Piston Failure? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

turbo101 · 02-13-2010, 06:30 PM

I have a redtop sr20det, i took the head off to replace the H/G.
last summer i was running 15 psi on gt2871r, enthalpy tuned.
my timing was off for about 2 weeks, pretty hard detonation...
still ran strong after retimed it to 15 deg. BTDC.
for 3k miles it ran strong, ran 12.6 quarter mile. no smoke, no oil burning.
driving it pretty hard also. my oil catch can did consume oil fairly fast, i thought it was just because i was at the track beating it.
i didnt think to compression check it before i ripped it out.
and now im cleaning my block, noticing damage on 2 pistons.
i have pitures, its just too hard to see it.

My best explanation of the damage would be, on one side its raised, really rough, (80-120 grit sandpaper) but its still round in the clyinder. the sleeve or cylinder wall is rough right where the piston is rough.
The cylinder wall doesnt seem too bad. its just rough at the corner of the wall and the top of the block.
I dont have the tools to compress the rings, and im scared to take it all out. I dont have any measurement tools or any of that stuff, let alone a trustworthy machine shop.

what should i do?

(pics came up on nico) http://forums.nicoclub.com/zerothread?id=478065

*fliprayzin240sx* · 02-13-2010, 07:55 PM

http://c2.ac-images.myspacecdn.com/i...51ec42edc5.jpg

Seen those numerous times. Usual sign that the engine was leaning out and started melting the block. Best bet is to deck the block down to clean it up and run a thicker headgasket.

turbo101 · 02-14-2010, 08:03 AM

would a apex-i 1.1mm H/G work? thats what i have.
im thinking i can just pull it apart get it machined, buy two new oem pistons, rings, bearings and be done with it?

***S14DB*** · 02-14-2010, 08:22 AM

Looks like pre-ignition. How much carbon buildup on the head?

More then likely from all your detonation from bad timing.

turbo101 · 02-14-2010, 08:55 AM

Quote:

Originally Posted by S14DB

Looks like pre-ignition. How much carbon buildup on the head?

More then likely from all your detonation from bad timing.

Yes thats what i have been thinking. the carbon buildup isnt too bad, but idk whats bad or not, i can take a pic if youd like to fill me in

i just dont understand why the engine ran perfect.. i hope it doesnt need bored, i cant afford anything but 55$ oem pistons

THank you for the help!!!

02-13-2010, 06:30 PM	#1
turbo101 Join Date: May 2008 Location: iowa Age: 37 Posts: 24 Trader Rating: (0) Feedback Score: 0 reviews	Piston Failure? I have a redtop sr20det, i took the head off to replace the H/G. last summer i was running 15 psi on gt2871r, enthalpy tuned. my timing was off for about 2 weeks, pretty hard detonation... still ran strong after retimed it to 15 deg. BTDC. for 3k miles it ran strong, ran 12.6 quarter mile. no smoke, no oil burning. driving it pretty hard also. my oil catch can did consume oil fairly fast, i thought it was just because i was at the track beating it. i didnt think to compression check it before i ripped it out. and now im cleaning my block, noticing damage on 2 pistons. i have pitures, its just too hard to see it. My best explanation of the damage would be, on one side its raised, really rough, (80-120 grit sandpaper) but its still round in the clyinder. the sleeve or cylinder wall is rough right where the piston is rough. The cylinder wall doesnt seem too bad. its just rough at the corner of the wall and the top of the block. I dont have the tools to compress the rings, and im scared to take it all out. I dont have any measurement tools or any of that stuff, let alone a trustworthy machine shop. what should i do? (pics came up on nico) http://forums.nicoclub.com/zerothread?id=478065 Last edited by turbo101; 02-13-2010 at 06:36 PM.. Reason: mistakes

02-13-2010, 07:55 PM	#2
fliprayzin240sx Man w/ CTSV & a Car Seat Join Date: Aug 2002 Location: Tampa Posts: 17,998 Trader Rating: (19) Rides Gallery: fliprayzin240sx Feedback Score: 19 reviews	http://c2.ac-images.myspacecdn.com/i...51ec42edc5.jpg Seen those numerous times. Usual sign that the engine was leaning out and started melting the block. Best bet is to deck the block down to clean it up and run a thicker headgasket. __________________ If you think Zilvia has too many assholes... CLICK HERE!!!

02-14-2010, 08:22 AM	#4
*S14DB* AFC #1 Join Date: Oct 2003 Location: 昨晩あなたのお母さんの家 Posts: 20,181 Trader Rating: (3) Feedback Score: 3 reviews	Looks like pre-ignition. How much carbon buildup on the head? More then likely from all your detonation from bad timing. __________________ Comments should be taken as Opinions not as Statements of Fact

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02-14-2010, 08:03 AM	#3
turbo101 Join Date: May 2008 Location: iowa Age: 37 Posts: 24 Trader Rating: (0) Feedback Score: 0 reviews	would a apex-i 1.1mm H/G work? thats what i have. im thinking i can just pull it apart get it machined, buy two new oem pistons, rings, bearings and be done with it?