Burned Melted intake runner 5 - Predetonation?

[Torquenstein]

Car: 1987 325is "C104 plug"
Engine: 1998 M3 S52B32 with OBD1 conversion
ECU: M50 Red Label 413 - 1994 325i auto
Transmission: Getrag G260
Harness: 1994 325i auto

Mods:
SSSquid Stg-2 Chip for 413 Red Label
Sunbelt Stg-2 Cams
Ford Bluetop 24# Injectors
M50 Manifold
3.5" HFM
eBay Longtubes with single o2 at X-pipe

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After our team raced this past weekend, we took off the manifold to try and chase down an issue with fuel loading up in lower rpm ranges. Upon taking the manifold off, we were surprised to see that the intake runner on cylinder #5 had been severely burned and partially melted. We inspected the cylinder and piston for damage, both appear fine and valves are sealing correctly. It's like that cylinder in particular has way too much advance timing causing a predetonation scenario.

[Torquenstein]

[Sh3rpak!ng]

I've never seen that happen. Certainly not a good sign.

[TobyB]

Do a leakdown- intake valve not sealing could do that.

t

[pazi88]

Do a leakdown- intake valve not sealing could do that.

t

Yeah it's definitely leaking intake valve and the burning mixture from combustion chamber has melted that. Which could be faulty lifter which leaves the intake valve open from time to time. If there valves itself don't leak.

[Torquenstein]

Definitely not a bad valve or lifter issue. Funny thing is, it looks more like it was just installed improperly than it was burned apart between cylinders 4 and 5. Throwing a new gasket in tomorrow and I guess abuse it some more.

[TobyB]

I was going to say your head gasket can't get back into the intake,
but I guess if it's blowing into a cylinder that's got its intake valves open,
then it could. As in, #4's igniting when #5's on its intake, after the injector's opened, especially...

Wacko. Thanks for the followup!

t