Piston and head damage

[Iain]

C20XE, #4 cylinder. Damage to head and piston. Wtf has happened?

http://uploads.tapatalk-cdn.com/20160507/3dc09057e78d27292753d69b09405670.jpg

http://uploads.tapatalk-cdn.com/20160507/83dffd7e88cc1033c7f3b944597fcc06.jpg

[Plug]

Somethings got in there and caused some damage :(

[Iain]

I would expect it to be all over if it were debris?

[Jonesfach]

What's the bore of the cylinder like?

is it an engine that you knew was ok previous? Could be old damage?

could it have been running very lean and got very hot in this cylinder?

[Will F]

It could be detonation but that would be really severe to cause that much damage on an n/a engine...

in fact it's not detonation (just had a better look) something has def been in there but it is strange that it's been isolated to those areas. How's the plug?

[Iain]

Bore is very slightly scored from piston deformation

Engine was all mint when put together. Professionally inspected head and pistons were all good.

It could have been lean on #4… it's something I need to investigate.

Plugs fine little black but not damaged.

[Jonesfach]

Carbs? Injection?

cant be due to timing as all 4 would be goosed so it must be dodgy plug, running lean and hotter than normal however if it was too hot wouldn't the damage be around the spark plug not where it is? Does look like its melted somewhat.
If there was shit in the cylinder it would have blown out fairly quickly and only made slight marks? Probably more pronounced too.

[Iain]

Ok done some further digging.

The plug looks slightly bent so led me to think of debris

Peering down the inlet and if looks like the valve guide has slipped out of place and a piece has broken off.

Strip down of head tomorrow to prove this. Why the guide has slipped I do not know.

[House]

I'm so sorry mate, that head was inspected and the 8 exhaust valve guides swapped out, the inlets were all solid and within tolerances. I was so worried about supplying something that wasn't up to standard.

I'll get this spare engine on a pallet and sent up to you for Wednesday.

[Iain]

Shut up you drunk, nobody blamed you lol

The valve guide has indeed broken up and been munched, good times.

http://iainel.co.uk/images/forums/NovaWIP2b/284.JPG

[Stuart]

Better flow with the guide now flush lol

[Iain]

I think the extra flow is offset by the incredibly low compression haha

[Stuart]

Chuck a turbo on that one cylinder

[Iain]

I may try an in-place hone and new rings on a spare piston I've got. Then I just need a new head.

There's some very light scoring probably from piston deformation or the debris.

http://uploads.tapatalk-cdn.com/20160508/1db67a7b80e45b0d4c74492ef94032b4.jpg

[Stuart]

I reckon you'll just about get away with that. Use the ball home thing (kinky)

[Iain]

Link? Never done it before but got a spare block I can practice on. Small lip at top so feel it's worth a try.

[boffer8]

Whats the engine used for?

To be honest i think this is all re-usable.

The head just needs cleaning up, removing any sharpness from the indentations and a new guide if not a set putting in the head (just to be on the safe side). They should be reemed to fit snuggly and any decent engine shop should be able to do this on oversized guides to ensure this doesn't happen again.

Your right about the block and in terms of fitting new rings to only a partially honed bore you may experience issues. Drop the sump, undo the rod bolts, push the piston up and out, use a decent fine file to dress the piston and then do a bobble hone, use WD40 on a decent lint free rag and make sure the bore is properly cleaned out before re-inserting a nicely cleaned and fettled piston (with current rings) fitted.

Fire it all back together and she'll be mint. Have done this a couple of times on 8v engines and not had any concerns or issues following doing this. Certainly a good way to do it saving all the other hassle.

[Iain]

I've kept the head to one side to look at getting repaired. It's just for trackdays but tends to sit at high revs as you'd expect.

I've picked up a recon head so going to chuck that on for now, saves me the hassle and delays up front.

The piston is totally scrap, and it has deformed to clamp on the top compression ring. I have cleaned a spare piston and ordered new rings ready to go on. I have a 3 legged deglazer which I'm going to run up and down a few times.

You think I should be reusing the old rings rather than fitting new? I did struggle to get the rings out of the current piston it's that tightly clamped, and the ring gap is out of tolerance whereas a new ring brings it back in, just.

[Iain]

Old rings isn't a goer. It's trapped in there good and proper.

http://uploads.tapatalk-cdn.com/20160511/ec131ec714162fd45c85b96df0fc4afa.jpg

[boffer8]

If your doing a proper deglaze then use new rings, if not then use the old but looking at it they are, and the piston for that matter, buggered!

[Iain]

Ill keep the 3 legged in there for a bit longer and give it some good cross hatching. That's all I can do at this stage

[Andy]

What grade glazebuster is it? Dont go too mad as its quite easy to go oversize as i found out practising on some 205gti barrels i had spare when i first started building my own engines.

[Iain]

I've been practising on an old block too. It's borrowed off someone but they said it's the finer one. I borrowed a proper bore gauge too but not got a 86mm micrometer so gonna pikey it and measure via ring gaps. I won't go mental with it tbh

[Iain]

http://uploads.tapatalk-cdn.com/20160511/ce5a17f9c4d257feea1d81723fa6f0d7.jpg

[House]

Chuck a turbo on that one cylinder

This made me cry with laughter.....it's plausible!!!!