since my advance/retard lever is set at top dead center (TDC) with the lever at top most position, is it right to assume the model T never should fire after top dead center(ATDC)? The total range of the retard lever is always Before top dead center (BTDC)???? I do run a distributor. Bob
Usually the timing is set so that fully up on the steering column lever corresponds to slightly after TDC on #1 cylinder (like about 15 degrees ATDC). This helps prevent kick-back on starting.
When set in this manner, the timing will pass through TDC as the timing lever is pulled down a few notches, then the remaining lever travel will progressively advance the timing more and more before TDC.
Whether you use a distributor or coils, the spark should come after top dead center with the lever all the way up. That will prevent kick back when starting. The kick could break an arm if you crank start the car, or it could break the starter if you use a starter.
I think the word advance confused me. It seems strange to say we are advancing the spark when we are moving away from TDC on the up stroke. Thanks for the help guys. Great forum. Bob
Think of the top position of the spark lever as "retarded" Then the down position will be "advanced". As the engine speeds up, it needs to be advanced more, because it takes a few split seconds for the fuel to ignite. When it is not moving or moving very slowly while cranking, you want the power to come on the downstroke of the piston. If it comes before the piston reaches top, it will start to run backwards (kick). As soon as it starts, the momentum of the engine will carry it over top before the full power is supplied so it can be advanced. So retarded is a spark coming later and advanced the spark comes sooner.
Thanks again Norm. Have you ever considered teaching old people as a profession? Have a great day, Bob
I don't know how old you are Bob, but I am pretty old myself! I have been working with old Fords for over 60 years.