Dual plug heads

[oldcoot]

Well here we go guys. Its an 80FXE with dual plug heads. I have not been running the extra two sparks. I'm thinking about it, but at the local shop the word is it won't be worth the expense to use them. i.e. a new coil. I understand the shovels are not the best at burning all the fuel durring compression so dual plugs help. So would I see any benefit running the dual plugs? And would it be wroth the cost of a new coil and wires. If so , any thoughts about the coil set up----two coils or one four poster?
Thanks abunch
OldCoot

[wreckerman]

i have limited experance on duel plugs but from what i have seen
yes you would benifit from haveing them both in better starts smother running and better fuel burn as for coils duel coils would be the way i would go junior or wide might be able to give you a better answer they have used that set up before

[rwpatton]

Oldcoot

IMHO

The advantage of dual verse single plug is starting. Especially if you have a kicker only. It does burn a little cleaner but seat of the pants power increase is minimal to nonexistant at best.

I have always used two coils but I think the 4 poster might be a cleaner install.

Is it worth it? I'd say yes just for the 'cool factor.'

Just be sure and use the proper ohm coils for the ignition you are running.

RW

[junior]

both the guys have ya on the benefits, but here's a bit on why....

the hemi-head design of the shvels requires a domed piston. the placement of the stock sparkplug in relation to the crown of the piston can cause an obstruction in the flame path during the ignition event. using a dual-plug setup simply ensures a more complete burn of the air/fuel charge.

the seat of the pants dyno may not necessarily register a big incrase in ooph, but it will most certainly start better and likely increase your cruising range a bit....

j

[whodatt]

Thanks for the explaination of the technical aspects junior. I have known of and believed in the benifits of dual plugs for some time, but never really understood the workings of it.

If anyone doubts that they work, go down to your local small airport and get someone to start their piston plane for you. Don't worry, everyone who owns a small plane loves to show it to others. Anyway, have him start it up then once it is running, turn off one of the magnitos. You will not only see (on the tach) but hear a noticable dip in the rpm's. Don't worry, this is one of the pre take-off checks, so no one will have a problem showing it to you.

Each mag goes to only one spark plug in each cylinder. So for the same amount of fuel with both mags on you get a higher rpm which equates to a better fuel burn. The benifits of dual plug heads becomes readily apparent when you see this done.

Just my .02 cents.

[Wide]

You cant beat duel plug heads for performance, like they stated above better combustion=better efficiency=happy motor.


Cant add much else :P

[oldcoot]

Thanks guys. I'll try and not think of that airplane thing while I'm running down the highway.
The tanks and tins are at the panters getting flamed. I'll post a pic or two when it's done.
Be good

[Soretailcat]

Old Coot,
Dual plugging the shovel or ironhead is the single best thing you can do to the engine.You just burn more of what you have in the combustion chamber increasing the efficiency. Because the dual plug setup is so much more efficient, I recommend retarding the timing 5 to 7 degrees. On the really low compression engines 7 or 7.5 to 1, you can try and use the stock timing. Most of the ones I dual plug go with compression and therefore the 5 to 7 degree retard. 10 or 12 years ago I would go to the local bike shop on a nice Saturday morning and park my big shovel rigid out front. Shop owner didn't mind....I did his machine work! Many times people would talk to me about dual plugging. I would pull two of the plug wires, one from each cylinder, and kick the beast to life. As it idled, I would plug up one of the wires and the engine would speed up. I would plug up the other wire and the engine would speed up even more showing that all I was doing was burning more of what was coming in the cylinder. I sold more dual plug jobs than I care to think about. Every customer was more than satisfied. There are other tricks to do with the ignition but I digress.

If you go to my album, in the photo gallery, there is a photo of one of my dual plug shovel heads. With my setup, you do not have to use special plug sockets or drop the pushrod tubes to remove the plugs. I also install a steel insert in the new plug hole that eliminates stripping the 3/8" reach plug threads. Any questions drop me a line.
Soretailcat

[phxbike]

I need to know plug gap for dual plug heads. Its a 78 I just picked up with no history. The plugs in it are short reach. Thanks

[vermilla]

Gentlemen,

I have been running dual plug heads since I picked up my bobber last year...For whatever reason the guy who built the bike didn't hook up both plugs (i.e. he didn't put a 4 poster or dual coils on it). I blew the coil about a week ago and I am going to have to replace it. Any suggestion on specific setups that have worked well for any of you?

It is a highly modified (high compression) shovel, in a '56 rigid frame. I know that it has eletronic ignition, but I am not sure what type or brand. I was told (by the guy I bought it from) that the ignition will work running all four plugs, but money issues prevented him from upgrading the coil.

Any suggestions you have will be appreciated.... - AV