Peteff
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| posted on 7/2/05 at 09:37 AM |
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Quench?
Is that a foreign word for squish? We had a Pinto burn a piston just like that years ago and never figured out what caused it. It actually melted the
edge off the piston and holed it. It was in a Granada 2 litre and we put a new piston in and ran it for ages after without any more problems. If
it's a standard head and the squish area is wrong in one cylinder it's going to be wrong in them all. If you don't know the history
of an engine it's impossible to speculate. It could have been run without water for weeks on end or run on experimental fuel 
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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DarrenW
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| posted on 7/2/05 at 10:41 AM |
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This may or may not be linked to this problem, but worth sharing to avoid similar experience.
i saw a Porsche engine with bad (ping pong) marks in head and piston crown. So bad that a liner was also damaged. Root cause was the ball out of a
cheap low quality ratchet dropped in the spark plug hole when plugs were changed on the cheap by the owner. Damage cost well over a grand to fix.
On old engines it is quite common to get rubbish accumulating around the plugs (not so much DOHC's). Good tip - clean them out before removing
the plugs.
Moral - dont use overly cheap tools and keep them in good condition.
Darren.
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NS Dev
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| posted on 7/2/05 at 12:26 PM |
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quote:
Originally posted by Peteff
Is that a foreign word for squish? We had a Pinto burn a piston just like that years ago and never figured out what caused it. It actually melted the
edge off the piston and holed it. It was in a Granada 2 litre and we put a new piston in and ran it for ages after without any more problems. If
it's a standard head and the squish area is wrong in one cylinder it's going to be wrong in them all. If you don't know the history
of an engine it's impossible to speculate. It could have been run without water for weeks on end or run on experimental fuel
Crikey Pete, being a bit picky!! Quench area is the same as squish area, it's not foreign, just different terms that different engine builders
use, I happened to have that one come to mind first!
I wasn't saying the squish area was wrong, I hardly think I am going to question a major manufacturer on something that simple!!!!!
What I was saying is if anywhere in the chamber is going to detonate, it is the quench (or squish!!!!) area, hence your burnt granada piston.
What caused the detonation is anybody's guess I agree, and there is little point in speculating now, but I would guess overheating, usually one
end of the engine heats up faster due to the natural water flow through the cooling passages.
Scenario was probably........mondeo runs low on coolant (maybe suspect head gasket weeping a bit) gets driven without too much maintainance and
checking, overheats on a crucial journey so the driver continues until he can get some more water at a garage, but by that time it has been pinking
its bits off for a couple of miles and the piston, having less cooling than the cylinder head, bears the brunt of the damage caused by the pinking.
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Peteff
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| posted on 7/2/05 at 12:39 PM |
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Not being picky
I'd just not heard of quench before. I wrote the post in the order I thought it in and didn't mean to sound picky. The thought about that
just reminded me of one that had burnt a valve and the top of the piston looked like it had been shotblasted. There were balls of metal left in the
bore and it needed a rebore to fix it.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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NS Dev
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| posted on 7/2/05 at 12:45 PM |
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Sorry Pete, just got all cross!
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big_wasa
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| posted on 7/2/05 at 07:47 PM |
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Thanks guys, Generall opinion is that its been run hot at some point.The carbon deposites cover the damage so it would sujest it had happened at some
time in its past? So may run for a bit longer?
Have decided its not good enought to go into the finall car ,but I am going to stick it back together and put it in the sierra to develop my ignition
and bike carbs to get my £50 out of it .Who knows if it survives that I will go kill it at a track day befor I strip the sierra.
Have spoken to the guys that surply Tiger with there donors today,They had at least half a dozen engines instock today all low milage(silver tops)
1.8 lt 39000 miles guaranteed £175+vat
1.8 lt 75000 miles " " £130 +vat
2lt choice of 2 69000+79000 £225+vat
and 1.8 black tops for about £180+vat at that money it can not be bad?
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britishtrident
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| posted on 7/2/05 at 08:46 PM |
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Show the piston to the guys are your local cylinder rebore shop -- I know what they will tell you.
While there get a price for a single piston.
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big_wasa
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| posted on 7/2/05 at 09:55 PM |
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Again thanks guys you win some you loose some but you always learn some.
It was only £50 and thats 1 saturday night out for some .And I may get some of my money back for the bits on ebay head ect .
make that £45 Ive just sold the inlet manifold for a fiver
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NS Dev
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| posted on 7/2/05 at 10:17 PM |
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as I mentioned, if you don't mind the work and the cost of a top end gasket set (no idea how much these are on Zetecs, but I guess not too bad
as they must sell a few!) then I would bung it back together and run it for now.
Ok it's far from good but will get you mobile unless the piston starts picking up on the bore, and as I said, there should be marks on the
piston if it has.
Just check the head with a straight edge first, in case it is warped, it would be annoying to waste money on gaskets if this was warped too!
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