Oil out of cam breather

[gitters27]

Well I fired up my new built C16SE tonight I’m running twin 40s.
Started up after 5 turns beautifully,went for a drive 7 miles in starts missing/smoking out of exhaust and oil out of the cam cover breather,removed all 4 plugs to find number 4 oily,I’m thinking blow by what are your thoughts?? Can’t find my compression tester,what compression should I be looking for roughly? Can’t see it been a hole in piston from running lean.
It was smooth,no smoke and no nasty noises just suddenly smoke then missing

[total_vauxhall]

maybe the rings died

[House]

My 20XE did this, number 1 oil control ring was screwed.

[millworm]

First step would be compression test check all and that will give you a good idea of what 4 should be if it comes back low. If its not a ring then I'd maybe be looking for a stem seal that isn't seated properly after the rebuild

[Iain]

First step would be compression test check all and that will give you a good idea of what 4 should be if it comes back low. If its not a ring then I'd maybe be looking for a stem seal that isn't seated properly after the rebuild

Stem seal wouldn't start pressurising the crank and forcing oil out the breather though.

Could be a piston ring, or maybe headgasket? Compression and leakdown test will help but sounds like the heads coming off as a minimum to investigate.

[gitters27]

I’m on holiday so once back I will be testing compression,I’m wondering if one of or all the other rings are losing compression because if oil is forced past cylinder 4 piston compression must be getting into crank from one of other piston or pistons to be pressuring the bottom end,really can’t see head gasket failing

[gitters27]

Rite landed back in the uk so pressed on with this,used my cheap compression tester and numbers 1 2 and 3 were only at 75psi which is half what I expected.number 4 had 0 psi.
iv removed the head and found on the inlet side of piston melted.
what are your thoughts??
im going to pull all the pistons to check rings and timing of rings.
i think iv had my ignition to retarded,which caused the hole in piston

[gitters27]

I did do the compression test cold for obvious reasons,compression test carried out without throttle open

[gitters27]

Just got off the phone with David bogg he says it sounds like a faulty piston

[Will F]

Were the pistons new? If its melted, its more likely to be down to ignition/fuelling and it running extremely lean on that cylinder.

[gitters27]

No original pistons,I think the same but he said because it was only 7 miles in he would be more towards faulty piston.looking at the piston it has hairline cracks which could of been the start of it failing