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MG TD TF 1500 - 51 MG TD back firing

Working on a friends car a 1951 MG TD

Her Husband passed away and car sat for almost two years, car would not start changed out the gas & replaced, cap, wires ,condenser ,plugs, replaced seals on both carbs , was back firing thru carb’s before the seals were replaced , adjusted linkage , and checked the vacuum intake on carbs, timing is dead on at 3000, but still have the back firing out the carbs, all help would be appreciated

Thank you in advance
Gale Destelhorst

Could you please explain "... timing is dead on at 3000..." ? Would expect to see ".. timing is dead on at TDC.." Bud
Bud Krueger

Backfiring through the carbs is usually indicative of too lean a mixture.
Lew Palmer

Sticky intake valve? Timing is off? Too lean a mixture? 2 years is a long time for fuel to set without getting a little gummy.
PJ Jennings

Try a different condenser.

Tom Lange
MGT Repair
t lange

Depends on when it's back firing
If it's when you are trying to start it maybe you have the plug leads mixed up
If it starts ok and idles but won't take the throttle then yes , it's short of fuel most likely
When exactly does it backfire
On starting
Engine running free
Under acceleration
On the road under load
William Revit

Put original condenser back in the distributor.

Peter
P G Gilvarry

Backfiring through the carbs is usually indicative of a lean mixture.
Lew Palmer

Or plug leads on wrong plugs, ask me how I know.
P G Gilvarry

Is it idling on all four cylinders? Fire it up and feel the exhaust manifold carefully at each port as it starts to warm up. Sometimes I'll use an infrared thermometer.

If original air cleaner is still on, you wouldn't know if it is backfiring out of one carb or both? Likely only one. Removing air cleaner could give insight or just continue on below.

A dry, sticky intake valve is a possibility as mentioned but after just 2 years, it shouldn't be rusty. You haven't said how long it has idled so maybe it'll clear itself with long warm up. We could use more details as requested above.

Sometimes removing plugs can break carbon loose giving low reading on compression test. Could be a touch of carbon/rust on an intake valve & seat leaking combustion into intake.

You might isolate which cylinder is acting up via compression test or examining the plugs.

A bit of running under load could resolve transient leakage.

JIM N

This thread was discussed between 07/07/2019 and 09/07/2019

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