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Quote:
Originally Posted by Railcarmover
The key is finding one with good shafts,the upper and lower get galled from lack of lubrication.All model A engines can benefit from mechanical advance,detonation is one of the main causes of bearing failure,the hammer effect of detonation is increased with higher compression
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And advance.
There is a "sweet zone" which is not readily apparent of course.
The range of advance of the Model A distributor is actually GREATER than the Model B.
http://www.fordgarage.com/pages/bdistributoradvance.htm
Quote:
Conclusions:
The measurements above show that the initial static Model B ignition timing point of 19 crankshaft degrees BTDC plus a maximum mechanical centrifugal advance of 17 degrees equals a theoretical geometric maximum total advance of 36 crankshaft degrees. The slots in the centrifugal flyweights limit this travel.
Compare this to a Model A distributor which has an initial timing point of 0 degrees TDC plus an actual manual maximum advance of 40 crankshaft degrees. The breaker plate arm slot in the bakelite distributor body limits this travel.
The Model A ignition uses a zero crankshaft degree (TDC) initial timing point so that the engine can be easily started by hand crank, however it should never be run under load in this "retarded" position. The advance lever should always be advanced 1/3 to 1/2 travel (13 to 20 crankshaft degrees BTDC) on the steering column quadrant after starting the engine, and should generally not be run more than 3/4 advanced on the column under any normal circumstances.
The Model B is a higher compression (cylinder pressure) engine which uses more initial spark advance, and lower maximum advance compared to a Model A. This is consistent with the operation of the B engine and the need to protect it from the effects of running too far retarded or over-advanced.
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Vince infers that "Full Advance" on the Model A distributor is not required and is detrimental to most efficient engine operation - and recommends against running with the advance lever all the way up. He only generally describes use of Model B additional advance against a high compression head.
Joe K