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Has anyone tried to converted type 4 heads into a twin plug heads?

Yup. Raby's done it, so have a few others. Raby's version, specifically, was more for looks than for performance. Several engines for Spyder replicas (the Spyders were twin-plug from the factory) were built with two plugs per cylinder. Both plugs were up on the top side of the head, so any extra combustion benefits were fairly minimal.

I know of at least one other, done by Paul Guard of Guard Transmission. He sent pics to a buddy of mine. Don't know if it ever ran. I think the second plug on those was on the bottom of the chamber, and it required some fiddling with a lot of stuff on the underside of the head. That one might have had some actual power benefits, but again I'm not sure they were ever run. And they may have had other problems...

--DD

I gotta tell you, I saw that twin plug head setup that Jake did, and heard that engine run, it was pretty freakin' cool. Used an Electromotive Direct Fire Ignition with a toothed wheel and a magnetic pickup. The amount of work that went into making that puppy go was pretty amazing.

Took me 6 solid months to build that puppy......

There used to be a shop in Florida that did a true dual plug conversion. The plugs came in from the bottom of the heads. They were running some sort of Nissan truck dizzy cap to trigger it. They told me a few years ago they haven't done it in quite awhile. Still had the jigs though.

The cap is from a Nissan Z22 engine.... its an 8 plug 4 cylinder from the factory...

My direct fire method is much simpler. I tried the Z-22 dizzy and cap.

we are doing another twin plug engine soon, this time it will have plugs on either side of the chamber, and won't be just for looks. Even with the plugs up top it still made more power, and even ran smoother..

I realize your method is much better. This is what was available for a reasonable price in the early 90s I guess. The direct fire method has much better control and you can stagger the times like you should with the Electromotive unit.

Is there any data regarding imporved performance/efficiency between:
Twin Plugs vs multi spark vs multi pronged plugs?
L. McChesney

The rule of thumb that I heard was that with dual-plug ignition, you could run a full point more compression on the same fuel without any problems. And that was the main benefit.

That was quoted specifically for a 911, but I think the general application is pretty similar.

--DD

Dave,
Do you think that would be true with multispark?
L. McChensey

What, you mean like an MSD system? No. The MSD will let you run the mixture a little fatter without fouling the plugs, and it should help out a standard motor a little tiny bit. It might even let you raise the compression a very very small amount on its own... But it is no substitute for a true dual-plug ignition setup. The sparks are still all going into the same place, while most of the benefit from a dual-plug setup is from having two places where the mixture starts burning.

--DD

My new head design will allow for twin plugs. One on either side of the chamber....

It will be getting alot of test work when we actually do it.

turboteener wrote:There used to be a shop in Florida that did a true dual plug conversion. The plugs came in from the bottom of the heads. They were running some sort of Nissan truck dizzy cap to trigger it. They told me a few years ago they haven't done it in quite awhile. Still had the jigs though.

That was Jay at RPM in Daytona, and I have one of those twin plug engines and a friend has one too. Strong and fast.