Farmall M Ignition timing for stock class puller

farmallm46

New User
We have a 46 M with 4" firecraters that we use to compete in the antique stock class pulls in our area. I have searched to try and find the answer to my question but cant find what im looking for. Everyone says to time the motor to 22 degrees at wide open throttle with firecraters but what rpm is wot? The timing advance changes with engine rpm does it not so this doesn't make since to me. If I set my tractor stock rpm at 22degrees at 1650rpm and then increase the rpm to 1750 the total timing at wot will no longer be 22degrees. We run our tractor at 10% over stock. Current rpm at wot is 1750 so what should I set the total timing to? I use a timing advance timing light to set timing.
 
your tractor does not run WOT during the pull,so lower timing is needed in a lugging situation,less pull down more timing,more pull down less timing,is how is is supposed to work.Sometimes a newer high tech timing light leads you astray,I trust the old sure fire way of marks on the fly wheel.That way you know what you have.Unless you run cold plugs,and high test fuel,timing is not your friend under heavy lug.
 
(quoted from post at 14:49:31 04/02/16) your tractor does not run WOT during the pull,so lower timing is needed in a lugging situation,less pull down more timing,more pull down less timing,is how is is supposed to work.Sometimes a newer high tech timing light leads you astray,I trust the old sure fire way of marks on the fly wheel.That way you know what you have.Unless you run cold plugs,and high test fuel,timing is not your friend under heavy lug.

Makes sense, so you are saying I should run less timing advance during a hard pull?
 

and I know that you don't run wide open 1750rpms down the track and the rpms drop under a pull. But if you have your total advance set at 22degress at 1750rpm your timing advance at 1200rpm for example under a pull will be 15degrees(for example). And if you have total advance set at 28degrees for example at 1750rpm then the degrees of advance will be 21degrees at 1200rpm will it not?
That's why my question is what should the total timing advance be set at for a given rpm at WOT cause it affects the timing advance (Centrifugal advance) through out the rpm range.
 
your ignition advances on rpm if it had a 450 head the timing would be 25 at wot which is 1600 so set it according to
the manufacturers specs on the head your running if it's stock . if not a dyno or a lot of experience is needed to find
the spot .
 
(quoted from post at 16:58:38 04/02/16) your ignition advances on rpm if it had a 450 head the timing would be 25 at wot which is 1600 so set it according to
the manufacturers specs on the head your running if it's stock . if not a dyno or a lot of experience is needed to find
the spot .

okay this is 25degrees at the crankshaft correct? all my measurements where done from there
 
Most accurate will be to tune it out
hooked to a dyno. Then you can be
accurate at whatever rpm you want
 
A dyno is the best way. If you can't get access to a
dyno, then use the 22 deg number. Run the tractor
up to 1850 or 1900 rpm. Make sure the distributor
has fully advanced to the stops. Set timing at 22
deg BTDC with a timing light. Lock it down. Reset
governor to 1750 rpm.
 

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