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MG TD TF 1500 - Timeing XPAG's

I read somewhere on this B/B that the TD can be timed by starting the car and rotating the distributer clockwise until the engin starts to sputter and backing off a little. Is this a valid methode?

Second question, why does my fresh oil turn black within 500 miles?

Thank for all answers, Tom
Thomas McNamara

Thomas - Timing the XPAG (or any other engine is a bit more complicated than you have been given to understand, though not much. One has to use a tach and a vacuum gaugein conjunction with turning the distributor. The idle is set at 1000 RPM and kept there throughout the procedure by stopping and readjusting it. The vacuum gauge is hooked up to monitor manafold vacuum (I drilled a hole through one of the top carburator mounting bolts and installing a vacuum fitting into it, then replace the normal bolt with the special one whenever I want to set timing). The distributor is then rotated in the clockwise diredtion to advance the timing while monitoring the vacuum gauge and the tach. The trick is to advance the timing for maximum vacuum while keeping the idle at 1000 RPM. Once this peak vacuum is reached, the distributor is then backed off anticlockwise sufficient to drop the vacuum reading by .5" Hg. At this point, the distributor is locked down and left in that spot. I have found this method of timing engines to be quite good and use it on all of my vehicles, since it doesn't require removing vacuum from vacuum advances, or any other special set up other than setting the idle at 1000 RPM.

As to why your fresh oil turns black within 500 miles - this just shows that the dispersants in your oil are doing their job, that is to keep all the combustion by products that find their way into the oil along with other contaminants in the oil suspended where they will be removed by the filter and/or eventially flushed out when you change oil. This is normal on all engines and doesn't indicate excessive wear or any other problems. Large fleet operations use this to their advantage by sending the oil from their vehicles in for analysis before changing the oil, thereby safely streatching the oil change interval. The analysis will also indicate anything abnormal in the engine, such as accelerated wear of the rings, bearings, etc..

Cheers,
Dave

David DuBois

I am sure the method explained by David is the correct one, however I satisfy myself by using a stroboscopic light and adjusting the distributor so that the spark occurs a few degrees before TDC - the manual says at 0 TDC, but we have better fuels since those times - I use 98 unleaded.

Actually I do this on the road because I found it convenient to have a remote on the dashboard, if you want to see details look at

http://vigna.cimsi.cim.ch/~dbaggi/advance

Denis
Denis L. Baggi

Denis - The timing method that I printed above sets the timing at the correct advance for any engine pecularities and the fuel that is being used and it does it without having to guess how far around the crankshaft pully is how many degrees. Further, one does not have to worry about how much advance is being supplied by the centrifical weights. Try it some time and then check it with your timing light, I think you will be supprised at the results. Cheers - Dave
David DuBois

Hey, thanks for all of the information and detail on my timing question. As it stands now, I'm sending the carbs out on the week of 19 June. When they return, if my problem is solved, ( sooty exhaust ), I'll try one of those fixed. What a great bunch of people in the MG-T* hobby.

Tom
Tom McNamara

David, as I said I am sure your method is correct, but for the sake of experimenting - after all, that;s what our cars were meant for - I prefer to adjust timing by ear while I am on the road. Not only does this allow me to take into account the variations of moden fuels, but I also discovered that the optimum advance depends of the temperature of the whole engine. Hence for me the ability of being able to change the advance angle from the dashboard - together of course with the idle, which I copied from the TC by using TC parts - is a lot of fun that makes the driving most pleasurable.

Eventually I'll mount on the dashboard an instrument indicating the spark advance angle, and that will eliminate all guesswork.

Denis
Denis L. Baggi

This thread was discussed between 26/06/2000 and 05/07/2000

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