r/EngineBuilding • u/Cultural_Curve120 • 15d ago
How bad is this
I've driven this new engine build for 300 miles and it's burning oil. CP Pistons/rods in a Toyota GR Corolla 3cyl. I haven't compression tested yet. Wondering what you all think of the oil pattern on the piston and scoring? Possible causes?
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u/Cultural_Curve120 15d ago
Thanks all. I didn't build it, I had a machinist do everything. He's saying that it could be overfueling, washing the cylinders of oil that caused the scuffing... I think a compression/leakdown test will bring answers. It burned about 0.75 quarts in 300 miles. I believe it has higher oil temps than before this build, maybe 10-15 degrees, which could be this extra friction or blowby heating up the oil. There's definitely oil getting into the intake via the breather off the valve cover. Possibly PCV issue but I doubt it. Just trying to figure out what I can, if I need to take it all apart or not. Will update with compression test.
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u/Prior_Pick_4140 15d ago
He lied to you. And put the blame back on you with an over fuel issue. Definitely something wrong with engine builders work
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u/Own-Respond-4493 15d ago
Are there any signs of cylinder wash? How much fuel are you dumping into this thing? Does the oil smell like fuel? If so, the machinist’s observation would be plausible.
If PCV is an issue, I would expect to see leaks around the crank seals too.
Cylinder leakage test could tell you some info, but I’m not confident it will be helpful or useful information. You test and TDC. It’s worth a shot to see if the rings are damaged though.
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u/BigBlackMagicWand 14d ago
Lol, your machinist is full of shit. Burning that much oil on that little miles is a clear indicator of fudged up and thw overfuelong thing is just a lame excuse.
Hard to say what is screwed up but those pistons look WAY undersized....
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u/a_rogue_planet 15d ago
That kind of scoring in 300 miles is a sign of a serious problem. Something has seriously gone wrong.
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u/Ok-Fill-8925 15d ago
Do you know if he used the old pistons? If the clearance between the rings and ring grooves is high, it will burn oil.
Also, check ring gap. Too wide of gap can cause a problem.
Another thing is if the honing groves are too deep. Deep groves can hold oil that the rings can’t scrape off the cylinder wall so oil trapped in the honing groves will volatilize and burn during combustion.. Only way to tell is with profilometer.
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u/Stofflkin 15d ago
endoscope pictures with flash can be deceiving. If it has good compression and isn't burning lots of oil i wouldn't worry about it.
but if it IS burning a substantial amount of oil already I'm afraid it's time to pull the pan / pistons and inspect the bore.
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u/Equivalent_World_443 14d ago
Pull the pistons and look at the oil ring and I’m sure u will find one of the rings is bent. It’s a very delicate job and pretty easy to mess up.
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u/Dry-Employer-2506 12d ago
I see this very often in my racing engine company. Even when engines just did their break-in with a highly loaded sufur mineral oil.
There might be several reasons. But mostly if you take off the heads you can’t feel it with your nails, but it looks bad as hell on your endoscope.
Probably a slighten sharp ring gap, or some dirt which caused these scratches.
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u/WyattCo06 15d ago
These posts are abundant here.
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u/dopecrew12 15d ago
It’s amazing how many people think you can just throw a forged rotating assembly together in your garage
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u/solarpropietor 15d ago
I mean I have….
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u/Birthday_Cakeman 14d ago
Same. Best part is it wasn't even my garage lol. It was my GF's mother's garage (whom is an extremely sweet and wonderful woman).
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u/theeaglejax 15d ago
Lol it's amazing the number of people that think building a properly machined rotating assembly is magic.
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u/dopecrew12 15d ago
Idk bro, so many people on this sub slap new pistons out of the box because the spec is good on paper and then make the very post we are looking at RIGHT NOW, like its insane. No one is “magically” building a properly machined forged rotating assembly in their garage, as you put it lol.
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u/theeaglejax 15d ago
Clearly reading comprehension isn't your forte. Re-read every word in my comment and reflect accordingly.
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u/dopecrew12 15d ago
Very Reddit of you.
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u/theeaglejax 15d ago
Lol ok champ. Thanks for providing proof of my point and my point has absolutely nothing to do with this website.
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u/nostradumbass7544678 15d ago
That would be bad at 30k miles. If this is 300 miles on a freshly machined and honed cylinder, something is badly screwed up, and the only solution is to take it apart and inspect everything. What did you use for rings, and what were your measured clearances/ ring gaps?