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ekennedy21

Properly timing a 1929 AC

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Does anyone have any info on timing a 29 AC?

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1. Check that the magneto points are set to the right gap (15 thou for a FU4)

2. Set the mag at full advance

3. Set cylinder no 1 (front of truck) to 20 degrees or 3 inches on the flywheel  before top dead centre (check through the upper airduct hand hole, there is a pointer)

4. Unclamp the mag drive so that the mag shaft can be moved independent of the engine and rotate so that the distributor arm is pointing at the sector in the cap that corresponds to the lead running to No1 cylinder

5. Fine adjust the mag so that the points are just opening (you can put a bulb and battery across or use a multimeter) then clamp up the mag drive.

 

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2 questions if you could, Where is the upper air duct hand hole? and how do I unclamp the mag drive?

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also my magneto is a bosch zr4 with an impulse if that matters

 

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 The hand hole/ inspection cover in in the drivers compartment fan cover. Rectangular cover held on with 8 screws.

Interested on how to unclamp the magneto too.

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seems to be running well now, but it is idling substantially higher then before the magneto rebuild. Could his be related to the timing? 

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Possible but also may be a matter of readjusting the low speed jet and idle screw to bring it down. The idle may have been raised to compensate for the wear issues in the magneto when it was a working unit..

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Is that the t screw on the bottom of the carb bowl that sticks out at an angle?

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never mind. Found it. The screw up by the throttle plate.

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On ‎5‎/‎18‎/‎2019 at 7:07 PM, ekennedy21 said:

seems to be running well now, but it is idling substantially higher then before the magneto rebuild. Could his be related to the timing? 

It could be - if you are slightly to far advanced at idle it will run a bit quicker. More likely to be the carb though. As long as you don't get pinking when pulling with the ignition advanced then the spark must be more or less in the right place.

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somebody told be that switching from a zenith updraft carb to a stromburg sf-2 will fix all my problems.

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Posted (edited)
2 hours ago, ekennedy21 said:

somebody told be that switching from a zenith updraft carb to a stromburg sf-2 will fix all my problems.

There a 9 different venturi sizes for the Strumberg SF2/SFM2 they range from 13/16" up to 1 1/16" and some have a Drip Tube set up to prevent gravity siphoning of fuel on shut down. I personally think checking the throttle linkage is allowing the butterfly to lay against the curb idle screw, adjusting the Zenith Lo Speed mixture and fine tuning it overall to work with the modern crap gas would be you best bet. 

My ACs all have different carbs, 3 have Tillotson, 2 have Zenith and 1 has a Strumberg SF1/SFM1 .

Edited by 41chevy

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