38 A john Deere Pulling tractor Ignition timing for E-85

[T. Brown]

I am building a 38 A John Deere pulling tractor. I plan on using E-85 fuel. I have a wico C magneto.How do I set the ignition timing advance for E-85 fuel.

 

[Mike M]

The only way to set the timing on something like that is to run it on the dyno with the same fuel you are going to use and set the timing while running for max. HP same thing with setting the carb. set it on the dyno for max. HP
Once you have done it that way you will see on the gauge how much difference a little bit can make.

 

[Anonymous-0]

You are going to have to switch the impulse setting to give you more initial advance they are set at 25 degree lag, then play with the mag advance, like Mike says on a dyno. CHANGING LAG ANGLE sometimes makes hand starting VERY difficult.

 

[John T]

I agree with Mike, an under load Dyno test will tell ya where to set the run time advance timing on that mag. Have it loosened just enought so it can be rotated and forward CW retards it while backwards CCW advances it. Of course, when you rotate the mag in its flange youre gonna be changing the impulse start timing also remember.

If you have real high compression you might wanna consider at least a Wico X Mag or even one of the high energy pulling mags that Roberts n others builds or if it really becomes an issue then Id opt for a battery powered coil ignition and use an electronic switch and high energy high voltage coil.

John T

 

[John T]

Gary, Im NOT sure setting here we can know if he needs more "initial advance", cuz the impulse start timing cant be too much faster then dead TDC otherwise it may kick back when starting. Also, the lag angle setting is determined by whichever drive cup he has, i.e. yes 25 iffffffff he has a 25 degree drive cup but a lot of the older C mags had 35 degree drive cups, which were meant more for low octane fuel/distillate/tractor fuel tractors.

Hope this helps

John T

 

[RobMD]

Sounds like a good time to have fun with a dyno! Tinkering and listening to the engine labor is music to an old-timers ears.