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MG TD TF 1500 - TD Timing II (the beginners' questions)

I've just moved onto the issues of tuning so I'm following all threads on this with great interest. I didn't want to gatecrash the current thread but I've just a few questions, if I may, (and please make allowances if I make all sorts of beginner's mistakes).

1. I'd originally set the timing (on idle and with an adjustable timing light) to 10 degrees above TDC, following [my interpretation] of an archived thread on the BBS, but I wasn't too happy with that as the engine was running lumpy and sooting-up all the plugs. Was I wrong in my interpretation of the correct setting?

2. I noticed if I advanced the timing even more, the idle speed increased markedly, leveling-out as it reached 30 degrees and it ran smoother. I suspect that's wrong and when I get time at the weekend I'll have another go, following the advice in the current new thread, setting the timing at 3000 rpm.

3. All the plugs had soft soot on them until I advanced the timing, and adjusting the nuts on the carbs didn't seem to make much difference. After advancing to 30 degrees, the plugs cleaned-up

4. Mine's a Jan '53 TD but the PO had put 1/2" threaded plugs in. Yesterday, I measured the threads in the block and found they're much deeper so I put in some longer reach (3/4") plugs. I've not done much motoring at all (maybe 15 miles or less) since doing all this, in case I'd made a complete hash of it all but I've never heard any pinking, even when driven hard in short bursts, but yesterday - for the first time ever, and after changing the plugs for the longer reach ones, the car ran on after a 10 min run.

5. I'm also getting a slight "miss" and that seems to happen no matter what I've done to the timing, carbs and plugs. It's fairly regular (I can feel it on warmed-up idle, if I put my hand to the exhaust pipe). The dizzy, plugs, coil and HT leads are new but I can't discount the possibility that one of these is faulty.

What should I be doing? Am I on the right lines?

As ever, any and all observations/suggestions are gratefully received.

- Tom.

Tom Bennett - 53TD 24232

Tom,

1. Yes, you misread something. Starting point should be approximately 5 degrees BTDC. Once the engine has started you should rotate the distributor to get the fastest idle, then back off a hair. This gets you in the ballpark.

2. Something is wrong if you have to turn it that far to get a good idle. Like you plan to do, try the 3K idle with the variable timing light. That's the easiest and most accurate method (to my way of thinking) to get the timing correct.

3. I'm not sure when you put in the long reach plugs, before or after you found sooted up plugs. By the way, with today's gas it's common for the plugs to soot up at idle even with the timing and carburetors set correctly. The easiest check is to run the car at a good clip, then shut the engine down and coast to a place where you can check the plugs. If they're still sooted up then you can be sure you're probably running too rich.

4. Good catch on the plug reach! You can easily check to see if they're too long by removing them...if too long you'll have soot on the first 1/4" or so of the plug threads, clean after that. If clean all the way to the tip then they're the correct length. Running on can be caused by carbon build-up (too rich) on the piston top as well as the combustion chamber. I wouldn't worry about it until you get the timing sorted.

5. As for the miss...a lot of things can cause a miss but a common one is a leak around the intake/exhaust manifolds or around the throttle plate on the carbs. Move the car outside, start it up and take an UNLIT, but open, propane torch and move it around the carbs/intake manifold. If there is any change in the idle you've found a leak which could be causing your miss.

Good luck with your troubleshooting...I'm sure you'll end up with a ton of suggestions to work your way through before it's over.

Gene
Gene Gillam

Tom, IMHO the best place to start is with your adjustable timing light in your tool drawer. Dig out a simple 12v light bulb and set the intial timing statically at TDC. Yes, use the right type of plug. I'd suggest NGK BP6ES. The intial TDC timing should get the engine running smoothly. Advancing the timing is for you're ready for tweaking to get a bit more out of the engine. Bud
Bud Krueger (TD10855)

Tom - I agree (up to a point with Bud). Do the static timing as detailed in the Workshop Manual, then break out the timing light and see what the advance is at 3000 rpm. According to Jeff Schlemmer of Advanced Distributors (and does a wonderful job of restoring MG distributors), you should be getting around 30° to 32° of advance if the distributor is working as it should. The run on could be caused by too hot of a heat range on the plugs or insufficient ignition advance, requiring a higher setting of the idle. Cheers - Dave
David DuBois

I like Bud's 'back to basics' approach, but would respectfully suggest that you would be better starting at 4mm bfore the notch on the c/s pulley, giving around 5 degrees BTDC, a good static timing starting point.

Good luck Tom,

John
J C Mitchell

This thread was discussed between 11/07/2011 and 12/07/2011

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