720 G Electronic Ignition

[DeereValley]

We just got a 720 with an electronic ignition and were wanting to know the spark plug gap. Is it the same as the original? Thank you.

 

[John T]

The full correct answer is IT DEPENDS.

1) Ifffffff the elec ignition has the higher current rated switch capable of mating up with one of the higher energy (lower primary winding resistance) higher voltage coils YES I suggest you run a wider plug gap, maybe in the 0.035 to 0.045 or a lil more, for a wider fatter hotter spark of more surface area to better ignite the fuel. THAT YIELDS THE FULL BENEFIT MORE BANG FOR THE BUCK THE ELEC SWITCH HAS TO OFFER

2) Ifffffff youre running a standard stock coil, although an elec switch still has advantages, I wouldnt run too much of a wider then the stock plug gap, perhaps in the 0.030 or a lil more range.

I always recommend if you use an elec switch to get one suitable for use with the high energy high voltage coils, they have a higher switching current rating cuz some of the higher energy coils have a lower resistance and draw more current.

Heres the deal if you just use a stock coil: The elec switch still offers a more positive faster switching so you ought to get a lil more spark energy discharge across the plugs gap due to improved efficiency, and even a stock coil can rise to a sufficent voltage to arc jump current across a somewhat wider then pure stock plug gap. Many indeed run a lil wider then normal gap when using a stock coil and an elec switch. BUTTTTTTTT if you use a high voltage and high energy coil with an elec switch capable of switching ther higher necessary current and run that wider plug gap THATS WHEN YOU GET THE MOST BENEFIT

REGARDLESS of an elec switch or points or a stock or HV coil, the voltage still rises ONLY to a high enough level to arc current across the plugs gap. The plugs firing voltage is a function of the plug gap and the medium (fuel and compression) in which it fires. As compression increases it takes more voltage to fire the same plug gap.

CHECK WITH THE ELEC SWITCH VENDOR and with knowing what switch you have (its current rating) and what coil you have (stock or high energy with less resistance) then the best gap can be determined. The general uninformed lay opinion/answer would be to YES run a wider gap and thats likely true (as I said, even a stock coil can still produce sufficient voltage to fire a higher voltage due to a wider plug gap) buttttttttt to get the true answer you really need to know WHAT SWITCH AND WHAT COIL YOU HAVE.

This all has to do with ENERGY (discharged across the plug gap) which is volts x amps x time......if you widen the gap and increase the firing voltage then EITHER the current and/or spark duration time has to decrease. THERES NO FREE LUNCH. BUTTTTT the advantage of an elec switch and high energy HV coil and a wider plug gap is MORE ENERGY discharged across the gap i.e. a hotter wider fatter current arc across the plug for a longer duration WHICH CAN BETTER INITIATE COMBUSTION

Can you tell Ima believer in elec high energy ignition (as far as its engineering advantages) lol BUTTTTTTTT if originality and/or the Correct Police are a concern STICK WITH STOCK IGNITION they can provide years of dependable reliable service as they did for over fifty years..

best wishes

John T

 

[Mike Aylward]

Deere Valley, in addition to the good information John gave you I will mention that often you will be somewhat limited in how large a gap you can run due to the physical makeup of the plug. Some plugs will only be able to be opened up to about .040" before the side electrode on the plug becomes misaligned with the center electrode. In my tractors with standard sized plugs I run in the neighborhood of .045 but only certain plugs will let you do this. If you use a 14mm adaptor you can run automotive plugs and increase this gap even more. I do this on my pulling tractor and run about .052" on it without problems. Just something to think about. Mike

 

[buickanddeere]

The limiting factor is too wide a plug gap will cause the spark to jump under the cap before jumping the plug gap.
That's why the automotive manufactures went to larger dia dist caps when electronic ignition was introduced.
Non resistor solid wires and non resistor plugs will help.

 

[Anonymous-0]

So what will a hotter spark do? Have YOU ever had a tractor on the dyno before and after? Is the timing more important than the amount of spark?

I have dyno plenty of tractors (JD and others) and have NEVER seen all this BS you always talk about. A good spark is needed. But anything more is just wasted money in my book. Timing is the most important thing. Check each lobe on a distributor tester to make sure you are getting the spark when it is needed. Change the curve to get max horsepower thru the entire RPM range. But for the best horsepower and drivability, I go with a good set of points, a good coil, set the timing on a dyno, and keep the extra money for something that will truly help.
All that book reading and no hands on experience is truly a waste.

 

[wilamayb]

Ryan,

I've tried to call you a few times, but always get a voice mail with no greeting.

Does your number still 3982? If not send me an email with your new digits.