Robert AMG

iTrader: (1)

I need help, i am running with the M112 V6 350 2004 with 3.72L block, with C32 AMG crank, cams and oil pump, N/A 55 AMG pistons 2003 which made my static compression ratio at 8.5:1(2mm lower), so i have a low compression built, plus the 55K supercharger on the engine which made 20-22 psi boost on stock pulleys and a lot of cooling.
The car was running good and made 450-470whp, but after 1000miles the oil was going out from the heads.
so i found a one side of the engine with low cranking compression(90-100psi) and the other side is good(160-170psi)
i looked and found a bad crank pulley install, missed key so the timing chain was installed wrong, and today we took the engine apart and found the 3 pistons at this same side with land failure and valves hitting pistons, but the other side of the engine without any issues, pistons are good.
so my question is:
the pistons(N/A) land failed because they cannot handle the boost or the timing on one side is so high because of the wrong timing chain?
thanks.

AMGPilot

Land failure us usually from too much timing

e55amgrocket

Ring lands fail because of heat 99% of the time. If your tune is really fat then you could also push fuel past the 1st ring and get it caught by the 2nd ring and boom. Blows the ring land. The biggest cause is asking for to much from the pistons we have. They just weren't designed to deal with 22psi. Does it look like the rings might of pinched possibly? Do you know why your ring gaps were? If your staying with stock pistons I would open the top ring a tiny bit to around .030 and and make sure the 2nd ring is wider than the top ring. The 2nd ring is to help control oil and mostly control heat. If your pulling pistons out replace them with good forged pistons and a good ring package. Might be a good idea to have them anodized also for the boost your running.

benz_addict

too much timing. same thing happened to my 55 motor, a tooth off

e55amgrocket

What was your AFR and timing at? I'd be willing to bet it was way too rich. Being off a tooth sure Didnt help you any either.

Robert AMG

iTrader: (1)

Thanks, the rings look good, i didn't gap them before, those pistons are light weight(55k=582grams, those 55n/a 2003=532g) and have thinner rings, the upper and lower lands failed. My purpose is to put a bigger pulley so i might be at 25-27psi, where i can find custom forged pistons?
but if the pistons didn't hold the boost why they failed on one side only?

Robert AMG

iTrader: (1)

my AFR was rich, timing 18-20.

e55amgrocket

How rich?

Robert AMG

iTrader: (1)

what was confusing me is that my wideband was always on the side of the engine that didn't failed by coincidence, so i didn't know what was happening at the failed side and i didn't know that i have a problem till now, and i did a lot of tunes afr was between 10 and 12 after 4000rpm but at low rpm it was lean 15-16.

Robert AMG

iTrader: (1)

always friends saw black smoke from my exhaust, i was confused as i look to my wideband and it was ok.

e55amgrocket

Looks like that side was really rich. Anytime AFR is way down in the 10's your asking or trouble. On a good piston with a wider gap it wouldn't be as bad. You need to log both sides for AFR also.

Robert AMG

iTrader: (1)

so you'r saying if afr very rich it may be pushing fuel past first ring a blow the land.

Gadget

Cam timing is very important. If it is way off like you described it can cause a lot of problems. If the failures were on the side that the cam timing was way off that could be the cause.

G

e55amgrocket

Pretty much any piston company can make you whatever you want.

Dominic2

Call Probe Pistons. Ask for Mark, he is the owner. If he gives you any **** tell him that you were referred by yellowbullet.com.

e55amgrocket

Mahle has forged SLR pistons and I'm sure could make what you need based off those. I prefer Diamond myself and have used them in every engine I've had and never had a problem. The rep I deal with is Mike. 2 week turn around too.

GT-ER

I'm sure your cam timing issue had more to do with it than anything else since it was on that side ( too much coincidence ). Small ring gaps can also break ring lands when the heat goes up. Also, hypereutectic pistons are somewhat brittle and, while they are stronger than cast pistons, any amount of detonation can crack their ring lands.

Yacht Master

+ 1. Detonation, yes the hypereutectic pistons are the weakest link and the N/A 55 more so. Don't think you could use 55k pistons because it might drop your compression even lower with your -2mm crank. The pulley issue is pretty common, and once they come loose the key can shatter, same key to oil pump and cam drive sprockets. Hope you get it all sorted out. Post some pics, I find it interesting the v8 kompressor on a v6.