melted piston..but why?

[Jono]

My 5 melted a piston this evening. Which is bl00dy fantastic. I will try and get some piccies up later.

I have whipped the head off and No.1 ( Flywheel end) has melted round the edges.

So a couple of questions, will the head be Ok to re-use? I think I already know the answer to that one.....

Secondly:

I was running about 18psi , AFRs were in the low 12s. Clearly its been detonating but I dont know why? Before I stripped it I checked the AEI feed line and it was leak free. Im running a full T25 ( which now has chipped turbine blades - so expect it in your in-tray Adam L...) and a twin capacity intercooler so I wouldnt of expect the charge tempts to be excessive.

Thanks for your help in advance Gents.

[Scoff]

you aught to measure the height of the cylinder head, it should be 73mm or more. Much less and there's your answer. After that you should check the operation of the AEI. the capsule may be leaky, or stuck and innefective.

[Jono]

Scoff,

Just checked the head thickness, its 73mm.

ta.

[J$£5GTT]

thats what happend to me,you may be ok with just replacing the piston
and liner for a used item and obviously sorting out what caused it in the first place,

[THE MASTER]

jono have you got any pickys

[rs250nut]

you aught to measure the height of the cylinder head, it should be 73mm or more. Much less and there's your answer. After that you should check the operation of the AEI. the capsule may be leaky, or stuck and innefective.

After the other week when I removed my head I saw traces of det and could not get my head around it, measured it after a good think and it measured 71.3mm No wonder it felt livley at low revs.

[Jono]

a few pics.

[Jono]

The pics were taken last night just after I removed the head.

Today I have removed the sump and popped all 4 pistons and liners out.

Obviously no.1 piston is mullered, though the liner looks in suprisingly good condition and its not split.

The other three pistons are all showing signs of detination too. They must have got pretty hot as the part of the piston that rubs up against the liner say the 6 clock position looks like its been freshly emery papered, if that makes sense! I will get a pic up tomorrow.

[THE MASTER]

i would be interested to see all 4 pistons

[Jono]

A few more pics

[Jono]

I just noticed that one of the other liners is cracked too. This probably explains the slight water loss I was getting. The level would drop from max to min over a period of 2-3 weeks. I just presumed I had a tiny leak somewhere.

Also I have a spare 209, but the module nipple is snapped off. Is there any way of replacing the module?

[Jono]

anyone!!??

[R5GTTRaider]

dunno if this could be right by saying it could have been running lean? just a thought?