Single Fire or Dual Fire

Got to replace my Crane Hi 4 Dual Fire Ignition. Should I just get another one or switch to a Single Fire? What is the difference?

You are correct Chuck...continue on!!

I knew you knew what you was taking about!!

My dual fire fried. Just wanted some feedback on which might be better for my 93 inch shovel. Know anything about them?

The Crane HI-4 Dual fire fires both plugs instead of just the plug on the firing stroke. This is called "wasted spark" and there has been probably a million words written about it over the years. HD's official position was that single fire did not provide any advantage so wasted spark was fine.... Well, that held true until they switched to single fire on the XL and on the Twinkies.... Then, single fire had numerous advantages.
There were arguments over less vibration, more power, better starts etc, etc. My train of thought has always been that the only true, provable advantage is that when you fire both plugs at the same time, you have two routes to ground. Under compression it is harder for the spark to jump the gap and when you fire both plugs less energy goes to the firing plug. V-Thunder did some extensive testing on this also.

Unless you have a built Shovel I would simply buy a replacement unit as the coil would need changing also. An option would be to get a Dyna or Compufire selectable mode (single or dual fire) module if they are still available. That way you can go single fire by simply adding a single fire coil and rewiring the module for single fire.

BTW, I just saw the 93 inch bit.... I would suggest switching to single fire and use the 8-3001 or 8-3005 coil. I favored the larger 8-3001. This will give you better spark and more control over the curve if you use the 8-2300 multi-spark box with the software.
Are you dual plugged?

Na, not dual plugged, just running standard heads. I didn't know there was such contravercy over single or dual. However, I think I am just gonna go ahead and get a single fire. Been shopping around and found the kit with the plug wires, coil and ignition for only about 60 bucks more that just a dual fire ignition alone. Based on what I have found out, I probably won't notice a difference between the two. I know it won't smooth out the vibration any, once you stroke the engine, the only way to get a smoother ride is to put it on a truck or trailer. Thanks for your help!

Thanks for the info. Yea, I think I will get the Crane single fire. Had the Crane dual fire before it went south. Maybe I will be able to get less vibration, maybe not. Some say yes, and some say I will never tell the difference. We'll see.

Single-fire is better in my experience, as it does tend to make the engine start quicker, idle smoother & run better @ lower rpms. But you probably won't notice the difference from about 3000 rpm on up & you will not see any HP or torque difference on the dyno. We're dealing with an "odd-fire" engine (firing order = 315-405) & a single-fire ignition only fires the spark-plug for each cylinder @ a specific time. Dual-fire is more complicated (although easier & cheaper to make) & you get the "wasted spark" which can ignite unburned fuel in the exhaust pipes. And the spark-plugs have to work backwards every other time.

In other words, with a dual-fire system, when the high voltage goes down the front plug wire, thru the plug & jumps the gap to ground, it also jumps from the ground on the plug in the rear cylinder back up. Then the rear cylinder's plug fires & it's just the opposite - power goes down thru the plug & the front plug fires backwards - a spark jumping the gap from the ground electrode up to the main electrode in the plug. With stock or relatively mild cams that's no big deal, but the "wasted spark" can be a problem with a lot of overlap in the cams & especially if the engine is running too rich. IMO, single-fire makes the engine easier to tune.