Contour Enthusiasts Group Archives Forums Modifications Forced Induction Question on detonation ...broken ring land

I have diamond pistons and I had a cylinder go down on me so I removed the piston to find a the ring land between the top ring and second ring was cracked in two places an inch apart. I am not sure as to what have may caused the piston to fail. I do have an EGT and never saw it blink caution which is set at 900 celcius. I am sure the piston need to be replaced for sure. I had no scarring in the walls because the land did not break off just cracked allowing the gas to go down the rings and into my oil. I am puzzled on the fact that all pistons have a shinny sandy feeling on the intake side of the corner of the piston. I noticed this on all pistons so is this normal in forced induction side to have a hot side of the piston. I know that the ring land crack was on the opposite side of the hot side (sandy pitty surface)
So if this abrasive surface is sign of pinging does this mean my piston are no longer strong and good?

Now I will say all my other cylinder are up to par on my leak down tester.

I hoping to just get another piston and new rings and hone the cylinders and put it back together.

I do know my intercooler was the small core for the t28 which was not upgraded when I put in the T3/T4 but I have a bigger one geting built now.

here a pic of the piston use can see the carbon between the rings unlike the other pistons.


this one is the possible pinging or heated piston

please help not sure

I wish the pics were less blurry. I cannot see any detail.

If I could see the pictures I'd have an idea.
Diamond pistons with a cracked ringland huh?

Makes me glad I have stock ones.

Well I suppose you could rehone the cylinders if you're using aftermarket pistons AND rings but I'd recommend getting a shop to hone them because you may not have the proper clearance for the pistons when you are done.
Snap some pictures of the cylinder bores while you are at it.

If a piston has a different texture on it on one side versus the other, then I'd say you have burned/scorched all of the pistons not just the one with the broken ring land. I'd be looking at a full set of pistons and rings for your rebuild and definitely look into upsizing them and the bore another few thousandths.

I do believe I told you it sounded like a cracked ring land to me last night on the phone. Guess I called that one. My best guess on your failure is due to improper build/tuning on the engine. I'd just about bet the farm that the damage was done before you got the car fully tuned/monitored and it just took a while for it to show up. Also, how did you come up with the 900 degree range as being the optimum? I don't know the exact range, but that sounds low from what I've heard. Optimum range should be found by using a combination of the dyno, A/F ratio, and the EGR temp to find the best balance between the 3. I know you said you were running a bit rich which could cause the low EGR, but what most people don't realize is that too rich can be damaging to the engine as well as too lean. If the plug fouls out due to too much fuel and then ignites an excessive amount, then you've got a similar issue to detonation.

My personal recommendation would be to get a rebuild going and go with a reputable builder that knows how to build newer style engines. The tolerances are so tight on newer engines versus old style, that a lot of times the builders stick with old tried and true building practices that just don't transfer from small block fords and chevy's into the newer style engines.

Sorry,
Rick (learned the hard and expensive way too)

Well My EGT run in celcius rather than degrees fareheit there is a redline that start at 900 celius to 1100 celius which is maxed. Ad coverting it to farenheit is 1560 It blinks which has been done before chris reburned my chip when I had 24lb injectors now 50 lbs. I not sure if I would blame my rebuild as the problem but tuning yeah more likely. When I buil the block the guy who balanced my crank bored , etc had all my parts to gauge all the pieces. Plus I plastic guaged all my bearing to the tee and filed my ring to 20 thouasands etc. I had great compression number for months and miles. When the motor went it did go at once.

If the pistons are bad just because of little detonation then I am going to buy the 3 liter motor and build that one versus the 2.5 liter. Unless my pauter rods can't be used and my ported head with 3 liter valves can be used.

yes you were right rick it was the ring land.

but I did do have a burned chip from chris SVT which is identical to mine. I basically followed his build by the part.
I can't seem to get the camera to take a close up pic of the piston 399.00 cam and it sucks in detail.
I might be exxagerating the texture on the piston because it just appears different just by texture.

Another words what considers a piston bad obviousily a broken land does but does a variance in color or surface texture does?
If the pistons is not deformed or the structure is not altered by strength properties then it must be still good right?

Just because one side is more heated than the other does it make it bad?
I can see that one who has to not actually fork out 900.00 bucks for pistons can just say yeah just change like the mechanic would say.
But if the piston can go the life of the motor and withstand 700+ hp in new conditon could I push 500 hp on used pistons with a slight blemish on it?

I do thank you for comments but I would rather have info as to why you would think all pistons are bad too.

Ok.

Pauter rods will work in a 3L as well.
If you go with a 3L then your 2.5L heads with bigger valves would be better off sold and would easily be worth $600, enough for some pistons I'd guess. The new 3L heads can be adapted and will flow just as much or more as you 2.5L heads with big valves so why not recoup some money on those Rare heads of yours.

On the other hand, Stazi has 2.5L forged pistons he was going to sell and changed his mind. He may be willing to sell. You might come to an agreement with him on them and then get them installed.

If I were you I'd just stick with 2.5L if you are keeping the heads.

Try some different settings on your camera and don't get so close to the piston with the camera. I know my digital does the same thing if I zoom in too much and get too close. Stand back about 4 feet, DON'T zoom in with the camera, and then use a high resolution like 1024x768. Take a couple of pictures and look at the results. Then later on you can zoom in using the computer software when you get them on the PC and it should look really clear.

Without good clear pictures of the damage, the pistons, the cylinders, we CAN'T give you a valid opinion on what we think you should do.

BTW, if you exceeded 900C for any length of time then I'd worry, a quick blip over 900 maybe not. Mine likes 750-850C range when I'm running it hard, never hits 900 though it can get close when everythings hot.

Burrita - if you want my 2.5L (9:1 CR) Diamonds (with rings etc) - I'll give you a killer deal. Let me know by PM

The reason I'm guessing about replacing the pistons is that when I melted my set of stock pistons, the main indication of them melting was a change in the surface texture on the top of the piston and it was only on one edge as well, but we can tell with better pictures.

Thanks,
Rick

Holt crap! Got Macro on that camera? I think that's actually a Yeti in those pics.

Yeah. He'd be a heck of a lot better off and safer just to pick up some ahhem...sweet pistons at a sweet deal and get a shop to check out his bores IF he has the same symptoms.