I usually find something to help with my problem on this site in a search...not this time. My 6.5 felt like a gas engine running on 7 cylinders, like I was dragging one...lots of shaking. Also lots of diesel fuel smell, like raw fuel was being passed through the cylinders and out the exhaust. We pulled the heads last night and this is the condition of the number one piston. I have never seen a pattern like that, its like the outer edge was masked off and steam cleaned. Any suggestions on what caused this? We are pulling the block today, '94 300K miles its time for a re- bore and new heads, but what caused this pattern?

Thanks

69908

looks like it may have hit the head, can u post a pic of the head also?

looks like it may have hit the head, can u post a pic of the head also?

I agree. seen it on gassers with a lot of miles. it was the result of a couple of things in different engines. wrist pin worn out, wrist pin hole in piston ovaled, crank bearing missing/worn out. once you get into the lower end the problem will probably be revealled.

Do the rest of the pistons look normal?

Are the injectors still in the heads or do you know which one came from that cylinder? Thinking maybe that injector stuck open and started washing the cylinder. That outer ring is where it was machined off, so it would clean off faster than the cast textured portion of the piston.

Look at the tips of your injectors, they all should look like dry black carbon. If you have one that is damp/wet, take it apart and see if the needle will slide out easily. If it was stuck open there might still be fuel in the precup on your bad cylinder.

I think you would have had alot of blowby if your piston was bad.

The top and some of the side is anodized. The outer top has been machined away per GM. That's your "taped" area showing.

How was your injector #1? May be it was leaking so much that your piston has been washed by excees of fuel...

Here is a pic of the head. I don't think the piston kissed the head, not a scratch and there was no unusual noise, just running rough. I think the leaky injector is the reason, I heard a very light knocking that started about two months ago and pulled the injectors out and had them tested. The shop that tested them said they were fine. I put them back in and now this. I will no more tonight when I get into the bottom end. Thanks everyone



69926

Looks to be in nice shape for a 300,000 mile engine. Altho, i'm used to what it looks like inside 30 year old gas engines. They look a hell of a lot worse than this engine does!

very nice for 300k

I agree looks nice for that many miles. That cylinder looks fuel saturated probably is/was injector problem. Not sure if I wouldn’t put it back together with new injectors and see what happens. All my experience has been with gassers.

I usually find something to help with my problem on this site in a search...not this time. My 6.5 felt like a gas engine running on 7 cylinders, like I was dragging one...lots of shaking. Also lots of diesel fuel smell, like raw fuel was being passed through the cylinders and out the exhaust. We pulled the heads last night and this is the condition of the number one piston. I have never seen a pattern like that, its like the outer edge was masked off and steam cleaned. Any suggestions on what caused this? We are pulling the block today, '94 300K miles its time for a re- bore and new heads, but what caused this pattern?

Thanks

69908is it my imagination or has that gasket been sweating there on the affected piston area?

I agree looks nice for that many miles. That cylinder looks fuel saturated probably is/was injector problem. Not sure if I wouldn’t put it back together with new injectors and see what happens. All my experience has been with gassers.


:agreed:, What he said,

That engine looks good, I couldn't even see any cracks between the valves(the ones off my 93 you couldn't miss in that pic, but still held water). How much oil was it using/blowby, if minimal I'd stick the heads back on and run it, if that injector turns out to be bad.

I figured out what happen to that cylinder. The clip that holds the No. 1 cylinder intake lifter together snapped off and the top of the lifter was pushed next to the push rod. One picture shows the top of the lifter and push rod and the other shows the fit after about 15 miles. There was not enough oxygen to allow for proper ignition and the cylinder was filling up with fuel...and just dragging. I am still going to rebore/rebuild, because if I just replace the lifter and push rod something else will happen break next week, and I will wish I did. I have been wanting to put a lower compression piston in anyway for higher boost pressure.




69947

69948

I dont understand why people want to lower the compression ratio. Would the extra boost you are able to make with lower compression make up for the said lost compression??

Ouch. Was the plastic rocker arm keeper still on that valve?

Yea, nows a good time to do a full build, if wanting 18:1. I want to build an 18:1 engine for my 93, but haven't had the excuse(wife) or the time to do it, just gonna wait till it breaks, it runs pretty good as is.