MGB Register Forum

Ta for that Vic. When I've got the car running right, I'll lay the car up next month, and look into the head conversion.
I've done the carbs this morning, and I'm happy that they are somewhere near.
However, the acceleration is not up to scratch, so I checked the vacuum advance. When I suck hard on the pipe there is no movement at the distributor base plate. In the past (distant!) when I have done this there has been a movement there advancing/retarding the ignition. Static timing is set to 5 degrees btdc on account of the unleaded. Should there be movement on sucking.
Dave

Yes, looks like the vacuum advance has had it. Contact the Distributor Doctor with the number of the distributor for a replacement vacuum unit. He will probably want the old one.
The correct distributor number for your car is 41610. This one was fitted only to rubber bumper cars.

Car running well this afternoon despite the vacuum advance(retard?) problem. Distributor off tomorrow for a shufty. Rheostat now out and panel lights working (very dim!).
Thanks all.
Dave

Dave, what petrol do you put in your MG? I use Shell V Power. If you use a higher octane petrol you could probably time statically at 10 degrees. A test is to floor the throttle in top gear at low revs and listen for pinking and if it occurs gradually retard the ignition until it stops.
The vacuum advance is only operative at cruising speed on a light throttle for economy. Peter Burgess a respected B engine tuner advocates disconnecting the vacuum. I'm going one step further and have sent a 45D4 distributor to the Distributor Doctor for conversion to a 43D4 which has no vacuum advance unit. I think the timing on yours is too retarded.

Dave,
I use Shell Niitro (previously simply called V power or Tesco momentum + castrol valvemaster plus with original block,head & original HIF 4 carbs.
(With 123 distrib set up some 7 years ago with the timing unchanged from then). The car pulls well & does not run on when turning off.As said earlier running on can be caused by the degree of advancement set ,but also if your idle setting is a little high.
I am not surprised that you have discovered how poor the instrument lights are - hence the joke is why would you need a dimmer?
The orig bulbs blacken with age +accumulated dust on the green filters (they are on mine) in the guages.
You can get warm white LEDS to replace them if you want to keep the original hue. If you get the shorter type then you don't have the fiddle of having to remove the green filters. (If you remove the filters then you may wish to get coloured LEDS to create an original effect.
Cheers, Charles

Vic and Charles. I use the noname stuff ordinary unleaded from the villlage garage. Nearest "super" unleaded is 26 miles away. I'll take a trip up there and get a tankfull today or tomorrow and give it a whirl.
I'll be laying up at the month end, so I will leave the vacuum advance alone until then.
Incidently, my car was first registered 40 years ago today! So when I relicence in April next year the tax will be free. I paid £140 for 6 months tax a few days ago. I expect I'll be lucky to get £100 back when I lay up from 1st November.
Regarding panel lights, they are so dim that they may well have been working all along!
No evidence of pinking just now, so I'll try advancing a bit at a time and see How I get on.
Thanks for your help Charles, Peter and Vic, and I'll update as necessary.

Don't forget Dave that you'll have to renew at a Post Office next April as it's a change of taxation class and you can declare MOT exemption at the same time on form V112 if you want.
It's best to use premium unleaded.
Because of emissions regulations at the time your car was manufactured the vacuum advance feed is from the inlet manifold which gives vacuum advance on tickover which is totally unnecessary. The distributor 41610 was fitted solely to rubber bumper cars for that reason.
Try advancing the ignition and disconnecting the vacuum advance and block off the outlet on the manifold.
. Vic

Quick update. Car running well now after carb check out and ignition timing check out. I 'm going to get a good few miles on it before the end of the month, and then lay up to do the axle oil seals and a thorough check so that I can start driving next April.
Even the running on has now ceased!
Forgot to mention it's going to be my main daily transport
Dave

Dave,
That's good news. Enjoy!
Cheers, Charles

Small mishap today. Heater valve leaking, so new one ordered and old one reomoved. I thought while the heater valve was off, I would check out the vacuum advance not working, so out with the distributor. Dismantled the plates, and all seemed fine. Sucked on the vacuum pipe and loads of movement. Put it all back on the car, and gave the pipe a suck. Zilch movement!. I'd read somewhere about the possibility of a screw fowling the mechanism. Sure enough another washer on the points fixing screw, and bingo it's fixed.
edit. What's all this * business? It's a fastener, not a sex function!
edit. What about scroo?