Dual Plug Heads

[carguybill]

I see on the for sale section that new dual plug heads are being sold. I was into hot rodding big time in the early 50's and don't recall even hearing of dual plug heads. So, I'd like to know, other than looking really cool is there any real performance function of these heads?

[48 coupe]

Me either. Must have been a California thing. Late 50's for me.I thought I read a lot of hot rod books.

[KiWinUS]

Those heads are made in New Zealand but there were a few different twin plug heads made here in the US . The ones I know of are :- Elco , Eddie Myer & Roof . There are others I am sure . Other than the "Kool" factor I could not comment on performance .
Cheers
Tony

[V8COOPMAN]

Don't forget.......ya need somethin' like this to light 'em all up. DD

[BUBBAS IGNITION]

I have done quite a few dual plug distributors etc ( NASH) . The amazing thing to me is that the plugs in each cylinder fire at the same time...

However if it look ya want . cant be beat !!!

[Deuce Man]

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I don't think the v 16 distributors are what you need for these heads. Straight eight nashes in theearly thirties had dual plugs from the factory, those are the distributors that were used with the dual plug heads. Rich

[keith oh]

Aircraft piston engines all have duel ignition system spark plugs. When switching from duel to single there is always a lowering of RPMs.

[Bill Batson]

Following up on Bubba's comment:

The 65 hp Continental aircraft engines that were used in Piper Cubs and Aeronca Champs etc. had both plugs fire at the same time. The engine could be upgraded to 75 hp by 1) drilling extra oil holes in the rod big ends (as described by the factory), 2) using a smaller propeller to turn higher RPMs (2300), and 3) changing the timing so the left mag fired at 28 degrees BTDC and the right at 32 degrees BTDC.

Not sure why the timing difference was needed at the higher RPMs but it did work well.

[JSeery]

As keith said, if you have ever been around a dual plug engine you can tell the difference between when only one and two plugs are firing. A lot depends on the head design and other factors, but in general, two plugs burn the fuel in a more efficient manner. Does it make a big difference? Need some dyno/track data to answer that.

[BUBBAS IGNITION]

Originally Posted by Deuce Man

I don't think the v 16 distributors are what you need for these heads. Straight eight nashes in theearly thirties had dual plugs from the factory, those are the distributors that were used with the dual plug heads. Rich

Correct i had packard on the brain today it is Nash ,1934 i believe.......

[flatheadmurre]

Higher energy in the spark gives you several advantages.
If you can ignite the mixture faster so the downtravel of the piston hasnt started you have a fixed volume and pressure which makes it easier to optimise combustion.
Higher spark energy can ignite a leaner mixture.
If you cant have enough energy out of one plug...use 2 !
With todays high energy multispark systems a dual plug system seems a bit outdated except for safety backup as in aviation.
Shure looks good though...i have a KONG setup waiting to go into my 36.

[KiWinUS]

Originally Posted by flatheadmurre

Higher energy in the spark gives you several advantages.
If you can ignite the mixture faster so the downtravel of the piston hasnt started you have a fixed volume and pressure which makes it easier to optimise combustion.
Higher spark energy can ignite a leaner mixture.
If you cant have enough energy out of one plug...use 2 !
With todays high energy multispark systems a dual plug system seems a bit outdated except for safety backup as in aviation.
Shure looks good though...i have a KONG setup waiting to go into my 36.

Yep I forgot "KONG" & I used to own a set of Kong .

[Cartravel]

It was not uncommon to have dual plug heads for Model T & A, both flathead and OHV.

[rotorwrench]

Aircraft engines are a whole different breed from auto engines. Redundancy is mandatory so they have to have the dual ignition systems. It's the placement of the plug in the cylinder that makes the difference for magneto drop off checks. If the plug was in the top of the hemispherical head, a single spark plug would deliver enough power to get good performance as in the Chrysler hemi design.

Boat racing was BIG back in the day so most of the dual ignition systems were for boat racing. Some of the manufacturers even made covers for the heads to keep the plugs dry. Roof and several other manufacturers made dual plug heads and most of them were into boat racing too.

[Ronnieroadster]

Originally Posted by flatheadmurre

Higher energy in the spark gives you several advantages.
If you can ignite the mixture faster so the downtravel of the piston hasnt started you have a fixed volume and pressure which makes it easier to optimise combustion.
Higher spark energy can ignite a leaner mixture.
If you cant have enough energy out of one plug...use 2 !
With todays high energy multispark systems a dual plug system seems a bit outdated except for safety backup as in aviation.
Shure looks good though...i have a KONG setup waiting to go into my 36.

Actually the dual plug idea is still alive and well in production cars and trucks. Look at the new generation HEMI engines dual plugs are standard as well as lots of torque and horse power.

[flatheadmurre]

Yep but thats a whole other idee then increasing flame propagation.
That engine is equipped so opposite cylinder banks share coils.
The primary spark is from a coil over the plug while the secondary spark during powerstroke is coming from opposite banks coil.
The idee is to lower hydrocarbons reducing the need for a restricting catalytic converter.
So it gives more power....but its just compensating what enviromental rules messed up...

[Shadetree]

I have seen old fire trucks with dual ignition but not this configuration. Could this be one?