Rover P2 - Help with some engine information

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BEW775
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Rover P2 - Help with some engine information

Post by BEW775 » Wed Jun 23, 2021 2:45 pm

Hi,

My car is a 1939 Rover P2 12hp which I have recently purchased. I think it has a 1936/7 10hp engine fitted. I have a couple of questions please:

(i) I can't find the engine number. The number on the V5c starts with a 6. Am I correct in assuming that is for an engine produced in 1936 and the correct engine for my car should have a number beginning with a 9? Could someone help me with the engine number location please?

(ii) The engine fitted smokes quite a lot, certainly too much to use on the road. Apparently it stopped while being driven in 2000 and the garage entrusted with the repair advised it would need a new piston. I am told they struggled to find a replacement and the car has smoked since. I would normally assume stuck rings etc, but it looks more likely that there is an issue with the repair work. The compressions are 140psi cold. I have been reading Luli's very informative articles and I believe (if I have understood correctly) that if I do have the 10hp engine fitted, I could rebore it and fit a set of 12hp pistons. Is my understanding correct?

Thanks

Anthony

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luli
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Re: Rover P2 - Help with some engine information

Post by luli » Wed Jun 23, 2021 9:17 pm

The engine number is on the driver side engine support "wing". See picture.
140 PSI is surprisingly high. Check valves.
Pistons and rings supplier is F/ W. Thornton and sons. There is also an Australian manufacturer. You can also get them from Mikes and Freddy Boulton.
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Rover 10 1946 RHD
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GOY189
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Re: Rover P2 - Help with some engine information

Post by GOY189 » Fri Jun 25, 2021 9:11 pm

The 10 and 12 share the same block, so it is common to bore the block out to take 12 pistons. With a 10 Cylinder head there is a useful increase in compression ratio and better performance.

Mike

BEW775
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Re: Rover P2 - Help with some engine information

Post by BEW775 » Thu Aug 19, 2021 3:15 pm

Firstly, thank you both for your replies and apologies for not replying sooner.

Since my last post, I have received all the paperwork relating to the car. There is a lot of lovely history including a book that the preious owner started in 1969 that details everything spent on the car up to 2002!

I now know that the engine is a 1937 Rover 10 engine with the earlier 6 port head, which was fitted to the car in the early 1970s. This engine failed in 2002.

In this history is the bill from an engineering firm who worked on the car in 2002. They have replaced the pistons, rebored the block and fitted a liner to one of the bores. They have also replaced one of the valves, the small end bearings and cleaned up the head. They had the car for 2 years but were unable to stop it smoking. It looks like the car hasn't been used since it came back from the engineering firm.

Mike at Meteor spares suggested (and he was correct) that holes in the rocker shaft may be in the wrong position causing the engine to smoke.

I have now removed cleaned and refitted the rocker shaft, with the holes in the correct position. The engine oil looked very clean but smelt of stale petrol so I have drained and refilled with Comma 20w50 mineral oil. I have some Penrite 20w60 which is what they suggest for the car, but I am reluctant to use it until I know if the engine is usable! It doesnt smoke as much, but it is still fairly bad and it couldnt really be used on the road.

I popped a camera into the bores and they look ok (although I am not sure what I was expecting to find!!) I have also removed the inlet manifold and found that there is a lot of oil on the back of the valves, so it looks like I still have too much oil getting to the top of the head.

I was wondering if there should be a restrictor of some type that limits the oil feed to the rocker shaft, that has been lost during the engine work? Alternatively, could the oil pressure be incorrectly set and therefore supplying to much oil to the rocker shaft?

I am trying to get an idea if this engine will work for me, or if I would be better looking for a correct Rover 12 engine with an 8 port head.

Any suggestions would be appreciated.

Thanks, Anthony

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luli
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Re: Rover P2 - Help with some engine information

Post by luli » Thu Aug 19, 2021 6:26 pm

I once saw an engine with a tap on the pipe feeding the oil to the head...
If you oil pressure, when hot, is higher than 30 at 30 mph you can reduce the pressure by the oil pressure adjuster below the distributor. I doubt if this is the solution. Try to run the car for a while, good chance that it will cure itself.
Rover 10 1946 RHD
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TonyG
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Re: Rover P2 - Help with some engine information

Post by TonyG » Fri Aug 20, 2021 7:40 am

Hi Anthony,

Until the 1980s it was common practice to run cars in when new or after an engine rebuild. It sounds would be worth doing that with yours before deciding the engine is scrap.

Make sure that the engine timing and carb set up is correct and that you are using new clean fuel. When running rich or with choke out, your engine will smoke so don't mislead yourself.

However, after some hours of running, if the smoking has not reduced at all and it really is blue oily smoke, then the cause can only be one of two things; either the oil is coming up the bores or down the valve guides into the combustion chambers. In either case, it would be very unlucky if all four chambers had the same problem and I'd have expected to see one or maybe two of your plugs oiling up and maybe starting to mis-fire.

With a recon engine one would hope that the oil control rings are in good shape but they need to bed in- hence running it for a while. It's possible that one was damaged when fitted but then only one plug would oil up.

It could be that the valve guides are worn but unusual that they all become bad at once. Modern cars have rubber oil seals on the valve stems to reduce oil consumption. So, again, check that it isn't just one plug oiling as this could point to one badly worn valve guide. This brings me to the final thought that the new valve fitted may not be of the correct size, allowing oil to get down the guide too easily.

To conclude, my guess if it is burning oil on all four plugs is that the engine needs to be 'run in'. But if it's worse on just a single plug, check the new valve. Failing that, you could get another cylinder head and try that first. Rebuilding one of these engines isn't cheap so worth doing that before giving up on the one you have.

If you do get a later 12 engine, I'd consider buying the 10 from you to keep as a spare block for my cars, but I don't think it will come to that!

Good luck.

Tony.
Tony Gilbert

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

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