to beehives from duals. there is no smoke at startup or vacuum indicative of seals, and none visible under load either. besides it's my understanding that valve seals won't result in the kind of consumption we are talking about here.
Jun 3, 2009, 11:38 AM
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oh they were replaced with an identical set of the same after-market pistons. there were some very slight size differences in piston diameter between old and new, but nothing i'd imagine would affect the rings. clearances were pretty much .004" on all.
Jun 3, 2009, 12:53 PM
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to avoid having to hone the block in situ and risk removing more material in and uneven fashion than needed and ending up with a clearance issue. the original pistons were not stock they were already 85.5 aftermarket of the same type. the two pistons that were different in size were .002-.003 larger than the old ones.
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Jun 3, 2009, 04:53 PM
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I think it was a poor decision to use the old rings. At the minimum, you could have just used a ball hone and sized your new rings it came with if you were worried about pulling the engine to have it honed with a machine. I have found that even though you purchase the same type piston for the correct bore, the actual size varies slightly. So with that size change, the current rings wouldn't have the same gap as before.
Do a leak down test, that will better determine if there is something not quite right and help you pinpoint the issue. A compression test will only tell so much.
Good luck.
Aaron
Do a leak down test, that will better determine if there is something not quite right and help you pinpoint the issue. A compression test will only tell so much.
Good luck.
Aaron
Last edited by WHTEVO; Jun 3, 2009 at 04:56 PM.
Jun 3, 2009, 05:31 PM
#10
I think it was a poor decision to use the old rings. At the minimum, you could have just used a ball hone and sized your new rings it came with if you were worried about pulling the engine to have it honed with a machine. I have found that even though you purchase the same type piston for the correct bore, the actual size varies slightly. So with that size change, the current rings wouldn't have the same gap as before.
Do a leak down test, that will better determine if there is something not quite right and help you pinpoint the issue. A compression test will only tell so much.
Good luck.
Aaron
Do a leak down test, that will better determine if there is something not quite right and help you pinpoint the issue. A compression test will only tell so much.
Good luck.
Aaron
