Leak Down Test Problem on #2 Cylinder

Anybody got some JB weld or a caulk gun I can borrow? Seems like I need to make a minor repair to #2 piston.

Ring Gap looks to be a little too big. Thats why your leakdown was excessive

Yikes! And here I figured the cast crank would be the first to go!

How much boost were you throwing at it?

Only to be made worse by the too large gas porting.

Welcome to the I broke parts racing club
Time to get to work to make it stronger so it will take more abuse and make more power
Sorry for your loss

Not sure where that piston came from originally, doesn’t look at all like this Chinese piston.

😂. Ah So.

There are better ways to reduce the compression ratio!

Wholly meltdown Batman!! Sorry to see that.

I have nightmares that end looking like that.

Did it launch a breather off the valve cover when this happened ?

That one looks more like the head came off a Chinese valve and beat the crap out of the piston and cylinder head?

Broken valves don't normally melt aluminum, especially like this one did

ouch....lean condition under boost?

That piston has Holloween all over it , lol Gary

Funny thing was it was barely smoking out the exhaust after a 139.7 mph pass. No oil out of the breather.
Doug

It actually shocks me how little it was smoking for how big that hole was!!!!

What you're looking at is a custom made Diamond Piston specific for my turbo application. 2818 material, Thick crown, ring is down a bunch, etc... Certainly no fault of the piston.

It had hurt the converter at Monster Mopar earlier this year, and wouldn't 60ft at all. So I was leaning on the tune pretty hard to get it to run 10.0 for the shootout (about 20-21psi of boost). Went 9.98@139.7mph on the last pass.

It's a little bit strange because the A/F wasn't excessively lean on the data logger, nor do any of the other cylinders look like they had anything wrong with them. #1 and #2 cylinders always run the hottest on this car, so as I was adding boost/timing, I was watching #1 carefully. Whoops... should have been watching #2 apparently!

We will see if the block is going to clean up. Hopefully I can just slap another set of pistons in it and go... but we'll see.


It is absolutely amazing to me that the piston can take that kind of abuse, and the stock block/cast crank still survives!!!!

Sharp edge on the valve notch likely caused that.

What Kind of head gasket do you run with this Engine?

I thought it was pretty obvious I was referring to Transman's piston pic, not the OP's melted one...
This one:

I 100% agree. No doubt the radial edge of the valve pocket makes this the thinnest area. I hand "massaged" these the best I could to minimize any sharp edge, but at the end of the day every part has a weak point somewhere.


Running standard off the shelf Cometics.

Thanks for the info, good luck with the rebuild!

Michael