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Cylinder leakdown higher after engine rebuild?
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So I spoke with Andrew today, I showed him the my oil analysis reports and told him my numbers from my leakdown test, and this was his response,
“I looked through the results and showed them to our builder as well. He made the same comments I had, 4-6% leakdown is about as good as we ever see. We looked through the build sheet and we did run the piston to wall clearance around .0035". All other clearances on that bottom end really look pretty normal to us. When the oil consumption makes the engine unusable then I would suggest getting concerned, but until then I don't see any reason to be all that concerned on this engine. I do agree that chromium likely comes from the top piston ring, I am not sure that material is anywhere else in the engine.”
I’m not well versed in piston wall clearance, but it .0035 wider than normal and thus the reason for slightly more leakdown?
still doesn’t really answer the question of why I am getting so much metal in my oil. Anyone else have any oil analysis reports from a rebuild who can shed light on their experiences?
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This is my Unbuild Journal and why we need an oil thread
https://nam3forum.com/forums/forum/m...nbuild-journal
"Do it right once or do it twice"
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If you were running stock pistons before the rebuild and forged CPs post re-build, then there will be increased oil consumption based on tolerances if I recall correctly.
As far as the increased metal I fear you will be chasing your tail for months to come based on your previous post about checking the oil so I don't see a resolution on the horizon, just endless postulating.2003.5 MT JB/B - CSL SCHRICK SUPERSPRINT EISENMANN JRZ SWIFT MILLWAY APR ENDLESS BBS/SSR DREXLER KMP SACHS RECARO AR SLON MKRS GSP DMG KARBONIUS CP AUTOSOLUTIONS KOYO
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Originally posted by jet_dogg View PostIf you were running stock pistons before the rebuild and forged CPs post re-build, then there will be increased oil consumption based on tolerances if I recall correctly.
As far as the increased metal I fear you will be chasing your tail for months to come based on your previous post about checking the oil so I don't see a resolution on the horizon, just endless postulating.
Found the specs
This is my Unbuild Journal and why we need an oil thread
https://nam3forum.com/forums/forum/m...nbuild-journal
"Do it right once or do it twice"
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Originally posted by jet_dogg View PostIf you were running stock pistons before the rebuild and forged CPs post re-build, then there will be increased oil consumption based on tolerances if I recall correctly.
As far as the increased metal I fear you will be chasing your tail for months to come based on your previous post about checking the oil so I don't see a resolution on the horizon, just endless postulating.
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Originally posted by Arith2 View Post
According to that spec sheet, there is a .035 difference from piston size to bore under stock conditions. currently my bore was honed to 87.25 and used CP pistons of same diameter. If there is a .0035 gap clearance now, wouldnt that mean my tolerance is tighter than before?
I’m not sure of the actual measurement my bore came out to be, however I will reach out to see if I can get that.
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Originally posted by Chanman1029 View Post
Thanks for that info, I do have a question about it though bc I’m confused.
According to that spec sheet, there is a .035 difference from piston size to bore under stock conditions. currently my bore was honed to 87.25 and used CP pistons of same diameter. If there is a .0035 gap clearance now, wouldnt that mean my tolerance is tighter than before?
I’m not sure of the actual measurement my bore came out to be, however I will reach out to see if I can get that.2002 Topasblau M3 - Coupe - 6MT - Karbonius CSL Airbox - MSS54HP Conversion - Kassel MAP - SSV1 - HJS - PCS Tune - Beisan - MK60 Swap - ZCP Rack - Nogaros - AutoSolutions - 996 Brembos - Slon - CMP - VinceBar - Koni - Eibach - BlueBus - Journal
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Ok, here it is. All the pictures are labeled which cylinder they belong to. Cylinders 1,4,5, and 6 all seem to have these wide dark spots of marking, while the other cylinders have small vertical scratch like markings. It is hard for me to tell whether those vertical markings are normal, or if they are problems during ring assembly.
Cylinder 5 is by far the worst, and even has what looks like multiple spots of corrosion on the cylinder wall. This alone was pretty disturbing for me to find.
George Hill what do you think about these marks? mind shedding some light on if this is acceptable work by lang?
EDIT: looks like the file names didnt upload:
Cylinder 1: pics 1-3
Cylinder 2: pics 4-5
Cylinder 3: pics 6-7
Cylinder 4: pics 8-10
Cylinder 5: pics 11-15
Cylinder 6: pics 16-21Last edited by Chanman1029; 05-15-2023, 09:02 PM.
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Originally posted by Slideways View Post
this is my first time ever really inspecting a cylinder wall, and although these marks do look abnormal, I just simply am not educated enough to know if they are acceptable or not. The corrosion is pretty much not ok with me. But as far as those wide dark marks go, I just dont know if those are some normal operations or not.
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Originally posted by Icecream View Post
How did you break in the engine?
I did the first start up, let it idle to operating temp. Shut down, let it cool completely, then drove 1139 miles, never went above 4k rpm, and never gave it any considerable throttle until probably 500-600 miles in. At no point during the break in did I drive it hard.
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Originally posted by Chanman1029 View Post
Used 15w-50 conventional break in oil, with zinc. This oil was Langs, recommendation.
I did the first start up, let it idle to operating temp. Shut down, let it cool completely, then drove 1139 miles, never went above 4k rpm, and never gave it any considerable throttle until probably 500-600 miles in. At no point during the break in did I drive it hard.
Not a master at this but I have heard not to use high zinc or anything like that and hopefully you weren't spending too much time at the same/low rpms. Are you getting driveability problems?
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