Fudgey

iTrader: (4)

As some know, i was behind the wheel of my mates skyline at japfest and had a bit of a problem

anyway, we took the enigne out, and got the head off. head looks spot on and the pistons look ok so we think a hone, new set of rings and bearings and jobs a goodun

well, that was until yesterday when i went over and took the pistons out.

piston 1 has a cracked ring land on the inlet side, about 1.5" wide. infact it was in 3 bits and fell out without much hastle. also it looks like the piston skirt has been rubbing on the bore as its quite scored

piston 2 was the same, ring land cracked in the same place, but in 1 piece, bore was not very scored

piston 3, same as 2

piston 4, fook me, it was ok lol!

piston 5 cracked the same as 2, but also the secondary land was cracked, bit between the 2nd compression ring and oil scraper

piston 6, same as 4


soooooooooo

wtf causes them to crack off like that?

and whats with the scoring of cyl 1?

also, how likely is it that it was fucked before i got behind the wheel??



cunts, i knew this was gonna be expensive

COMEDY DAN

Possible faulty batch, detonation causes it sometimes and also badly honed blocks can pick up on the top of the piston and crack the glands off.

Shings

Detonation - on my 2nd series 2 ( Tims old car) I lost pressure on a few of the pots and detted a few pistons and cracked the land on 1 and 2.

Jake

BlueSmoke

Whatever it is, it seems pretty certain that it was nothing to do with you driving it mate so I'd have to seriously reconsider putting any money in!

Eagle

iTrader: (2)

excessive boost pressure ......
look to see where they have actually cracked in relation to the inlet side of the head....

Fudgey

iTrader: (4)

cheers guys, it didnt sounds like it was detting tho. hmm


there was still good pressure tho, 130-150psi across 1,2,3,4,6 and 50psi on 5.

jay, dont worry, i got no money to give him

Fudgey

iTrader: (4)

eagle, if say you look at the top of the piston on the inlet side, it was about 3/4" from the center line on each side, total about 1.5" long but in the miiddle if you get me? lol

Shings

Fudge mine gave resonable compression to be honest so who knows

Jake

Anonymous

Compression means fuck all in a case like that.

Sounds to me like it leaned out and detonated or got too hot and they cracked.

S1 Barkham

My mate owns a 200sx S14a and one of his pistons did exactley the same. Turned out to be the fuel pump on its last legs and wasn't supplying enough fuel and leaned out. Wasn't till he'd just had the new engine in and the fuel pump died. luckily it didn't cost him another engine tho

Eagle

iTrader: (2)

i know pistons crack the land under excessive boost ... as i did all 4 in my rst sudden shock of doing 30 psi poxy amal valve fell apart
if it was detting surely there would there not be other marks on the piston crowns ??

but it was on the inlet side????

smithy20vt

Fudge have you got any pictures of the Pistons??

Tim

iTrader: (1)

incorrect fueling det as always.

Mike Rainbird

iTrader: (3)

Mmmm, it's a Skyline, so a wild stab in the dark would be:

Too much boost combined with too high compression .

Fudgey

iTrader: (4)

Eagle - yes inlet side.

there were NO other marks on the pistons, the crowns looked 100% fine which is why im not sure it was det tbh.

mike, it was only running about 9 or 10 psi i think

pom, not yet mate, didnt have the camera but next time im over ill take some.