CafeRacerPTY

Went out for a small run yesterday and once i got back i noticed that 2 plugs were burnt. pics below of one burnt and one not burnt. Also, one of the cylinders has no compression now. I think im taking the head of that side to check if the valves are closing correctly.

Any suggestions as to what may have caused this?

JeremyAnderson

The porcelain has a green tint. Green=lean. Tuliped an exhuast valve or a lifted ring land is my guess. Now, why did it go lean in that hole????

ezstriper

it's not good....what is the engine setup ??

Ted G

iTrader: (1)

Looks like detonation damage, if you really have 0 compression you likely holed a piston.

Throttle Fever

iTrader: (9)

I am with Ted, Lets hope we are wrong.

FIXX

iTrader: (2)

All the above! or blown head gasket between cylinders,if so hopefully it didn't hurt the deck of the block..502???

1BIGJIM

iTrader: (1)

What cylinders? What year?

Whey you burn a hole in piston you will see metal all over the plug and the plug will look worse than that.
I would also go with blown head gasket.

I had a problem last year with zero compression in one cylinder, it was an exhaust seat. Valve was not closing all the way.

lightning jet

my guess is a head gasket,was there any water in the hole?

ezstriper

don't think a head gasket would burn the end of a plug off like that...

CafeRacerPTY

no water in the hole. the pistons are new 4.530, block is a 502 bored to .06

i think that i have a combination of problems, thin head gasket (.03) hot spark plugs and low octane gas.

the oil was clean as well