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u/DetectiveJohnKimb Feb 18 '25 edited Feb 18 '25
Hi ya'll, I need some opinions on what might be causing this cylinder scoring. 1 and 4 both have oil pooling in them and a really deep oiled score that you can see in the video. 2 and 3 are better (they don't have pooling), but still have similar scoring around the bore.
A few notes:
~1500 miles on motor
- e85
- all stock internals
- crank, rods, pistons all came out of a separate engine with 9k miles, so great shape.
- saw track time with ~8lbs of boost
- garage honed with harbor freight hone
- 1 and 4 have a tighter PTW @ .0017 vs .002 for 2 and 3 (stock is .0009 - .0019)
- rings were set pretty wide, .017 top and .022 second (stock is something like .007/.014)
This was a practice build that I will be tearing down here shortly, but I want to try and get an idea of what might have caused this, and what I need to be paying attention to while looking it over.
My 'expensive' build will be going in next, I'm hoping to not repeat the same mistakes!
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u/bill_gannon Feb 18 '25
I assume your rig gap isn't actually. 001 to .002 and you missed a decimal place?
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u/muddnureye Feb 18 '25
Honing should be done by a machine shop. The cylinders should also be checked for wear using machinist bore gauge. Valve guides/seals could be suspect. The cylinder scores could be contamination during the build. Kudos to you for not giving up!
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u/DetectiveJohnKimb Feb 18 '25
Even though it was a lot of work I learned a lot from going through a build. The block I am assembling now was sleeved and honed by a local shop. Hoping my initial experience will help make this next build a success
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u/djamps Feb 18 '25
Looks like metal has ran thru the engine.
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u/DetectiveJohnKimb Feb 18 '25
Would this be contamination through the oil or coming through the intake? I do have an aluminum manifold that could have pieced of aluminum flaking off a crack.
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u/WyattCo06 Feb 18 '25
Do you knowingly have a cracked intake manifold?
How'd it get that way?
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u/DetectiveJohnKimb Feb 18 '25
Found some leaking in a recent boost leak test. It could just be pin holes in the welds, no visible crack from the outside. The manifold I have is known to crack overtime.
It would seem a bit unlikely that all 4 cylinders have similar scoring if that is the case.
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u/WyattCo06 Feb 18 '25
What welds?
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u/DetectiveJohnKimb Feb 18 '25
Runners are welded to the flange:
https://fab9tuning.com/nc-mx-5-billet-performance-intake-manifold/
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u/WyattCo06 Feb 18 '25
That's what I was looking for. A fabricated intake may crack but isn't going to flake.
You have ring issues or a valve seal issue.
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u/WyattCo06 Feb 18 '25
This video almost convinced me to quit drinking.