jeffp Posted December 30, 2006 Share Posted December 30, 2006 The pistons were damaged from FOD, with the engine is running you would have seen a different type of marking, less defined then what you have there. The coating doesnot seem to last as well as some would believe looking at your pistons. I have always thought it was a waste of time for any engine that was not full race setup, and freshened frequently, but to eaches own I guess. I did notice the skirt and see that all to familiar scuffing, scratches and darkness of the skirt. That is due to the piston expansion in the bore, you need anywhere from .0005-.001 additional clearance to allow the piston to expand in the bore. How hot did you engine get at any one time? I had problems when the engine got hot one day almost full gauge reading, to hot, but what do you do when the engine gets that hot in the middle of nowhere, shut it down, I was afraid it would freeze up. So for this next build, give the pistons some additional clearance, forget the coating(waste of money long term) and try it again. You can call Robello racing, and they have a new bearing that is really good, and it is coated as well. Since you will need at least a polish of the crank journals, this would be a good time to get that type of bearing. I spoke to dave at length regarding the bearings, and he said they are tougher then nails, in fact he has reused these parts in builds, because they are so durable, much better then the Cleveite bearings everyone myself included, uses for extreme duty operation. Believe me I feel your pain, that is going to cost you for that fix. Quote Link to comment Share on other sites More sharing options...
240hoke Posted December 30, 2006 Author Share Posted December 30, 2006 Well thanks for the replies again. I will report on the other skirts and bearings in a few, I am about to go tear the rest down. JeffP Thanks for the advice. The pistons however were coated on the sides from JE, a teflon like coating. Thats why they are dark and the scratches actually look alot worse then they really are. I kinda got stuck with these pistons, I didnt pay any extra for the ceramic but I was disspointed to see that it only lasted a couple thousand miles non the less. Right now I just cant justify spending the money on rebuilding this motor (nor do I have the money right now) So more then likely ill be sanding the ridges off the piston and head and installing some new bearings.... and turning the boost up screw it. Quote Link to comment Share on other sites More sharing options...
slownrusty Posted December 30, 2006 Share Posted December 30, 2006 Austin - Man...I am sorry to hear about the damage...I feel for you bro, I think quite a few of us have been down this road and it sucks! One thing that puzzles me, if the damage was caused by something foreign, why are all the damage marks exactly the same size shape, you think if it was slag, it would get more and more irregular as it was getting pounded up inside the engine? From your pics it looks like it bounced up and down 30+ times, wouldn't it slowly disintegrate as it kept bouncing? JeffP - can you tell us more about these bearings that Dave is recommending, and price? I am rebuilding my L right now and will be ordering Clevites but can hold off. I am subscibing as there is some very interest content being shared. Austin - when you turned up your timing at SEZ, what kind of AFR were you registering out of curiousity? Makes you woner if you should have dedicated gauge and reading on number 5 and 6? Hang in there, you have the right attitude! Regards - Yasin Quote Link to comment Share on other sites More sharing options...
240hoke Posted December 30, 2006 Author Share Posted December 30, 2006 OKay got all the pistons out, inspected everything. Block has no damage, no scoring on the walls at all. Also no damage to the crank. The bearing damage is worst on #6 with some light damage to number #5. The rest looked pretty normal, with wear I would expect. Top compression rings are stuck in all but one piston, they can be removed but takes a a little force, #6 is by far the worst. Scoring is limited to #5 and #6, with light scoring on 5. Its not really deep though, I cant feel the marks with my fingers but can catch them a little on #6 with my nail. I cant see any damage to the valves everything seems to seal and open and close find. Good bit of carbon buildup though so if this happened during the initial startup the marks could be covered up. I have pretty much rulled out welding slag, I checked my I/C pipes which have two welds total both of which I can see and they are very clean as I expected (I had cleaned them numerous times) But I guess its still a possibility. Whatever it was it doesnt matter, shes going back together since the only un repairable damage seems to be the dimples which I think I can clean up just fine. Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted December 30, 2006 Share Posted December 30, 2006 Pistons ande head = aluminum, FOD = iron or steel. I don't think aluminum will deform iron or steel at the speeds we're talking about.... Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted December 31, 2006 Share Posted December 31, 2006 Try not to use sand paper or any other sanding type abrasive on the pistons or the head, instead use a super fine stone such as a small Arkansas wet stone for sharpening knives. Using the stone will allow you to much more accurately correct the surface's and will not put any loose abrasive grit inside your engine. I did some digging around and found a picture of the stone kit that I use. Which is located here: http://www.ind.nortonabrasives.com/Lineart/ShowLineArt.asp?catID=175 Dragonfly Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 31, 2006 Share Posted December 31, 2006 I counted 59 dings on the piston. That was on the edge of the piston so who knows how long it just bounced around in there. I am guessing it was in there for a long time. something could have gotten in your BOV since it does not have an air cleaner. Quote Link to comment Share on other sites More sharing options...
jt1 Posted December 31, 2006 Share Posted December 31, 2006 Looks to me like a little ball of weld metal from the IC, manifold, or piping. How does the ceramic coating on the other pistons look? The top rings being stuck makes me think of detonation collapsing the piston crown down on the rings. Check the lands very carefully. John Quote Link to comment Share on other sites More sharing options...
