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Author Topic: Oh cock! Melted a plug!  (Read 18680 times)

Offline Robin

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Re: Oh cock! Melted a plug!
« Reply #45 on: January 06, 2009, 08:21:34 am »
this engine has never melted a piston andy.
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Offline Andy

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Re: Oh cock! Melted a plug!
« Reply #46 on: January 06, 2009, 12:25:23 pm »
Ah, just assumed that it'd been 1341'd because of a meltage...
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Offline Robin

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Re: Oh cock! Melted a plug!
« Reply #47 on: January 06, 2009, 06:17:09 pm »
nah it was 1341'd because the guy who bought it off me wanted to rebuild it and thought he might as well go 1341cc....................got all the receipts for it and totals over 1k!
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Offline Robin

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Re: Oh cock! Melted a plug!
« Reply #48 on: January 06, 2009, 09:32:11 pm »
Right final conlusion on why this happened.

After spending some proper time looking at the head and taking the valves out it occured to me that cylinder one spark plug has been helicoiled in a previous life and it looks like the wankers who did it had drilled right through the sodding face of the head!

They basically got a massive fuck off drill and smashed it all the way through cutting into the seat for the inlet valve and also weakening the exhaust valve seat!

I think pics will do the talking! (Ignore the marks on the Cyl 1 face - head got caught on the boot catch when i chucked it in there)







Pikey mo fo's!
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Offline Andy

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Re: Oh cock! Melted a plug!
« Reply #49 on: January 07, 2009, 06:02:56 pm »
Kind of explains a lot! Probably is also the reason that no.1 plug didn't look normal prior to all this happening - guess it wasn't making particularly good compression in that cylinder?

Anyway, it's great that you've found the cause - at least it can go back together now without worrying that it could happen again.
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Offline Robin

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Re: Oh cock! Melted a plug!
« Reply #50 on: January 08, 2009, 12:32:56 pm »
Bit of an update, had the valve looked at under a microscope and it looks like it has melted due to exhaust gaes passing past the seat and the valve, the valve seat surface is pretty minging on whats left of it.

Hopefully this will bw sorted out on my next head as i am currently in the middle of lapping them in.
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Offline giorgio

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Re: Oh cock! Melted a plug!
« Reply #51 on: January 08, 2009, 09:12:12 pm »
Gutted but like Andy says at least its a relatively easy/simple fix.

Whilst your here robin - you got any more pics of your rad set up. You have inspired me
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Offline Dan

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Re: Oh cock! Melted a plug!
« Reply #52 on: January 08, 2009, 09:27:17 pm »
You can see there that the plug would have sat further away than it should be, due the thread insert. It also looks at the wrong angle too. This will have an adverse affect as the flame would have taken longer to travel and have had a more shrouded path, possibly leading to localised heat affecting the exhaust valve there.
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