Crank pulley and timing

[Peter Pleitner]

Hi Whitworth Heads, As promised, I looked for and finally found my spare XPAG crank pulley. Its OD measures 3.75 inch, that is the diameter measured from the very tip or top of the v-belt groove. Contrary to the illustration in the "Brown Book" or owners manual, there is no hole signifying TDC, rather a rectangular groove, encompassing about 3 degrees of crank rotation. I had a transparent degree wheel handy with many concentric circles to ease the centering of the pulley. Consequently I was easily able to measure that a cord which is 8 mm or 5/16 of an inch long represents 10 degrees on the pulley. Interlude in garage: Well, I went back and measured the diameter using a metric scale and arrived at the dimension of between 94 and 95 mm (one side of v-groove seems to not exactly match the other. Multiplying by Pie and dividing by 36 equates to 8.2 and 8.3 mm for ten degrees. I presume that any of these are close enough for us. All of this was precipitated by my TC's sub-par performance at speed (not cold starting), removal of pitted points and replacing them with a Pertronics Ignitor unit acquired from Skip Kelsey at Shadetree Motors last year, the ignition timing data on page 149 of Mike Sherrell's great book, "TCs Forever" , and the article Back to Basics #8, authored by Chip Old for the New England MGT Register, reprinted in their "The T Series Handbook". Hope this doesn't bore too many of you. My interest remains obtaining good data for the advance curve that ought to be produced by the distributor's advance mechanism. Years ago I obtained replacement springs for my distributor. They were both the same and wrong! So I used my old ones. I fear this may be a problem with other dizzys in operation. By the way, my TC's performance is back to normal, starts instantly and pulls strong, having provisionally timed it at idle using a strobe light a little advanced of TDC. With this knowledge I will now be able to determine exactly how much initial advance I have and with the degrees of advance dial-in feature of my strobe light I hope to proof the dynamic function of my distributor's advance mechanism, once we generate the data on this LIST. Cheers, Peter