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MG MGA - Valve Tapping

Hope to get some help here, I have a 1958 that has about 20K miles since I rebuilt. It runs and starts fine but after it gets warmed up and I start to go up any type of incline while in 4th gear I start to get a hell of a tapping noise. It stops when I go downhill so it appears it is only happening while the engine is under a little bit of a load. I also get the sence it is running sluggish. I adjusted the valve and it only appears to have made it worse.
Thanks for any suggestions
WMR Bill

Pinking? Ignition too far advanced?

Steve
Steve Gyles

Definitely pinking.
Art Pearse

My first car had a control on the dashboard to manually retard the ignition which was designed to cope with occasional poor quality petrol that was found just after the war. In the 1960s petrol quality had improved and I only ever used the control to prevent pinking when going up hills in top gear.
The onset of frequent pinking was usually an indication that the engine needed a decoke. In those days I recall doing decokes every 6000 miles or so to reduce the pinking and improve engine power.

Perhaps after 20K miles the engine needs a decoke especially if the timing doesn't look to be out...............................Mike
m.j. moore

Check the little plastic cam on the points. If that has worn, it will have the effect of advancing your timing, which will cause the pre-detonation, particularly under load, as well as making the car sluggish.
dominic clancy

That sounds odd. If the rubbing foot on the points wears down the points gap diminishes, dwell increases, points open later and close sooner. Later opening points means retarded spark timing, not advanced. Always set points before setting timing.
Barney Gaylord

Bill, could be the exhaust manifold gasket, loose or leaking. My V*lv* did that. Thought it was a little end gone. Does it sound like 4 cylinders or one?
Art Pearse

Barney, I'm with Dominic - if you adjust the timing so the car will run with worn points block, the spark occurs after the rotor has passed the high tension terminal. I've just been through this and checked by cutting a hole in the old cap to look with the timing light.
Regards,
Mark
M Wellard

Electronic ignition solves all these issues. Fit and forget from the timing aspect.

Steve
Steve Gyles

Thanks everyone, yes I am already using the pertronix points of which I love so that eliminates that possibility. I think it is the timing because I recall a while back the suggestion to advance it untill the engine stars to react and then back off some. I think I am going to just get a timing light and set it back some. I was also goig to try uping the octane the next time i needed a fill up. Would riding around for a few hundred miles have caused any damage?
WMR Bill

Mark, -- That's way I said specifically, "Always set points before setting timing". It is folly to try to run an engine with too-small points gap (although these engine are quite tolerant of wide variations in tuning).
Barney Gaylord

Barney, my comment was relating to ponts set to correct gap but a worn rubbing block and the timing set correctly afterwards. In my case the block wore away in the space of a few 100km after a long layoff (strange). Even with the correct gap the phase of the points alters.
Regards,
Mark
M Wellard

Mark,

It sounds like the bearings of the distributor are worn.
A shaft with side play will continuously change the point gap and so also the dwell and timing.

Mick
M F Anderson

Well the first thing that went through my mind when I read the initial posting was 'big-end bearings', sorry, but it has to be mentioned. How's your oil pressure WMR?
Lindsay Sampford

Bearing were replaced during the rebuild and the oil pressure is excellent at 70 lb start and 20 lb at hot that raises 10 lb for every 1000 rpm it revs. I never did do anything with the distributor so I will be checking that. I am also going to splurge on a can of the "BG44 K" additive. It seems that product gets raving reviews from people in other forums that have used it. Hope to make all these adjustments this weekend.
Thanks for everybody input. One last question not answered, could I have damaged or weakened the valves or piston by running for a while with the advance to far forward?
WMR Bill

This thread was discussed between 19/11/2012 and 21/11/2012

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