BillK

Also wanted to add that those do not look like the correct head gaskets. They are awful close to the bore and are probably hitting the chamfer at the top of the bore. Might be whay they are getting pushed out in a couple of spots. Could also be from detonation, but the gaskets do not look correct.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

TEXASRPM

Have you ever measured the AFR ratios?

rich allen

Appreciate the comments

Some answers to questions:

-Gaskets are Felpro 17040
-Valve seats are intact
-No fly cuts on pistons. These have not been touched. In that pic of damaged piston it may have looked like it but no.
-No I have never measured AFR

I have attached another pic of different cylinder. This one is cylinder #8. It appears detonation is at work here as well? The previous one I posted was #4

Oh, and since I'm already attaching scary pics, thought you might enjoy another one of damaged piston.

jeffswav

Looks like your valve floated and hit the piston. Did you over rev?
Somehow your pics posted before my post, looks like a meltdown. Must have went lean......

DMOORE

I would double check the entire fuel system before you put the motor back in. After all of the time running the motor as is, something had to change to cause such a major problem. There's no way you were getting detonation for all of the hours running and she didn't blow earlier. Also just to be sure, I'd drain the fuel and run it in the family wagon...... just to be sure.



Darrell.

cubicinches

Everything you've got there is positively detonation related damage. Broken/lifted ring lands are a text book sign of detonation.

Here's a link to some good reading on the dynamics of normal combustion. For a much better understanding of detonation, how it is caused, and what it's effects are... Check the section which specifically explains detonation, it starts on page 6.

http://www.jcmmachine.com/PDF%20file...port%20ch3.pdf

cubicinches

The 17040 gasket is fine, but the signs of heat on the gasket, and the fire ring squirming around are just more evidence of detonation.

picklenjim

Very interesting artical you posted there cubicinches!

stevesxm

well.. this picture is definitive. you had detonation. and i wouldn't rule out the HG as bill mentions... don't treat lightly the fact that he has seen about a billion HG and when his first impression is that observation that is as good as anyone elses microscopic analysis. but beyond that... i think you have all the answers you need now to proceed to fix your motor as long as the repair is properly done. keep the CR at something you can buy repeatable fuel for, put a camshaft in that is well understood for the combination ... there is a well respected guy on here known as RMBUILDER who is apparently the cam god ... and make certain that all the parts like the HG and small bits are correct for the sizes of the bores and the pistons and all else.

no magic to any of that. as for what caused the detonation that killed your motor, that's going to come down to fundementally understanding the final operational set up... the fuel system , cooling system and timing. if it was me, i would make a trip to the dyno and dyno the thing with a dry set of headers with EGT's in them and make sure i understood what was really happening. that would be the best 500 bucks you ever spent. and i offer the same advice that i offer to everyone. get a handle on what your own skills and knowledge are and don't treat this as a trial and error deal. don't put anything back in that you are not absolutely certain of as a matter of fact. if you aren't certain, trot it off and show it to someone that knows more than you do.

you don't have to actually make the mistake in order to learn from it.

Young Performance

I'm on board with everyone else on the detonation. I also think the engine was lean. It think the ring land lifting could have been either detonation or it being lean, or a combo of both. Definitely have a look at the fuel system. Make sure you have a fuel pressure gauge the next time you run it to be sure it is holding pressure at WOT. Just because the plugs are black, that doesn't mean it isn't lean at some point. All it takes is a few minutes of rich idleing to blacken the plugs and you would never know it was lean at some point.
If your quench is correct at .050, then that means the piston is about .010 in the hole. Using that, the 26 cc dome, and 11 cc gasket, I come up with a touch over 9.8:1. That's really pushing it with today's crappy fuel and cast iron heads.
Lose the cast pistons. Get some O2 bungs put in the exhaust. Might also want to invest in an add on knock meter to dial in the timing. With that setup, you will need to run as much timing as possible to keep the egt's in check. However, a little to much and you end up right back where you are. As mentioned, a dyno is invaluable. You can monitor the egts and afr. Feed it timing until it stops responding with power and lower egt's. Every engine is different. Don't pay any attention to what the actual timing number is.....it doesn't matter. If the engine wants more timing, then give it to it. And vice versa. If it doesn't make any more power with say 36 deg. then it did with 34 deg, then leave it at 34 deg. If it keeps responding up to 38 deg, then give it to it. Don't worry about the number. It is what it is.
One last thing....pay close attention to the combustion chambers. Remove any and all sharp edges or points that can collect heat. Not only that, a good chamber will help with lowering the timing. Good luck.
Eddie