JustinOlson Posted December 31, 2006 Share Posted December 31, 2006 Couldn't you just order a single piston from JE? Justin Quote Link to comment Share on other sites More sharing options...
bubbleguinea Posted December 31, 2006 Share Posted December 31, 2006 man austin thats horrible...i know how it feels to have to go through an engine, heheheheh.....imagine how i felt when i pulled the head to find three holes in the top of #4 piston, and a missing valve head (jammed in the head CC) <- and to think i drove it home 9 miles...it was making horrible racket, but she still drove !!! dont mean to be an ass...but maybe someone doesnt like you??? it wouldnt be to hard to plant some small bbs or ball bearings in someones intake tract.... Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 31, 2006 Share Posted December 31, 2006 I think Austin leaves the car in a secure locked garage...sabotage should not be a problem... It definitely looks like a high carbon steel ball bearing. An aluminium ball from the IC would be very soft 2xxx-3xxx series aluminum and would smush after a few times around in the piston. Quote Link to comment Share on other sites More sharing options...
bubbleguinea Posted December 31, 2006 Share Posted December 31, 2006 its wierd...the spots arent perfectly round either...but i guess thats just because of it boucning around in something moving at 5000+rpm..... huh.... Quote Link to comment Share on other sites More sharing options...
240hoke Posted January 1, 2007 Author Share Posted January 1, 2007 Hey guys, Well yall are prolly going to think that I am ghetto. And I have a few confessions to make. Four of the pistons had stuck top rings. I was able to lightly heat them up and slide the rings out just fine with no damage. I looked very closely and and I do have some detonation damage. You can see it on the head, light spongie area arround the edge of the combustion chamber particularly in #5. It can also be seen as well one a few areas around the pistons right above the top compression ring. Its not very bad though at all though but its there. I know that I was detonating a little at SEZ and before due to my large timing advance. I couldnt hear it though because I was running an open wastegate. IT sounds cool and all but its overall a bad idea. I wasnt detonating bad but when I plumbed my wg back in I caught it and ended it quick. I got a new set of rod bearings, and I used a very fine and small file to smooth out all the dimples from the FOD. I then polished it a bit with fine sand paper, then cleaned everythign very well. Then for the top land I took the fine sandpaper folded it up and ran it around the gap a couple times. Worked perfect. Im in the middle of putting everythign back together now. I dont see any reason why it wont work fine. I have a strong feeling like the FOD was done when I first built the motor over a year ago anyway I will post some pictures of the detonation damage tonight, if i can take a picture it might no show up very well. Quote Link to comment Share on other sites More sharing options...
phil280zxt Posted January 1, 2007 Share Posted January 1, 2007 I just find it amazing that something could withstand that punishment and retain its perfect round shape. Also amazing is the pattern of the dimples on the top of piston #6 matches the dimples on the head exactly. Goes to show you how little the tolerances are in an operating engine!! Quote Link to comment Share on other sites More sharing options...
Guest larstw Posted January 1, 2007 Share Posted January 1, 2007 Hi I have seen exactly the same damage for some years ago in my Skyline racecar - the japanese Nismo mechanic called it high speed knocking. Detonation which you have no possibility to hear, due to it to occur in high revs only. In opposition to the ordinary "torque" related knocking. But he was absolutely sure. And as far as I remember it looked all the same as your damage. Quote Link to comment Share on other sites More sharing options...
240hoke Posted January 1, 2007 Author Share Posted January 1, 2007 Interesting perhaps that is what it is. One thing that confuses me about it being FOD is that it is on the "uphill" drivers side of the motor.... which seems very odd, if it occured curing cranking etc I would think that the particle would have moved downward and rested on the downhill side. If it was at high speed I think it would have messed up the turbo. So maybe its not FOD at all sure looks like it though. Regardless hopefully Ive got things right now as far as timing, i know my fuel has always been fine. Quote Link to comment Share on other sites More sharing options...
240hoke Posted January 1, 2007 Author Share Posted January 1, 2007 Here is what I believe might be some detonation damage. Piston damage was to small to take pictures of. #4 #5 Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted January 1, 2007 Share Posted January 1, 2007 I am thinking the FOD spent 95+% of the time bouncing around in the dish of your piston and very little time squeezed between the raised part of the piston and head. Austin, who did the welding on your head? it looks pretty good... Quote Link to comment Share on other sites More sharing options...
240hoke Posted January 1, 2007 Author Share Posted January 1, 2007 No welding, what are you talkin about? Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted January 1, 2007 Share Posted January 1, 2007 your running a P90 head right? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.