existanzcivicb20

Please notice the pitting on the flat part of the combustion chamber What would cause this and only on cylinder #3 all others look good? Also seems to be burning oil in that cylinder
Set up is a B20 block with weisco pistons 14:1 compression the head is a GSR with all skunk 2 pro series parts let me know if u need more info

PyroProblem

how do your valve seals look? Not smashed?

existanzcivicb20

No not at all

PyroProblem

Oil can really only get in the chamber via passed valve stem seals or rings. If your sure the valve stem seals are good to go, might be time to pop out #3 piston and see if anything looks abnormal.

You have a crankcase vent system setup? Venting block pressure and not recirculating oil vapor/block pressure back into the intake? That's all I can think of...

Those nicks in the chamber on the flats. Previous damage? Do the other cylinders have the same marks?

DDTECH

Look at the head really good, its talking to you.

The oil soot is heavier on the intake side. Your Valve seals on the intake are leaking, pretty bad too according to that plug. It could be a ring issue, but if the rings were clocked correctly and installed correctly with a good, straight hone and the cyl is straight, i dont see that being a ring issue.

Whats the exhaust ports on the head look like, thats a pretty good sign as well


Also , what pryo side?.. Is that piece of the HG rubbing still on the head or actual nicks.

existanzcivicb20

Yes the issue I am talking about is the pitting of the combustion chamber on the the flat is what I am worried about. I did get all new valve seals and all new piston rings but before I put it all back together I wanted to know of what would cause the pitting.

PyroProblem

Looks like something got in there and bounced around for a second before probably making its way through the exhaust.
Could possibly be from running an open intake and picking up a pebble or something. All your throttle body blade screws still in place?

existanzcivicb20

Haven't really looked into that but the only time there was no air filter was when I was running it for the first time inside my garage never took it out on the street. But my throttle biddy was brand new so I'll inspect it and look for missing pieces

98vtec

Considering your compression and not telling us what gas/octane, that would be very useful information. As well as any tuning data you can tell us about as far as ignition timing and fuel.

How do you know for sure you are 14:1? (Beyond having "14:1" pistons)

whitesihatch

x2,

also are all the valve guides in tact? Ive seen scenarios where a tiny amount broke free for whatever reason and caused pitting like this, the tiny shard would bounce around, eventually making its way out of the exhaust.

existanzcivicb20

93 octane and I took the head apart replaced the valve guides ( even though they appeared to be damage free) I inspected the valve guides as much as I could and they also appeared to be fine. The running was done by a buddy of mine I'll ask the details.

98vtec

I think you just answered your question.

pre-ignition will kill an engine with the quickness.

pretty much any knowledgeable tuner would have declined tuning your "hot" engine with fuel that will not meet its requirements.

I would strongly consider rethinking your build strategy

MUGEN GUY

iTrader: (6)

YIKESS 14:1 on 93

existanzcivicb20

Then I might be mistaken I bought the Pistons About a year ago and that's when it got tunes so now I'm unsure if they were 12:1 or 14:1 but now that I think about it 12:1 does sound more reasonable and I know we tested it and I wrote it down so now I have to dig through my sh*t and I'll update

jimmysxxl

since it's #3 only, i also agree with everything already been said, It's pre-ignition that did that.

93egSLEEPER

Who built this motor? Was it clayed and clearanced when put together? If it truly is 14:1 motor this isn't a plug and play motor you throw together and tune on pump gas. Judging by the story and info you're giving, that is what happened.

What cams are you running? You can use a long duration cam to bleed off some compression, but depending on the piston domes you need to be careful unless it's been clearanced/clayed. Can you post up pics of the pistons or do you have part numbers?

No offense, but this build seems like it was a mistake from the beginning. To much unknown and very small thought process.

DDTECH

Doesn't matter who tunes it, 93 isn't enough octance for 14. I actually had a customer run into a similar issue in which the compression was mis-understood. The end result was not pretty.

whitesihatch

LOL, like others have said, this kind of setup cannot be slapped together. There are a lot of important factors that dictate tolerances. Something so simple as ambient temperature will determine the ideal viscosity of the oil, which determines the best possible clearances, not to mention the duty and speed of the motor. Fuel, was definitely overlooked here.

Build your motor based on cam profiles and fuels easily obtainable.

PyroProblem

I've seen detonation marks on the tops of pistons before. Can the same marks so be found on cylinder heads?