D612 PNT One of these days...

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Re: D612 PNT One of these days...

Postby All That Glisters » Sat Apr 01, 2017 6:25 pm

A (very) wet air filter?

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Re: D612 PNT One of these days...

Postby fozzza » Sat Apr 01, 2017 6:50 pm

Was there moisture in the breather side being fed back to the carb or was there water residue in the recently cleaned fuel tank :?:
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Re: D612 PNT One of these days...

Postby ACourtney » Sat Apr 01, 2017 11:27 pm

No one has got there yet. The clues are all in my previous posts, but it may be worth reading them all through from the start!

As I said the problem was a bit of a puzzle: The smoke was caused by a fault, which in turn was caused by another fault, which was due to something else again. When I found the cause I was able to get rid of the smoke immediately, but a longer term fix took more time.... Now I've made it into a riddle!

I will repeat the biggest clue again, which was that the smoke only appeared when the car had warmed up fully.

Roy (Fozzza), I'm afraid that I will have to add you to the exclusion list. When you visited me the other week I was doing some work on Desmond's Gold Coupe to make sure that the problem would not occur on his car. I can't recall if I mentioned the connection to the smoke to you, but you could easily put two and two together to work it out.
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Re: D612 PNT One of these days...

Postby Hans Efde » Sun Apr 02, 2017 8:32 am

You had washed the car and sprayed water into the muffler. Or it has been standing outside and rain had gone into the last muffler.When heated t turns into steam and comes out.
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Re: D612 PNT One of these days...

Postby ACourtney » Tue Apr 11, 2017 8:45 pm

I've had a busy time since I last posted. Having visited Kent in the East and Saltash (nearly Cornwall) in the West, with various stops in between, over the space of seven days. Anyway, enough of excuses.

I'm afraid that nobody has hit the right answer yet. As I have indicated, it was a very complicated fault. I discovered the cause almost by accident when investigating one of the suggestions mentioned above.

In between the car failing the MOT and my finding the cause of the smoke, I removed the cylinder head and had it converted to run unleaded. Chris had wanted to have the head converted, but originally we had decided to postpone that until the engine had been bedded back in. However, the smoke problem combined with an increase in the oil seeping out the back of the head gasket made us think again. The smoke might just have been caused by the gasket failing. Usually when a head gasket fails the combustion gases get into the water and cause rapid overheating.

I once had a problem with a Ford engine that was burning oil and it turned out that the failing gasket was acting like a one-way valve: On the induction stroke the gasket would allow oil to be sucked into the combustion chamber, but on the compression stroke the gases would get in between the layers of the gasket and cause it to expand and seal itself. So never rule out anything until you have thoroughly investigated it.

On Chris's engine there were signs of combustion gases starting to seep under the gasket, as well as signs of the oil seeping out of the back so it was clearly time to replace it. However, there was no sign of any water getting into the combustion chamber. Unfortunately, I can't find the photo that I took of the gasket, but here is one of top of the block after I had removed the head, gasket and studs:
Image20151205_111319 by Alistair Courtney, on Flickr
One comment of note is that the pistons were wet with fuel. The studs were also showing signs of aging, with rust on a couple and soot on a couple more.

Chris's engine is an MED built 1380cc engine with larger inlet valves, a gas flowed head and nice set of roller rockers - as seen after refitting:

Image20151205_152419 by Alistair Courtney, on Flickr

One thought was that the smoke might have been due to the head becoming porous where the inlet ports had been opened out. So we figured that the first thing to do would be to have the head pressure tested.

I took the head to Rob Walker engineering just down the road at New Yatt, near Witney - http://www.robwalkerengineering.co.uk/
Rob used to run the Oselli machine shop back in the days when they were one of the leading A-series tuners and is extremely helpful. He won't suggest that you have work done if you don't need it and he was very pleased to report back to me that the head was leak tight. He also reported that the head face was perfectly flat, the valve guides were in good shape and the exhaust valves fitted were of a hard enough grade so that only work required for the unleaded conversion would be fitting hardened valve seats. After a quick chat with Chris we also got Rob to put the head through his chemical washer so that it was thoroughly clean when I came to put it back on.

So whilst Rob got to work on the head, I ordered a new head gasket and a set of uprated head studs.
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Re: D612 PNT One of these days...

Postby ACourtney » Mon Apr 17, 2017 4:45 pm

Having got a nice clean cylinder head back from Rob Walker Engineering -

Image20151205_140320 by Alistair Courtney, on Flickr

Image20151205_121533 by Alistair Courtney, on Flickr

I thought that I should clean up the top of the block to match. Many years ago, when I was racing an MG Midget, I bought a load of non abrasive, nylon mesh, 2" cleaning discs for just such a job. I still had half a dozen of these discs left over and in combination with my 2" air sander they made light work of the job (when they weren't flying off around the workshop!).

Image20151205_113144 by Alistair Courtney, on Flickr

After finishing the job, two of the discs were completely spent and two were missing in action (I found one several months later, but one is still unaccounted for) so I now only have three usable discs left. Searching on the internet, I could only find abrasive cleaning discs (3M Scotchbrite, or Strip and Clean type discs). The abrasive discs are not a good idea for cleaning the mating surfaces of the block and the head as they can wear away the metal. So if anyone knows of a source of the non-abrasive type cleaning discs I would be keen to hear where I could get some more from.

With everything cleaned up, it was then a case of fitting it all back together and torquing down the head. For those interested in the details, the new head gasket was Minispares' GEG300 Copper head gasket for large bore engines and we also went for their competition head stud and nut kit and the stainless steel exhaust stud set. With it all back together, and torqued back up I just had to recheck the valve clearances and then refit the rocker cover, before refitting the exhaust and inlet manifolds. Finally, I could refit the water piping and top up the coolant level.

The engine fired up fine and ran perhaps a little smoother than before. Once the engine had warmed up sufficiently for the choke to be pushed back in, the exhaust appeared to be smoke free. However, within five minutes the white smoke had reappeared.
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Re: D612 PNT One of these days...

Postby Rich » Mon Apr 17, 2017 5:23 pm

You aren't burning brake fluid from a leaky master cylinder are you?
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Re: D612 PNT One of these days...

Postby ACourtney » Mon Apr 17, 2017 7:19 pm

Rich wrote:You aren't burning brake fluid from a leaky master cylinder are you?


No. I had tried taking off the vacuum line and the oil breather pipes, but they made no difference.
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Re: D612 PNT One of these days...

Postby Alan D. » Tue Apr 18, 2017 5:21 pm

Could it be a porus block?
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Re: D612 PNT One of these days...

Postby benofbrum » Tue Apr 18, 2017 10:34 pm

One of the pistons seems to have much more carbon deposited on it than the others. Hairline crack or porosity in that piston?
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