It seems like as this has happened several times there is a deeper issue you need to find, I know that you enjoy wrenching on it though

Got any pics of the plugs? I had something similar happen this past weekend due to a distributor that decided to set the timing on its own. Ran fine at 6500 rpm but didnt run so well at 4800 when the cylinder pressure was starting to peak.

Smaller cams might be building quite a bit more cylinder pressure now. Too hot a plug, to much advance, or possibly not enough fuel? Those ferrea super alloys can take alot of heat over most valves, including inconel. But if theres enough heat to start a detonation/preignition event, other things go south.


Jason, what plugs are you running in it? What was the AFR? Timing setup? (not only total but locked or curved, etc)

Always a smarta$$ in every group...lol
The original piston kissing exercise was due to to many changes at once. Changing GenV to MarkIV heads, eliminating water pump, going to a crossover and steam pocketing the rear of my heads. I have actually ran this setup for years trouble free. JimV said he will finish the head tonight and I'll have it back together and running tomorrow after work.

I'll test the exhaust tomorrow, but it is Stainless Marine dry to the tips. (No headers here) Also, I'll get the AFR hooked up for some passes this weekend. Timing is locked at 35° Crane HI-6M. Jim and I'll take a closer look at the pistons, the pics look different then when I looked at them yesterday.

How's the Baja running? Facebook tells me really good!

Hard to see in the pics, but are those projected tip plugs you have in there??

I don't even see any plugs in the head.

They are what Dart recommended for tip. Plugs are NGK 7or8 range.

[ATTACH=CONFIG]525201[/ATTACH]

Just got off the phone with Jim. He said the valve didn't stick. He believes the pushrod guide broke first, rocker walked over the retainer, released the keepers and spring, valve dropped and then the piston made sweet love to the valve. The stem shows no signs of heat, metal transfer and the guide looks relatively good.

Mild, AFR's are ~12.8 WFO!

I think I might have found my answer. More investigating tomorrow.
http://www.offshoreonly.com/forums/g...de-plates.html

Oops - just re-read your original post - you already have the adjustable ones. Interesting.