Midget Diagnosis? Calling all Gurus

[Midgey]

Alright you MG Gurus. My beloved is a 74 Midget with the 1275 engine, and Weber DGV carb. Had a rough running engine, reduced power, intermitant backfiring, occasional gasping, irregular idle speeds, louder than normal sound from engine, etc. Had a tune up at Midas: new plugs, points, rotor, plug wires, etc. Checked timing. Came away still rough, but very pretty plugs and new wires. Then went to more reliable shop, where they scoped engine, replaced distributor, instralled Pertronix ignition. Now runs much smoother, and idle speeds seem more stable. But, power is still not what it used to be, and still have intermitant backfiring. WADAYA THINK I SHOULD TRY NEXT? Think the Carb needs a rebuild? The Weber was on it when I got the car 2 years ago. Could that create the sluggishness? Valve adjustment? The last shop listed a replaced valve cover gasket on the parts sheet, so maybe that indicates that they checked valve adjustment? Rings? No compression test listed in the labor description. You can no doubt tell that I am not a mechanic, so spoon feed me your explanation, if you want to take a shot. Your humble servant, Midgey in Albuquerque. /ubbthreads/images/graemlins/driving.gif

 

[Guest]

Seems to me the next step would be a compression check and valve adjustment. You could have a valve that is going bad (leaking).
Bob

 

[Bugeye58]

Well, I'll give it a shot. I'm not a believer in DGV carbs, so I won't go there, but here are a few things I would look at first.

1. Compression test. All cylinders should be roughly the same, and pressure should be no lower than 115.

2. Valve adjustment. .012" cold

3. Timing. 13 degrees BTDC, 1000 RPM, Vacuum advance disconnected and plugged.

4. Vacuum leaks. Spray WD40 or non flammable brake cleaner around the intake manifold, carb gaskets, throttle shaft. Any change in RPM indicates a leak.

That will give you a starting point. If all the above are OK, check back in, and we'll dig deeper.

Personally, I think you got ripped on the distributor change, but I wasn't there, so maybe I shouldn't say anything. Did you take it back to either of the shops, and tell them you weren't satisfied?
By all means, get a Bentley manual and learn how to do this stuff yourself. It is much cheaper, and far more satisfying.
Jeff

 

[NutmegCT]

Well, here's my two cents worth ... my own 76B with 18V engine (Weber DGAV carb) started backfiring and seemed to have lost some of its 64 horses. I tried re-setting the mixture and found it had been set up way too rich. Leaned it to specs and both the problems stopped.

Tom

 

[Midgey]

Thanks to all for the useful comments. I will give these ideas a shot. /ubbthreads/images/graemlins/cheers.gif