Chamber temps go up with lean A/F. since you only melted 1 piston, lean in that bore. A vacuum leak is unmetered air, and lean.



That piston melted in about 3 seconds of WOT, from a vacuum leak.
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Your vacuum leak being unmetered air causing a lean condition statement is true... when there is vacuum. Unfortunately, there isn't any present when you're in boost. This is also much more prevalent in cars equipped with MAF sensors and it actually causes richness in boost. F series utilize a MAP sensor which meters pressure, not air flow. The pressure the map sensor sees is the pressure that the engine is ingesting whether there is a leak or not. The only way i can see your theory working out is if your leak was between the intake manifold and the head in that cylinder or at the lower injector port and positive pressure was causing the fuel to be pushed out instead of into the cylinder.

 

Which is why I asked what intake manifold gasket he's using. Under boost there will still be a pressure loss. It's all speculation at the moment, we don't know what cylinder that piston came from, or where the methanol/water injectors are.

 

Cyl 1. He said it in first post. Third times a charm. Shits gonna be on point with race gas.

What did u make on pump?

U changing anything :diff or trans or gear ratio?

 

Not sure what I'm changing yet. Just fueling options I'd say.

Stock trans and diff for now. Just want it running so I can cruise this summer. Mess with that crap over the winter.

Watching my money, also house shopping.


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Cyl1.


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I'd be checking cylinder #1 meth injector and line for being clogged. That bore went lean.