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MG MGB Technical - Missing cylinder

Hi all,
Have just finished a rebuild on my 1970 MGB GT, and after a few trials have got the car started and running OK. Timing is now "spot on", tappets adjusted, sparks cleaned and carbs set up as per the handbook.
The car now ticks over at a steady 900rpm and sounds good up to 3000 rpm (which is as far as I have gone)Pulls well and smoothly - no sign of pinking.
Just one problem, now and again cylinder 2 just drops out - running fine one second the next the cylinder drops out - keep going for 2 minutes and the cylinder comes back in. Allways number 2 cylinder (I have stopped and removed the leads and confirmed this).
Nothing I seem to do stops it from happening - I have removed and recleaned and reset the spark plug, put them back in different cylnders, cleaned the distributer cap and rotor arm, rechecked the gaps (I have noticed that the shape of the distributer shaft results in a slightly smaller gap on number 2 cylinder, but the difference is miniscule) everything I can think of.
Any ideas anyone?
Mike
Mike

Have you changed the lead to No2?
Regards
Roger
Roger T

Try the easy things first. Like Roger said, "swap the leads". If this does not correct the condition, it is possible that you have a valve sticking in the guide. You did not say that you had any head work done with your rebuild.
Good luck,
John
mgdoc

The title of this thread reminds me of one of the rib-ticklers from Quantas maintenance logs:

Pilot report: No.4 engine missing.

Maintenance fix: No.4 engine found on right wing after short search.

I had a similar problem on a midget 1500 recently after changing the head gasket. The one cylinder (located by removing the plug leads from the distributor cap one by one) would stop working when it got up to temperature, but a timing light on that lead (which I had swapped with another cylinder) flashed as normal, and there weren't any explosions in the exhaust which I would have expected. I began to think that maybe it was an exhaust (because there was no chuffing in the intake, only the exhaust) valve sticking, but using the adjustable timing light on the appropriate plug lead in a darkened garage I could turn the adjuster and 'freeze' the valves anywhere between fully up and fully down, and all the valves were the the same. Then all of a sudden it stopped and didn't return.
Paul Hunt 2

PS. Changed plugs a couple of times but still no difference.
Paul Hunt 2

Maybe try opening the points gap by .002" (on the 3 higher lobes)?
Tom

Thanks for the comments guys,
I think I found the problem.... the injector on the carb on that side was leaking air. I have replaced it and the problem now seems to have gone....
Now quick follow up - whats the best and easiest way of balancing the carbs?
If someone can point in the direction of a guide that would also be good.
Thanks

Mike
Mike

You might like to have a look at http://www.mgb-stuff.org.uk/wn_fuelframe.htm and click on 'SU Carbs' and 'Setting-up'.
Paul Hunt 2

This thread was discussed between 17/09/2007 and 25/09/2007

MG MGB Technical index

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