Carbon buildup

[s851]

Hi all,

Just got the head of my 2.25P (IIA, 1972 ex Mil) and this is what the tops of the pistons look like. The engine has done 36,000 miles; does anyone have any experience with this? Is this an acceptable level of buildup?

Wasn't planning to remove the pistons...

Thanks
Philipp

[Blknight.aus]

thats not too bad aand IVe seen worse.

if the compression was good its most likely from

1. not enough advance for the running conditions
2. running to rich
3. leaking inlet valve stem seals.

[s851]

Thanks Dave, yeah compression was bang on for all four and the machine shop guys said the vale stems were shot, so that might be the cause..

I think i'll just leave them as they are then.

thanks again
P

[JDNSW]

I would describe that as pretty normal - probably it is burning oil, which may be from, as suggested, valve stem seals, or past the rings (not necessarily correlated with compression) or even overfilling of the air cleaner. This engine always uses a lot more oil than is acceptable in modern engines, and some of this oil consumption inevitably ends up as carbon in the combustion chamber.

John