Melted Aluminum

We melted head material in #2 cyl., warped the valves bad, pushed the hd gasket out and pushed the o-ring wire out of the block deck.
I just figured that it got lean, maybe a plugged nozzle, but the spark plug ground strap was not melted off nor did it show signs of heat (besides the melted aluminum residue). The piston thin spots were not melted, only damage to it was right where the head melted.
The inside head bolt was loose.
I have records on every run of the plug readings and looking back I was running about half a burn on that cyl.
So I put slightly different heads on and changed the piston. The heads flow nearly identical but the chambers are .25 point less compression.
The nozzle wasn't plugged, my records on plugs didn't show lean and I now had less compression so I ran it twice without changing the nozzle (only adjusting MP for weather) and at the end of the second run (a winning run) it did it again.
This time the thin spots on the piston show the heat, along with the same spot in the head. No damage to the head gasket this time, nor is the bolt loose and again the plug shows no signs of heat (like a melted ground strap). The valves were warped and the seats needed to be ground.

Could a SM IV suddenly have different timing in one cylinder?
Any ideas on what's going on?

 

Some cylinders run hotter than others, and depending where the lean spot is, the heat won't show on the plug. I have found that our plugs can look like they came out of the box after the run, but the head is torched as you describe, and there was enough heat to distort the valve and seat.

I think it is happening early in the run, perhaps when a high speed is open, and the cylinder gets lean enough to detonate and lift the head off the block. We cured it by adding more nozzle to that cylinder, and by making sure the heads were torqued to max for the size of studs that are in the block (140 ft-lbs for 9/16 studs top row, and 110 ft-lbs on the bottom row). Inside studs must be torqued to 45 ft-lbs, and new gaskets have to be re-torqued after sitting over night.

Also make sure you don't have any sharp exposed edges inside the cylinder, especially steel spark plug inserts. Is the bearing showing any signs of detonation?

 

He said it pushed the o-ring out of the block. Could it be that the block is o-ringed and no receiver groove in the head? Once it pushed it out, it will wreck everything because it will also suck air in there and make it uncontrollably lean. A perferred method is to o-ring the head with a receiver groove in the block. That was a problem we had a long time ago.
Just my 2 cents,
Kevin

 

Yep, the first time it pushed the wire out but not the 2nd time.
The wire is in the block and in this motor there is no recieving groove. The plan is to change to wire in the head with receivers in the block. but,,,

the confusing thing is,
Why doesn't the spark plug show it?

 

If the heat range is off I believe that could happen. The piston should show some melt though. If the wire is in tact and the piston and spark plug look good but the head melted then I am at a loss. Unless it is a repaired head then maybe the repair becomes a question.

 

what do you mean by frost? a slight white coating? is that showing lean also and not burning the plug?

 

What the .......

These links are like 50% nitro I want to try it to see what happens, I am just scared of the consequences.

Richard Gavle