oily sludge on pistons.

[Jankenshank]

so im puzzled.... i have a fully built engine, head and block, and has only been rebuilt 800 miles ago.

i pulled my head the other day, to find a black oil/tarry substance on three of the four pistons, the engine has less than 1k on it since the complete overhaul,

the one piston that didnt have the oily substance on it looked brand spanking new!

any ideas what might of caused the oily substance?

pulled the head due to a Overheating problem only to be puzzled by this..

the HG was leaking on cylinder two toward the front of the block...

could it be valve stem seals?

from left to right
cylinders
4-3-2-1

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[BoredDSM]

You should have ran a compression test and a leak down test before you took it apart. It can be piston rings causing blow by, valve seals, head gasket, or maybe just some oil was left in the head and fell in the cylinder when you pulled the head off. Doesn't look like a head gasket though from the pictures. How did you break in the engine? Did you do the break-in intervals of changing oil?

 

[Jankenshank]

i didnt change the oil, i just ran it for 400 miles shifting at 4500RPM,

then pushed it last weekend and it detonated then started to overheat,
flushed the cooling system and radiator, replaced thermostat, new thermo sensor, but still overheated at idle, pressureized the system and it held like a charm.

 

[crimsondragon]

What does the oily looking pistons smell like? Was the head rebuilt or just the block? Or both? Who did the rebuild? Check the block and head for warpage of any kind.

 

[Jankenshank]

it was a complete rebuild, bored block, stage 3 head, EVERYTHING new.

a performance shop down in Kingsport TN assembled and flowbenched the head.

due to the Overheat the head is warped but only just out of specs with a .006 in the center.
havnt checked the block yet, but will do when i get back home, aswell as sniffing the sludge.

 

[MichaelSuch]

Just curious what kind of oil did you use?

 

[DougR]

Exhaust valve stem seals are shot, especially #4.
Pull those and beshure to lube them up Really well this time before dropping in your valves.

GL