I have often wondered but never ask.
I ask because I know on old fire trucks it was not uncommon for them to have dual ignition setups being they were for emergency and fire use and needed to be reliable.
Some overhead valve set-ups have dual plug holes. Others, I'm not aware of...
Sherman offered a "twin-spark" flat head.
Jay has an ad in the classifieds looking for one, with a picture for reference.
Looks like it was made by Riley?
I'm such a dummy.... I posted a forum question in Jay's classified ad.
Would you actually want to fire two plugs simultaneously? My uninformed thought was that one set would be primary and the other backup.
I'm firing all 8 in my BB RAJO - ZOOM - ZOOM !!!
And no, it's not a redundant system as in an aeroplane.
Wow, so that answers my question.Thanks!
I think for some purposes like a fire truck pumping at a fire if there was a problem with 1 system you would switch over to the other mid crisis and perhaps not be out of service very long.
In my opinion dual plugs offer a very limited redundancy with only one commutator and one set of coils. To make it a truly redundant backup system you'd need two complete ignition systems that each operate independent of the other. Interesting to consider.
Tell us about the power advantages of a dual plug system. Is there a noticeable increase in power? What about carburation, any enhancements to take better advantage of the additional spark?
I had a Nissan truck that was a 4 cylinder with dual plugs it was a 1985. If it was a good concept my 96 Nissan 4 cylinder truck would have the same.
A friend, now deceased, had a dual ignition BB head on his speedster which were independent. I think both fired at or very near the same time. You could hear an RPM drop if either of the systems was shut off but he normally ran with both systems active.
You knew the car Steve, did Ron have two mags or two early distributors on his red #5 car?
Ron was running a Stutz dual distributor set up, Walt.
Henry - yes there is a definite increase in power & rpm - going down the road at a "good clip", if I flip off my exhaust side plugs (intake side has the fuel pump hooked to it with an "upset switch", you can quite noticeably feel the reduction in rpm & speed - wish I could do a short video to demonstrate the rpm drop - pretty cool !
I'm running a (was) NOS Winfield SR downdraft - plenty of gas !
Oh yes, I am running dual ignition switches & MSD Blaster ignition coils.
Some RR engines had twin plugs and two separate ignition systems, coil & mag.
My DHOC barn fresh "Riverside Special" race car had 8 spark plugs and a Bosch dual 2 spark magneto. My Fronty single overhead cam sprint car had 8 spark plugs with a Bosch 2 spark magneto. My other Fronty single over had cam sprint car had 4 spark plugs and a single spark Bosch magneto.
Our Sherman Spitfire has eight plugs and the two Joe Gemsa's we sold have eight plugs and our S.R Frontenac has eight plugs and our BBR Rajo has eight plugs.
For you non fly guys, when you run an engine up on the pad before takeoff you check the mags. On a low powered four cylinder engine you can turn 2500 on the left mag and 2500 on the right mag but when you turn both of them on you can turn 2650.
A lot of early cars had dual ignition. I believe the model K Ford came standard with dual ignition, a magneto, and a battery/coil, with separate plugs for each system, or a dual battery/coil system with a VERY impressive coil box. (Rob, am I right?). I also have seen photos of an NRS Ford with an after-market magneto setup and the battery/coil system with eight spark-plugs.
Pierce Arrow (at least as late as 1925) on some of their larger models had dual ignition (I got to work on one many years ago). The 1925 had two distributors with separate coils and plugs, run from a single switch.
The Sherman heads for model Ts (previously mentioned) came in both single and dual ignition versions, but were a '50s/'60s variation high compression head for model T Fords. For whatever it is worth? Vic Sala loved the Sherman heads and ran a modified modern V8 distributor on a couple of his cars. He also ran a number of original era ohv heads.
Both ohv and flat-head heads were made for model Ts during the 1920s offering dual ignition. Probably the most common one then and now is the "B" series Rajo of which only some originally had dual ignition. There were several versions of the "B" Rajo heads. I don't claim to know enough about the variations to quote which ones had the dual ignition. Rajo heads did seem to change quite a bit from model to model over the years. more than one version had dual ignition.
There were others also, but they tend to be rare.
European and English cars also tended to have dual ignition later than USA cars did (there must be a joke in there somewhere?). MOST USA cars dropped the idea by 1915, except for Pierce Arrow, and maybe Stutz.
Drive carefully, and enjoy, W2
Wayne--I have a 1927 Marmon E-75 four passenger speedster that is six cylinder with dual ignition. There are two coils, twelve plugs and one distributor. "and NO, Marmon is not a foreign car"
The McFarlin automobile had three spark plugs per cylinder
R S C, You may need to post photos of your Marmon (although I think I may have seen one of it before on this site??). They are fantastic automobiles! Several friends of mine have model 34 Marmons (mostly '21 or '22). I know two people that have model 34 speedsters. Quite a sight to see both of them together on a tour along with a couple others as well.
I did not know that Marmon had dual ignition that late.
Frank H, I had heard that McFarlan had triple ignition on at least some cars. A friend of mine used to have Jack Dempsey's roadster. Haven't talked to him much for several years. I don't know if he still has it or not. I heard rumors that it was for sale, but he wasn't the kind to sell many of the cars he really liked.
There were quite a lot of wonderful cars in that era. I wish I could afford some of them. But model Ts probably are more fun!
Drive carefully, and enjoy, W2
I should clarify for those not familiar with many of these cars. A Marmon speedster is like a Hudson speedster during the same era (there were also others). "Speedster" is the official factory designation for a slightly lower sided four passenger (narrower body) touring car.
Another friend, in the same club as the two Marmon speedster owners, had a '21 Hudson speedster (he has since passed away). A few times, all three four passenger touring cars together would be a sight appreciated by only a few people in the know. But that club is usually incredible to tour with. I had been on tours with them that had seven Pierce Arrows on one tour. I missed the tour that had five Locomobiles together on one tour. They usually do three tours a year, members only for insurance/legal reasons. But what tours they are!
A couple years ago, another of their tours (I missed) had I think it was five '25 to'27 five passenger Lincoln Berline sedans in attendance (a usually considered to be very rare car). One or more of the Berlines did not go on the entire tour, but a couple other model L Lincolns did for a major model L Lincoln turnout.
Drive carefully, and enjoy, W2