Is there a spark plug doctor in the house?

[WSLN 6]

A little background....
Doing some tuning the other night, 17psi, 21 deg timing, 10.8 afr, 94 octane and meth. No knock. 3 Egt's less than 1370 degrees in the passenger header ( driver side need relocation before use unfortunately.)
Heard a small pop and a weeeeee noise, followed by a loud exhaust ticking noise.
Felt around the header, no leak felt. Sounds higher up.... Looked at rocker adjustment, nothing has moved with all pushrods right where they were before.
Compression test 150 for all clinders except for #5 which is 125. Here is a pic of the plug.
Diagnose away!

 

[TurboBob]

what do the other plugs look like?

Bob

 

[WSLN 6]

A little on the rich side, but normal compared to that one.

 

[charlief1]

Looks like it may have an injector problem. Maybe clogging up or bad electrical connection?

 

[GARY HARVEY]

Is the car run on a regular basis?
How many miles on the engine?
Was it at temp when it mis-fired?
In what condition are the ignition coils & wires?
The voltage correct?
Plug looks wet BTW. Try a short cruise (20 miles)
then pull the (same) plug and have a look.

 

[WSLN 6]

New pistons/rings this round. About 50 miles on the engine.
New Msd coil/distributor/wires etc
Dual Walbro pumps running full time.
Temp was at 175 when the problem happened.
220 amp alternator, voltage was at 14.1
I highly doubt I will be driving the car without doing a leakdown test first.

 

[GARY HARVEY]

I'm with you, leak test and if you can
find a bore scope to peek the cylinder.
Good Luck

 

[WSLN 6]

Leak test was great, and a better compression gauge verified 160+ on all cylinders. Found my exhaust gasket totally cooked on cyl 5 from the bolts being loose, was rapping against the firewall.
Runs great again, new plug. Will keep an eye on that.....
Ran 14.5 at 104mph last night on 6psi lol.