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MG MGB Technical - oil pooling on piston

Any answers on this... recon engine 2k ago run in using all the normal advice smokes blue on start up, then settles down after a run puffs the odd cloud of blue smoke almost like someone is squirting a small amount in cylinder . compression all equal wet and dry , all plugs apart from no2 seem normal no2 always sooty I have just put a catch tank from the breather pipes as they seemed very wet with oil, but noticed tonight no 2 piston has a small pool of oil on the crown The engine was fitted by someone who really understands mgs so i am really confident in the rebuild , Is this a head off job at the weekend any ideas would be appreciated

Richard H
Richard H

Richard-
With oil puddling on a piston crown, it sounds as if you have a bad valve guide that allows excess oil to leak past the intake valve stem. The quickest way to test for this is to drive the car on the road, downshift, close the throttle while the engine speed is high, and then look back to see if the smoke appears. If it does, its because with the throttle closed, vacuum inside the ports is at its highest and the higher pressure inside the valve cover forces the oil down the stem of the intake valve.
Steve S.

A bit of oil drainage from the valve guides is not unusual in these cars.
Stan Best

It's possible that a valve seal was damaged or inadvertently omitted during installation of the valve spring, and if the valve guide clearance is tending to the looser end (for that valve), then that could explain it.

It's possible to replace a valve seal with the head on.

Wayne
Wayne Pearson

Thanks so far for all your replies, I really want to try and work through this before i have to book it in , so this weekend its rocker box off maybe carbs and manifild to see if any signs of oil ect of then crankcase covers just for good measure .I will keep you updated

Regards
Richard H
Richard H

Wayne - How do you replace a valve stem seal with the head on?

Richard - if you are only get oil in one cylinder then the breather is unlikely to be the culprit. I vote for valve stem seal leakage too, but it is not inconcievable that none were fitted. The o-ring types don't do much anyway!

Neil
Neil22

I was wondering that my self i have looked at all the manuals but cannot find away to change taht seal with the head on, but i am sure we are about to find out
Regards Richard H
Richard H

You can replace the stem *seal* by removing a plug, feeding in loads of thick cord with the piston at the bottom, then turning the engine carefully so the piston pushes the cord up against the valves to hold them up, then remove the collets - with a little ingenuity!

You can even replace the valves and guides with the head on if you do what Bugatti did and work from below, some of his engines had a one-piece head and crankcase!
Paul Hunt 2

PS. Leave the free end of the cord hanging out the plug hole :o)
Paul Hunt 2

That's what i love about this site what a great idea ! its brilliant and simple, whilst driving home from work tonight i wondered if anyone had marketed some sort of automotive endoscope with a blue-tooth facility so you could hook up to phone or laptop, you could do so much investigatory work on an engine with one of these devices and the technology is there but maybe i am missing the point. After all its great hiding in the garage at weekends with the other woman ! spending well earnt £s and $s keeping her in good health

Kind
Regards to all

Richard H
Richard H

Paul - can you expand on 'a little ingenuity'... especially with double valve springs!
Neil
Neil22

Look at this site, http://www.mytoolstore.com/kd/kdengi13.html for some ideas. I have the KD 2078 and find it works fine with double springs. I was actually thinking of a lever-type compressor when I posted before, using the rocker arm shaft as a pivot.

Wayne
Wayne Pearson

Years ago I watched the local Olds dealer do this to my car. They used a sparkplug adaptor to connect a compressed air line to the cylinder. The air pressure holds the valves in place. They had a tool that connected to the rocker studs to compress the springs. It was a V8 and all the seals were changed in an hour.
John H

Ahh - for 'a little ingenuity' read 'a very useful tool'...!
Neil
Neil22

"so you could hook up to phone"

A friend once called me from Ireland with a very bad misfire on his V8 and proceeded to hold the phone by the engine so I could hear it. All I could hear was a whole lot of mechanical noises and not able to pick anything out, partly because it was monaural and partly because I'm not in the habit of noise diagnosis by phone so I didn't know what were the right noises and what weren't!
Paul Hunt 2

This thread was discussed between 13/09/2007 and 15/09/2007

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