Cylinder leakdown higher after engine rebuild?

[tlow98]

It’s tough. There are a lot of variables. Get the facts, go from there.

[Chanman1029]

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?

[Arith2]

The bore is 87mm and the stock pistons are 86.965mm. I'm still looking for the spec sheet but I have this so far.

[jet_dogg]

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.

[Arith2]

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.

Yeah forged pistons need to have bigger tolerances simply for the expansion so I guess stock tolerances aren't that relevant in that case. Specs could help someone else though.

Found the specs

[Chanman1029]

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.

Yeah everything was stock prior to the rebuild. Is your comment about the metal just simply because of the amount of metal lingering in the oil will take many oil changes to flush out?

[Chanman1029]

Yeah forged pistons need to have bigger tolerances simply for the expansion so I guess stock tolerances aren't that relevant in that case. Specs could help someone else though.

Found the specs

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.

[heinzboehmer]

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.

mm vs inches

[Chanman1029]

Just got the bore scope, I’m seeing some things, and what I’m seeing definitely doesn’t seem normal…

I will post pictures soon once I go to the store to get an SD card for the bore scope.

[Chanman1029]

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 16-21

[Slideways]

Yeah, you might want to have Lang take a look at those pictures. There are a few S54 disassembly videos on youtube that show a stock used block. On those engines, there are some small wear marks towards the top of the cylinders, but no vertical marks like the ones in your pictures.

Skip to 58:00

[Chanman1029]

Yeah, you might want to have Lang take a look at those pictures. There are a few S54 disassembly videos on youtube that show a stock used block. On those engines, there are some small wear marks towards the top of the cylinders, but no vertical marks like the ones in your pictures.

Skip to 58:00

I agree, I think he should see these, however I just kinda want to have idea first of what I’m actually looking at.

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.

[Icecream]

Just got the bore scope, I’m seeing some things, and what I’m seeing definitely doesn’t seem normal…

I will post pictures soon once I go to the store to get an SD card for the bore scope.

How did you break in the engine?

[Chanman1029]

How did you break in the engine?

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.

[Icecream]

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.

I want to see if I can boroscope mine soon. Just rebuilt and did a hard breakin on conventional 5-40.
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?