Any idea whay this may have heppened?

[Doug_Guilds]

Ford 2330. KB Hyper pistons. Engine was assembled a little over 2 years ago but only has 15 nights on it. Head was shaved 100k at the start. I had another 40k taken off of it about 2 weeks ago and swapped out a Racer Walsh .479 lift for a Schneider .480 lift with more duration. I did change the gear so I was cranking 7000 instead of the 6 I had been cranking earlier this season. This was the outcome....

cylinder #3



cylinder #4



I am not sure what could have caused this since I haven't noticed any kind of detonation problem reading the plugs. It looks to have been running a little lean but this was after 8 laps. Oh and no bent valves and no indication that they touched the piston on the valve itself.

[mustang99]

any idea what may have happened

Ford 2330. KB Hyper pistons. Engine was assembled a little over 2 years ago but only has 15 nights on it. Head was shaved 100k at the start. I had another 40k taken off of it about 2 weeks ago and swapped out a Racer Walsh .479 lift for a Schneider .480 lift with more duration. I did change the gear so I was cranking 7000 instead of the 6 I had been cranking earlier this season. This was the outcome....

cylinder #3



cylinder #4




I am not sure what could have caused this since I haven't noticed any kind of detonation problem reading the plugs. It looks to have been running a little lean but this was after 8 laps. Oh and no bent valves and no indication that they touched the piston on the valve itself.

after u milled the head more,,did u change the jets?and u might have to run racing fuel,,not enough octane in pump gas..since u have raised the compression more when u milled the head more...

[drtlvr]

Top ring butted. Pretty normal for cast pistons. Ring gap should be double that of forged. If the edges of the piston would've had black color and peeling on them, too much timing could've done that.

[84Dave]

I agree with drtlvr. The top rings may have butted. If you can find the piece of the broken ring, look at the end of the ring piece and see if they look 'shiney'. If so, they butted. Been there.... done that! -Dave-

[let-r-eat]

Very common on the hyperexplosive pistons. Open the ring gap up. With the extra off the head you need to make sure you have some octane. 93 octane likely isn't going to run that engine.That little side of the intake valve relief is the weak spot on all pistons. Detonation will break them off exactly the same way.Open ring gap, good gas, 38* or so timing, Good plug color, mill the head some more, throw the headgasket over in the trash and gas on her.

[Doug_Guilds]

Thanks for the info guys, I will have everything apart later in the week and see whats up. Cylinder #3 still has the ring on top so I may be able to tell from it. I think the end gap was somewhere around .028 maybe. It has been 2 years and I am not sure if i wrote it down. If I find the formula they recommended I can say for sure because I used the one from KB's web site. The fuel is a 93-110 mix. That should be enough octane but I will check everything over good to see what I can find.

EDIT- It was not .028 I think it was .019 after looking at the site. They recommended .015-.040 and I believe the calculations I had made were .019 for a .030 over 2300.

[84Dave]

Doug......... I'd definitely suspect the top rings butted. .019" end gap, I doubt, is nearly wide enough on that top ring. -Dave-

[Doug_Guilds]

I think you are right Dave.

I talked to the guy that does my machine work and he said that he thought .019 was a bit to close also. I am taking the block and both pistons to him so he can magnaflux everything and make sure there are no cracks in the cylinder walls, and look over the pistons to see what he can find. There was no water in the oil so maybe I got lucky there.