Piston problem

TonyG
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Joined: Mon Sep 07, 2015 4:38 pm

Re: Piston problem

Post by TonyG » Tue Oct 06, 2020 8:18 am

John,

I’m in Colchester, Essex, near the border with Suffolk.

Sounds as though the odd piston just fits differently but, given it’s been in and working fine, not something to worry about.

Keep us updated.

Tony.
Tony Gilbert

P1 12 Tourer
P2 12 6 Light Saloon
Discovery 3
Discovery Sport

JohnG
Posts: 23
Joined: Thu Jul 02, 2020 5:44 pm

Re: Piston problem

Post by JohnG » Wed Oct 07, 2020 8:04 am

Hi Tony,

I'm in south London, so not so far away. Will post an update once I've had the chance to take a look at that piston.

Regards,

John

JohnG
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Re: Piston problem

Post by JohnG » Sun Oct 11, 2020 7:16 pm

Hello,

Further to previous posts, on removing the sump I found that it contained a lot of white metal fragments, which I assume are the remains of the bearings from number 1 connecting rod. There is a lot of movement both at the big and and the small end. I wasn't able to take the piston out yet because I couldn't remove the connecting rod cap, which seems to be seized in place (something of a recurring theme with this car...). Other connecting rods appear to be OK (no movement). I will keep trying to remove number 1 piston, in order to get a proper look at it and the crank. I am assuming engine removal etc. is now looking more likely. One thing I was wondering, if it turned out that the problem is restricted just number one piston, does it make sense just to have one connected rod re-metalled. Or are others also likely to be in need of renewal?

Regards,

John
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luli
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Re: Piston problem

Post by luli » Mon Oct 12, 2020 9:09 pm

Yes, melting of a single big end while the others stay in tact did happen to me. Usually it is accompanied with load knocks from the engine and significant drop in oil pressure. To repair you have to remove the crankshaft so that it can be grinned and that can be done only if the engine is removed from the car. Since this is going to be a long, hard and probably expensive operation it is also a good opportunity to check carefully every other aspect of the engine like the timing chain and sprockets, tappets and camshaft, rings, oil paths cleanliness, and to clean the block water ways from derbies and sediments.
Rover 10 1946 RHD
Rover 10 1947 LHD
Rover 12 1947 tourer LHD
http://lulisml.wordpress.com/

JohnG
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Re: Piston problem

Post by JohnG » Wed Oct 14, 2020 7:57 pm

Thanks Luli. Well, it will be an interesting challenge. And, as you say, a good chance to make sure everything else is OK.

TonyG
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Re: Piston problem

Post by TonyG » Fri Oct 16, 2020 6:52 pm

John/Luli,

I know that pre War cars had white metalled end bearings but I thought I read somewhere that, post War, the big ends were shell bearings. If that is the case it might be possible to renew them with the engine in situ, assuming the crank is ok. Regardless, if the crank is ok and the other ends and mains appear fine too, surely it would be acceptable to have the failed big end re-metalled to the correct size along with a new little end bearing? I know the mains have to be line bored but the ends are made to fit the crank so, assuming it’s possible to measure the big end crank diameter, it should be possible to get just one made and not take the engine out.

Clearly, a complete engine rebuild and refurbishment is the best solution but only if the rest of the car is, or will be, in great condition and intended for a lot of use. Otherwise a cheaper solution may make more sense to get the car going.

I recall my Father telling me about the time he came blasting down the A1 from Tuxford in Nottinghamshire to Uxbridge in Middlesex in his Rover 12 Tourer. It was a journey he often made and would have been pushing well over 70mph at times, which was fast in 1952, when he ‘ran’ a big end bearing and had to limp home with the engine knocking. They replaced the re-metalled bearing and fitted the piston from below to avoid taking the head off. However, to get sufficient movement on the con rod or to have working room around the crank, it was necessary to cut off a bit of the piston skirt. I’m not suggesting this is what you do but this car went on to cover many more miles, at speed! It also lived on and is now owned by another RSR member.

Tony.
Tony Gilbert

P1 12 Tourer
P2 12 6 Light Saloon
Discovery 3
Discovery Sport

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luli
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Re: Piston problem

Post by luli » Sat Oct 17, 2020 11:20 pm

Hi Tony,
The 10/12 P2 used white metal bearing to the end of the series. Usually the big end journals are in bad shape in used engines, and even more so after a bearing melt. Without grinding all the work might be in vain - the minimum is to examine the journal carefully and take micrometer measurements before deciding whats next. Removing a con rod with the crankshaft in place - even when the head is off - while laying under the car - needs a virtuoso mechanic, very hard work for dubious results. why?
Rover 10 1946 RHD
Rover 10 1947 LHD
Rover 12 1947 tourer LHD
http://lulisml.wordpress.com/

TonyG
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Re: Piston problem

Post by TonyG » Sun Oct 18, 2020 8:38 am

Hi Luli,

I agree not the best way forward and I’m not suggesting it is, only that it might be possible if necessary. It really depends what facilities are available. For some classic car owners a complete and very expensive engine rebuild may represent a terminal condition, resulting in the car being broken for parts because it isn’t economic to repair. The challenge we all face is that Rovers, in general, are worth less than other cars of similar age and quality. However, repairs are equally as expensive so a lot depends on condition and intended use.

Tony.
Tony Gilbert

P1 12 Tourer
P2 12 6 Light Saloon
Discovery 3
Discovery Sport

JohnG
Posts: 23
Joined: Thu Jul 02, 2020 5:44 pm

Re: Piston problem

Post by JohnG » Sun Oct 18, 2020 11:17 am

Hello,

I removed the number 1 piston connecting rod cap yesterday (planning to remove the rod itself later) and the crankshaft journal has some scoring (see photo). My idea was remove all the pistons and also take a look at main bearings before deciding on the next step. Woking conditions are not ideal - the car is in a single lock-up garage without much room for manoeuvre but I'm hoping that this will be viable.

Regards,

John
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TonyG
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Re: Piston problem

Post by TonyG » Sun Oct 18, 2020 1:09 pm

John,

Good luck with your endeavours and well done for getting the No1 big end cap off. I’d suggest removing the piston to see what has happened there before turning attention on 2,3 and 4. The No1 big end journal has some scoring by the looks of it but you can drop off and replace the other three to compare wear before deciding if it is beyond re-use. Similarly, take off the main bearing caps one at a time and check their condition. Personally, I wouldn’t remove pistons 2-4 at this stage if there is any chance you may want to re-use them as you risk breaking the rings etc for no real gain. If repair in situ of No1 is ruled out and you decide to remove the engine then the pistons will be easier to take out with the lump on the floor and the crank removed. No sense in struggling unnecessarily!

Another option to investigate is getting another engine. No guarantee it will be much better but you will be an expert at spotting worn out big end and main bearings if you find one to buy. A 10 or 12 engine would fit your car but be aware that pre War models had different cylinder heads and water pumps so you would need a complete unit if that is all you could find.

Tony.
Tony Gilbert

P1 12 Tourer
P2 12 6 Light Saloon
Discovery 3
Discovery Sport

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