That looks like the same head gasket that I use on my Gen 5 engines. On the instructions Fel-Pro said for use with Gen 5 and 6. Can be used with Mark 4 with modifications. Something about opening up some other holes. I'll try to find the instructions. Can someone else read the part number from the picture?

Looks like 17048?

That's what I thought. Better check with Fel-Pro to see what needs to be done to fit Mark 4. I'm at work and I can't look for the instructions right now.

Patriyacht,

I would appreciate that very much. Tried to find them on the net but no luck. Engine builder is very experienced , but it don't hurt to check..

tech # 1 800 325 8886

also we had gas do this two years ago but we got 3 pistons and it was rich with low timing and it did it on a 3/4 pull not wide open

Mike,

I was at about 4300rpm just easing boat up to speed slowly. WOT is 56-5700rpm. Timing 36* I think that the ceramic coating on the pistons saved the others, or I would have seen more damaged pistons.

Sutphen,

Thanks for taking the time to look that up.

I found the instuctions. These gaskets also fit mark4 bowtie blocks so you do have the right gaskets. On mark4 passenger and high perf. blocks, holes have to be drilled in the block on the outside between the cylinders. Bowtie blocks already have the holes. Your gaskets are positioned correctly also. The hole at the front is blocked to force coolant to the back. Sorry it was just an idea. Hope you find the reason.

check the ring lands on the orther pistons i have seen them burn and it not show up on the top of the pistons also check the cap and rotor for cross fire or tracking in the cap and check the jets in the front of the carb make sure they are not stopped up

I would doubt that bad gas over a few months did that much damage. What kind of compression are you running? I see you posted 9.4 but these pistions look like they have at least a 16cc dome or better. From the looks of the pop ups on the pistons it looks like they are about 11-11.5/1. I see you are using steel heads as well. I would think its been detonating the whole time and it just let loose the first of the year.

Looking at the piston, notice all the black is in the quench area. Its pre ignighting before the spark. The side of the head that has the plug is the cleanest area. That look should be 180 on correct firing.

I would check the compression ratio again.