Smoking rebuild engine

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Stef
Posts: 3
Joined: Thu Jul 23, 2020 8:08 pm

Smoking rebuild engine

Post by Stef » Fri Jul 24, 2020 8:13 pm

Hello,
Some years ago I bought a Rover Speed 14 hp 1934 and the engine was running but was burning a little oil.
So 2 years ago I decided to rebuild the engine. Al bearings renewed white metal ,new valves and guides,new cylindersleeves
Because there was cooling water leaking on the pistons and I even found NOS cosmo pistons.
These pistons have a split skirt, 2 compressionrings and 2 oil rings ( piston pin in the middle of these 2 oilrings.)
This job took me almost 2 years. Rebuilding prewar engines is getting almost impossible here in Belgium.
Now the engine is running very nice but theres a big problem. The engine pumps up oil and is smoking like a smoke machine.
When I rev the engine the neighbours think that my garage is on fire! It is not possible to drive this car on the road!
When I turn out the spark plugs then theY are all covered in oil. I use 15 W 40 oil for running in the engine.
Running the engine cold or hot gives the same smoking problem. Only when restarting the engine when hot the problem is gone
Just until i rev the engine and the smoking problem gets back. There is no water leaking into the oil and no exhaust into the cooling system. The engine ventilation is normal .The problem comes from the pistons I think.
Does someone had the same problem with cosmo pistons?
Kind Regards, Stefaan

digcot65
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Joined: Sun Apr 19, 2020 1:34 pm

Re: Smoking rebuild engine

Post by digcot65 » Sat Jul 25, 2020 12:40 pm

Have you checked to make sure the air breather is not blocked causing pressure in the crank case

RobHomewood
Posts: 194
Joined: Tue Oct 22, 2013 8:04 pm

Re: Smoking rebuild engine

Post by RobHomewood » Sat Jul 25, 2020 7:06 pm

May I ask a rather basic question? If the breather tube were blocked would it show increased oil pressure on the gauge? It just struck me that could be the cause of my smoking but the oil gauge is rock steady at 30 psi.
Rob

Stef
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Joined: Thu Jul 23, 2020 8:08 pm

Re: Smoking rebuild engine

Post by Stef » Sat Jul 25, 2020 11:04 pm

The air breather is open and there is no smoke coming out. Engine has good compression.
The more I think about the smoking problem the more I think that the headgasket is bad.
This would explain the smoke but why are all sparkplugs covered with oil?
The gasket i installed was just a thin cupper plate. The old one was double cupper plate and asbestos in between.
Wrong gasket?
Kind Regards, Stefaan

TonyG
Posts: 147
Joined: Mon Sep 07, 2015 4:38 pm

Re: Smoking rebuild engine

Post by TonyG » Sun Jul 26, 2020 8:12 am

Stephan,

I have no experience of the 14 engine but the 12 has split skirt rings also. Attached is a picture of a piston removed from my Tourer. Is this similar to yours and, if so, did you refit the pistons with the rings in the same order? I ask because it appears that the two oil control rings are different in function but possible to place in wrong order or upside down. Also, I suspect that the upper of these two rings has a duel purpose for compression and oil control so possibly fitted at 120 degrees to compression rings, but that is a pure guess on my part.
Good to discount the possibility of the rings and hope this helps.

Tony
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Tony Gilbert

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

GOY189
Posts: 461
Joined: Sun Oct 19, 2008 5:08 pm

Re: Smoking rebuild engine

Post by GOY189 » Sun Jul 26, 2020 10:55 am

Hi Stef,
In addition, were the liners honed so the rings could bed in, before fitting the new pistons? It does sound as though the rings could need further investigation but as you say, compression is fine. Have you considered that the oil may be reaching the combustion chambers from the top (down the valve guides?)
Hope this helps

Mike

RobHomewood
Posts: 194
Joined: Tue Oct 22, 2013 8:04 pm

Re: Smoking rebuild engine

Post by RobHomewood » Sun Jul 26, 2020 5:36 pm

After digcot65's comment (thanks for that) about checking the crank breather I did just that on mine. I took the hose off and the engine plate outlet first and they looked clean. I pushed a wire through the lower tube OK (still in situ) but when I tried a small hose it got stuck. There was definitely an obstruction but not sure whether it was a total blockage. This was not where my instincts suggested there might be a problem in a virtually straight piece of pipe! I took the pipe off, applied plenty of gunge cleaner to soften the blockage and then pushed the debris out with a fuel hose. After flushing with paraffin it looked pretty clean. I have refitted it but when started I still got the usual deposit of soot on the floor from the exhaust. However maybe the engine needs time to clean itself out so I still have high hopes this has abated my smoking problem.
Rob

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

Re: Smoking rebuild engine

Post by TonyG » Mon Jul 27, 2020 12:05 am

Rob,

I forgot to say in previous post that crank case compression won't affect oil pressure. The crank case gets pressurised by the pistons moving up and down. If you like it's the opposite effect of cylinder compression and nothing to do with oil pressure.

Regarding the sooty exhaust deposits you are getting; I get these when first stating up and feel it is the result of condensation in the silencer boxes. The soot is washed out and gets blown onto the ground but appears ok oncebhot.ive given up worrying about this as all ok once hot.

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: Smoking rebuild engine

Post by luli » Mon Jul 27, 2020 7:42 am

Bad head gasket would show up with babels in the water, water disappearing or water in the oil. If these symptoms don't exist the head gasket is OK. I would suggest just let it run for few hours, using thicker oil. The engine may run in and cure itself.
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Stef
Posts: 3
Joined: Thu Jul 23, 2020 8:08 pm

Re: Smoking rebuild engine

Post by Stef » Mon Jul 27, 2020 8:32 am

Hello Tony,
I have a set nos 14 hp pistons witch are the same split skirt pistons as the one in your picture.
Only the oil rings are opposite installed. So we can be sure that the oil rings have no top side .
All guides and valves are new and the company who rebuild the engine has a good reputation.
The engine has new cylindersleeves. Before the rebuild the engine was overbored and there was water leaking into the cylinders!
The engine burnt oil also. The smoke the car makes now has not the typical oil sent. So the exhaust. Smoke also contains water.
The car smokes the same way as a car with a broken head gasket.
The engine has run 30 minutes and the smoking problem stays the same. Excessive oil on the pistons when rebuilding the engine
Should be gone. I will take of the valveblock and check the head gasket and look if there are no cracks in the valveblock.
They checked the valveblock with pression after they rebuild it and they found a crack in one hole for a fixing stud.
They repaired it and there was also frost damage in the engine block. That crack was lso repaired.
So the engine had a total rebuild And now its smoking like hell !
Kind Regards, Stefaan

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