Birty Dastards Jeep Club
Tech Forum => Workshop => Topic started by: Green Jeep on November 22, 2012, 01:04:51 PM
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Hi,
Has anyone any ideas why this would happen? No 2 piston has a crack... 127,000 miles. I have sourced a spare engine that I can get bits off.
Thanks Maf
(https://birtydastards.com/frm/proxy.php?request=http%3A%2F%2Fi439.photobucket.com%2Falbums%2Fqq119%2Fpropref%2FCracked.jpg&hash=606176fe7d06bbe695049d80781e5600bc061dae)
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any bore or valve damage? you need to get it out really & inspect everything! Scoobys do it a lot due to piston slap, but you need to strip it for a better idea! What were the symptoms before it happened?
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any bore or valve damage? you need to get it out really & inspect everything! Scoobys do it a lot due to piston slap, but you need to strip it for a better idea! What were the symptoms before it happened?
No bore or valve damage, engine sounded like a big end had gone at 2,000, but as you revved through the noised stopped and performance was good. Previous owner said it was a stuck lifter and that in 2 years in hadn't changed.
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The pistons are graded by diameter, you'll find the sizes painted on the distributor side of the block. I just threw away a load of brand new Mopar ones that no-one wanted to buy!
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Thats a first on me - never would have believed it.
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Had this happen on a Lotus engined Cortina I once owned, that also sounded like bottom end knock.
The crack went in an arc down to the piston pin. The piston pin bore was oval, not really noticeable but measurable, so the obvious cause of the knock.
No obvious cause and no overheating. Guesses to cause - lube failure, mistake a on previous assembly or since the fuelling and spark were a bit stoneage it could have been pre ig/detonation. Replacing the piston and new small end bush sorted it, couldn't afford to do a proper rebuild at the time!
I'd wager the same thing here, probably started as a tap (easy mistake for the lifter going) then getting worse.
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Thanks guys...
It could be a fueling/timing issue as new plugs appear to have been running hot in just one weekend. Not sure what can be done about this... previous owner didn't carry out servicing, air filter was thrown away as it was black... so maybe something has entered the bore and left?
Cheers Maf
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I should have made it clearer, in my case you could see that the fracture started at the pin as it was more prominent there and only a hairline at the crown.
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Okay,
Think we have found the cause... poor servicing... we have removed all of the pistons now and most of the oil ways to the piston are blocked or only just letting oil through.
This would explain the possible reason the spark plugs engine appear to have been running hot.
New rings, big ends, etc all arrive on Monday so fingers crossed we can put the engine back together early next week.
Cracked piston was ready to fall apart, didn't take much force to break the skirt off...
(https://birtydastards.com/frm/proxy.php?request=http%3A%2F%2Fi439.photobucket.com%2Falbums%2Fqq119%2Fpropref%2Fphoto5-1.jpg&hash=fafd34ea0b62e2065dc8368542810c3953256411)