My brother has a cherished 1978 MGB that he has had since 1979. It never ran as well as his previous 1970 model.It ran on a lot and was slower due we understand to modifications for the American market. A couple of years ago he had the engine rebuilt and had it mildly gas flowed and the compression raised. Since then it has been used only for about 2000 miles per year. It pinks terribly unless the ignition is very retarded. He has been told that a thicker head gasket can be obtained that will lower the compression and solve the problem. Any ideas on how to stop the pinking and make it run sweet gratefully received.
I told him that there was bound to be an MGB expert in the Back Room
Cheers
Peter
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Peter,
Dad owned one of the nicest MGB LE models about 6 years ago. I seem to remember he had to be very careful about timing settings. And wasn't there an advance restrictor capsule in the hose from the manifold to distributor? Also I think you could get a replacement distributor with a more mild advance curve to help.
But you say he has had the head modified for greater compression anyway. These are never going t be a ball of fire, or handle on rails if you do get them going. I would refit a standard compression unleaded head. They are prone enough to pinking/running on without this owner induced help.
I am no expert on these but just some thought for you as there are no other overnight posts.
Must get out early to finish the brake overhaul on my 40yr old Land Rover project, I'll look later at what the experts do tell you.
David
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Peter,
David is quite right in that raising the compression can be counter-productive. However, here a few tips. The main modification for USA emissions on later Bs was the introduction of 'direct' vacuum advance (ie. the pipe from the distributor connected to gull manifold vacuum) - this tended to give a very lumpy tick-over and spoil initial acceleration as the basic timing setting was also retarded. We used to be able to buy a kit to re-route the vac take-off back to the throttle butterfly area on the rear carb (ported vacuum), so that the vac advance only operated on light throttle, but this kit is , to my knowledge, no longer available. Fitting earlier carbs is another way to achieve ported vacuum advance. Next best option is to simply disconnect and blank the vacuum advance at source. On a standard head I would then reset the ignition to 15 degrees BTDC @ 1,000rpm, as per the earlier model -- performance + drivability restored, but mpg not quite so good.
With a higher compression you may still have a pinking problem. Assuming everything else is spot on, especally making sure the mixture is not too weak at any point in the rev range, a modified distributor may be the only answer, giving a reduced amount of advance. You would need to compare the advance curve against the current spec, and some experimentation may be necessary (rolling road is best for this).
Lastly, have you tried Super-Unleaded, or an octane booster additive ?
Regards + Good Luck, Adam
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This is a problem well known to the MG Car Club. Join the club and get the answer (which certainly isn't to drop some metal pellets intot he fuel tank).
HJ
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hj,
Hope you don't think *I* was suggesting the dreaded pellets/fuel catalyst, as I feel as strongly about them as yourself. I was referring to either one of FBHVC approved products (Millers VSP / Castrol Valemaster Plus) or a straight octane booster such as the Redline product.
Regards, Adam
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Thanks to David, Adam and HJ. I will pass on your advice and post up the results. However the speed my brother gets round to things it could be a little while
Cheers
Peter
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Adam, I wasn't replying to you. I was replying to Peter who posed the question in the first place. The best way to respond to another contributor to a thread is to identify them because you could find your reply coming in a few answers down the thread from the contribution you wanted to reply to.
HJ
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