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MG MGB Technical - really quiet tappets

My brother-in-law has recently bought a rather nice mgb roadster, a 77 model I believe, which has been rather nicely converted back from rubber bumper to chrome bumper. It has a 5 bearing engine.

At first it ran reasonably well, although it was throwing out a bit of black smoke, but after being stood for a week or two, the next time out it was running quite badly on 3 cylinders and he asked me to have a look at it. (I have an MGA with a 3 bearing MGB engine fitted.)

I pulled off the plug leads one at a time and although the 10,000v through my fingers was a bit distracting, I managed to find out that No 2 cylinder was not firing.
When we checked the plug you could see that it was oiled up and had not been firing.

I fitted one of my spare plugs and this did improve the running although it was still very lumpy and smoking quite a lot.
So I decided that it could do with having the mixture adjusted a little weaker.
I screwed each of the carb jets up by just 2 flats and there was an immediate improvement in the tickover and the engine was much smoother.
It accellerated much better too with much less black smoke.

Then listening to the engine I noticed that there was almost no tappet noise which worried me a little as the tappets on my MGA are very distinctive.

The car does have an alloy tappet cover but so does my MGA.

Should the MGB tappets be as noisy as they are on my car or are the 5 bearing motors much quieter.

I am looking out my feeler gauges and gunson quick adjust as I type this!

Cheers

Colyn
Colyn Firth

My (quasi-recently rebuilt) engine was always pretty "tappetity". I recently refaced the rocker pads -- not done as part of the rebuild -- and readjusted the valves and it's now pleasingly quiet. It only takes a few thousandth's wear to make a few thousandth's maladjustment on the valve lash and that can have a noticeable effect on noise.
Rob Edwards

Agreed with Rob. Wear can, and generally increases the 'Tappity' noise. But when one does not hear it at all, one worries are the valves closing fully? Might got noiser of late, so I checked then sure enough a little too open. But, back to the question B's do tend to be a bit noisy isn't that right? Mike
J.M. Doust

I always worried about the sewing machine noise my B made, but have since found it it very normal.
Bruce Cunha

MGB's are always a bit tappety, alloy cover or not! Probably valve seat recession causing the clearances to close up. Get those feeler gauges out and re-set them and then check frequently to see how quickly they close up.
Allan Reeling

A side note is that the B Series engine is incredibly responsive to proper valve adjustment. The engine loves to breath, and properly adjusted valve lash can make engines which were 'off' feel very powerful in comparison.

warmly,
dave
Dave Braun

This thread was discussed between 03/05/2012 and 05/05/2012

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