anyone know what caused this

[TheProfessor]

i had my engine finally all done and in the car
i drove it for about 70 miles and then it started knocking
upon dissasembly it was found that one the # 5 piston and cylinder were scored really bad and it needs to be rebored, sleeved and a new piston put in

my mechanic doesnt want to cover it under his warrentee he gave me because he said that it happened because i have the aftermarket chip which caused it to over fuel and the cylinder failure

the chip is a stage 2 fastchip and i have 10.5:1 compression with a crane 272 cam and 1.6 roller rockers

could the chip have caused this or is he trying to pull some shit on me and get out of fixing it

what do you guys think

[RednBlack]

Your mechanic is a moron. No way a chip can cause scoring. Has to be bad assembly or bad break in. I think you know that already, from your previous posts.

[TheProfessor]

thats what i thought
thanks bud

[sharkey]

more than likely what heppened is he didnt get the piston-wall clearance right or had the rings gapped to tightly. whatever caused it, it is 100% not because of the chip.

[Doubt_Incarnate]

how are the rings? i know one time i broke one during assembly but didnt know it untill start up, but i suppose that doesnt cover knocking, so i guess he over bored, or maybe the piston went in backwards.

[geoffinbc]

Over fueling can cause scoring. But it would require a ton of fuel to cause that much washing that the exhaust would be all black and the car would run like shit.

[RacerX11]

Could be bad injector overfueling on only one cylinder.

Marty

[Guest]

Either way, it's not the chip.

Also sounds like a too tight wrist pin.

I'd also have a look at the wall clearance and the ring end gap.

[lumination]

overfueling can make your rings take a long time to seat but unless you had 100gph flowing to that cylinder with a fire hose! 70 miles is your mechanics fault If I was you I would drag his lying, lazy @$$ in the parking lot and get my moneys worth if ya know what I mean.

Im new to these v6s but an engine is an engine this sounds like a bored out cylinder and a stock diameter piston or sloppy tolerences on the bore

[TheProfessor]

info update for everyone
heres whats going on
after i had the motor built i drove it home heard the piston noise and took it back
now the engine is dissasembled and i have inspected it
after 140 total miles it has one of the pistons worn away on one side and there is a big gouge in the corrosponding cylinder
the tops of the pistons and the heads (including valves) are covered in a black substance making the engine look like a carboned up motor with like 150000+ miles on it the machine shop guy said when he took off the heads that there was actual liquid gasoline sitting in the piston dishes
the one cylinder that was messed up was alowing gas into the oil as well
i smelled the oil filter and there was some gas in there
now another thing is that the engine ran alright with a little bit of a lope at idle when i got it but nothing crazy like stalling
the ecm also had a lean code stored in it
anyway i hope some of you guys can help me figure this out so i can explain it to my mechanic and get his ass fixing it soon

[geoffinbc]

You need to presure test that injector for leaks. Was the exhaust ever black?

Or it could have been a missing spark on that cylinder causing the lope and the cylinder to flood with gas.

[TheProfessor]

the exhaust was never black
the cam i have causes the lope
ive had a carbed olds 350 before that i actually did over fuel but it was only because the timing was off
it ran all funky, was really hard to start, and backfired and puffed black smoke
my retta with the new engine started and ran fine

[RacerX11]

There was raw fuel puddled in the cylinders, and gas in the oil....no amount of screw-up on the machine shop during assembly can cause this. How do you know it is the cam causing the lope, and not a misfiring cylinder? An engine running pig-rich on all cylinders (like your carbed 350) is going to run like crap...but with only one cylinder running rich due to a bad injector, it probably won't be noticable (other than maybe a lope), and you might not even get any exhaust smoke if is overfueling to the point of misfire. The ECM lean code possibly points this direction as well. If one cylinder is not firing, the unburned oxygen in the exhaust will be read as a lean condition by the O2 sensor, even if the other cylinders are running perfect. I say your problem is with your fuel or ignition system, not your mechanic.

Marty

[TRKK11]

professor, sorry about your problems, that sucks, but i have no idea what to tell you, but how did you come up with 10.5:1 compression?? Thats what i want to run on my new engine, but i cannot figure out how to get it to that.

[geoffinbc]

Custom pistons

Or deck the heads