Piston broke!

[andrew123e]

One for JAN….
My father broke down en-route to Kemble with head gasket failure (997 Anglia around 75K miles; coolant loss to atmosphere – no water in oil or vice-versa). Took head off this afternoon and there is evidence of water leak from front left corner of head and blow between No 2 & No 3 cylinders also). He got car home courtesy of AA.
The bigger issue is that there’s a 3/8″ dia hole through the centre of the crown of No 3 piston. The head has never been off before and the other pistons and bores appear excellent (virtually no ridge at top of bores even on thrust side of block). The car has been run on unleaded without additive for several thousand miles – I previously thought we may as well do this as any wear/erosion to valve seats will be machined out when seats are eventually machined out/replaced with hardened ones. Do you think this has resulted in a hole burnt through one piston or do you think it’s more likely to have been initiated by a foreign object at some time in the past? Difficult to tell from nature of damage.
When I recently adjusted valve clearances I noticed the exhausts had closed up a few thou so seats need replacing anyhow.
Will probably replace the piston if rest is as good as it at first appears on further strip-down.
Andrew

[PeterDenice]

Andrew
Sorry to hear about your problems, not heard of unleaded affecting the pistons before, is it possible it could be due to the overheating.
If the piston is standard size & you need a replacement drop me a line, I have some second hand ones in the shed you are welcome to.
Pete

[Ken B]

I think a possibility the timing was out. You really need to be running 8 degrees BTDC static I found to be the optimum all the years i ran Anglia engines on u/l.
Having said that I would say you’d have to be giving it some stick to do that, and I cant see you’re father doing that. But did he not used to tow a trailer with his Anglia quite often? quite possibly a combination of factors there I think.

[JAN]

Sorry, I saw this a couple of days ago but forgot to come back to it.

The cause of the hole is open to speculation, but I doubt that using unleaded without an additive is the culprit. I’ve just removed the Prefect’s engine to fit the one I’ve rebuilt, both 1198. There wasn’t anything wrong with the first engine as such: it ran well and quietly. But it had over 70,000 miles behind it, all on unleaded, with no apparent damage to pistons or valves. I simply decided to change it at a time of my choosing, and while it was still in good order.

Did your engine start to make noises before it expired? Did it run very hot first? The lack of water in the oil is suggests that the head gasket wasn’t the cause, but if the engine did become very hot…?

Had it been a foreign object, you definitely would have heard it, and the hole would have appeared immediately, followed by a dramatic loss of power and oil fumes everywhere. Over-advanced ignition is another possibility, as is too hot a spark plug, or a VERY heavy build up of carbon. But whatever, the piston damage is what caused to engine to expire, not a head gasket.

[andrew123e]

Thanks for the replies.
Pete – I’ve PM’d you about a piston.
Ken & Jim – I wasn’t in the car when it expired, and my father just says it overheated – not much more detail I’m afraid. There was very little carbon in the head or on piston crowns for the mileage, along with little bore wear (barely perceptible lip at top of bore on thrust side). Be interesting to see how the crank and shells have worn on disassembly. Haven’t driven the car myself recently so don’t know whether it was pinking – I had replaced dizzy before the trip as old one had very bad shaft wear. Should have driven it on road afterwards but it was a hectic week trying to get our car & caravan ready as well.I had set timing to 6 deg BTDC – car only went about 80 miles afterwards. Plugs were a nice/normal colour. Ken – you’re right – car has towed a trailer to several shows, prob less than 1000 miles total.
The plan is to strip/assess and repair (crank grind prob necessary).
Andrew

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