Distributor advance query???

[nomad]

On a 73 MGB engine pinging under load is a problem. It seems like the advance curve is way off from the factory. Have others experienced this? What is the cure? Vacuum advance just failed and pinging under load ceased. Engine seems to have more power in the mid range but I am sure fuel economy will suffer. Ideas Pls!!
KA.

 

[Stewart]

Best thing to do is have it rebuilt and curved to match your engine. Jeff at advance distributor is great I've had 3 distributors done with him and they look better than new and work way better than new. He's in MN and his turn around is usualy quite quick.

 

[nomad]

Thanks, I was asking for a friend who bought my MGB. The advice is pretty much the same as what I gave him. Do remember seeing the advance curve for these engines somewhere and it seems to be perfect for pre-ignition.
KA.

 

[MGB922]

You can test a vacuum advance diaphragm by putting a vacuum pump on it. Should be able to hold 22 lbs but if it's blown you'll know it. There is also centrifugal advance weights in the distributor that are control by 2 springs. I've heard of them breaking before and this would cause your advance to react too quickly. Make sure your points are in good condition then check the dwell. Bad engine vacuum can cause a pinging also. Put a gauge on a manifold port, see what it doing. A Chilton’s manual has descriptions on how to read it. What does your timing light tell you. Is it steady of fluctuates. If it's fluctuating the tensioner may have gone bad or timing chain worn. Did it jump time? A timing light should tell that. Is you carb(s) set right; mixture, idle speed, as these can cause carbon buildup. How is the gas? Are they putting more alcohol in it. They didn't have a lot on alcoholic gas pumps in 73. Go with premium for a while and run her on the highway to clean out some carbon. I've used the water in the carb trick to clean carbon out of the chambers. Too much carbon can cause pre-ignition/pinging.

I've seen a lot of things that can cause timing issues or pinging from a weak rotor button on a distributor cap to a missing keyway on the timing chain crank gear

I'd diagnose first before changing parts. Hope this helps.
Tim

 

[PAUL161]

I've used the water in the carb trick to clean carbon out of the chambers. Too much carbon can cause pre-ignition/pinging.
Tim

Tim, your telling your age when you talk about spraying water in the carb/s! That was a great trick on Model A Fords which would carbon up using bad gas and running too rich. The carb on a model A had a mixture control on the passenger side below the dash and many times the driver would start the engine with it set on rich and forget it. The plugs would foul up with carbon and the water trick would clean it out.