Lars, Mike, TT, and others

big2bird

Charter Member, Founder Bird-Run, Cruise-In Bird-R
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Mar 5, 2008
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Anaheim, Ca.
This might turn out to be an interesting discussion.
An old friend from HS is building a very esoteric Model T race engine.
It has a billet counterbalanced crank, a set of custom Carillo billet rods, custom cast pistons, and a Rajo head. This car is built to withstand 8,000 RPM, and even has a NOS block. Money seems to be no object at this time. I'll post some pics when I get the chance.
Now, this particular head has two sets of spark plugs, and he "thinks" he wants to run dual ignition for dual flame fronts.
I have read some about guys doing this,(Dual plugs) but don't see what gain it is. They seem to use retarded timing at lower RPM, with little gain at higher RPM.
1)Would it really do much for HP gain?
2)How could you do this? (Dual pick-up/coils?)
3)Is it just a big PITA? Not really feasable?
4)Tell me whatever I should know to help/discourage him.

I really need to have you guys think this one out, or help me to try it for him.
 
MY first thought is the one coil per cyl, and the 'waste spark' the way they do so many cars today....4 cyl with two coils....so you still get two sparks into one cyl that way....I don't think it matter which a way the spark jump takes place, long as it's times right....

:skeptic::hissyfit::eek:
 
This might turn out to be an interesting discussion.
An old friend from HS is building a very esoteric Model T race engine.
It has a billet counterbalanced crank, a set of custom Carillo billet rods, custom cast pistons, and a Rajo head. This car is built to withstand 8,000 RPM, and even has a NOS block. Money seems to be no object at this time. I'll post some pics when I get the chance.
Now, this particular head has two sets of spark plugs, and he "thinks" he wants to run dual ignition for dual flame fronts.
I have read some about guys doing this,(Dual plugs) but don't see what gain it is. They seem to use retarded timing at lower RPM, with little gain at higher RPM. Well, it's not really retarded timing. As long as you light the stuff off so that the peak pressure point occurs at 15* ATDC, you're at correct timing.
1)Would it really do much for HP gain? A little. Two plugs, at somewhat opposite sides of the cylinder, will reduce the time it takes for the flame front(s) to consume all the fuel. With a reduced combustion time required (to meet that 15*ATDC peak pressure point), you can light the mixture off later than a conventional single plug application. The later you can light off the mixture, the less time the piston is doing negative work by trying to compress a burning mixture prior to TDC. This frees up a few horsepower.
2)How could you do this? (Dual pick-up/coils?) Several ways. The cheapest would probably be a single pickup sensor (of any resolution that the ignition controller needs), along with four dual tower coils. The coil secondaries would have to be wired up in the usual 1-4 and 3-2 fashion to allow waste spark. Eight coils is also doable and fancier looking, but more expensive in both coil count and ignition module complexity.
3)Is it just a big PITA? Not really feasable? It's certainly feasible, but will take some work. After all, there's twice as much stuff to route and connect. But the coolness factor helps compensate for the extra work.
4)Tell me whatever I should know to help/discourage him. There's plenty of knowledge and experience on this site. Whether he has questions or not, I think his project would be of interest to several of us here. Keep us updated
I really need to have you guys think this one out, or help me to try it for him.

It really doesn't seem like that big of a deal. There's essentially double of everything on the high current/high voltage side, but the controller can be quite similar to a normal single plug system. The only down side I can think of at the moment is if there is a plug failure or coil failure while the engine is being driven hard for a long time. Due to the nature of a faster burn with two plugs, if you lose one plug or coil it makes the combustion process for that cylinder (or cylinder pair) think that you are asking it to run retarded timing in that cylinder. This obviously heats up the exhaust valve a bit more than desired. It would seem to be handy to have a manual disable of one system at a time (for diagnostics) to see if there is any dissimilarity in the way the engine runs with one set of four plugs versus the other four plugs. (It will always run soggier in one plug mode versus two plug mode.)
 
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That's encouraging news. I too am curious about it. The Model C? Rajo head was manufactured with dual spark plug bosses directly opposed in the head, across from each other. Of course, early 20's ignition at dual propagation failed, and usually back up magnetos were used.
I will have Mark join, and include some photographs of this project. I am quite curious about how much HP he can get before it grenades. :phone:
He is waiting on a billet alum flywheel right now, and expects completion in the next 6 months or so.
Although not the project he dreamed of in HS, it's quite a deal for sure. THAT engine, which he sold some 10 years ago, was a hemi chambered dual overhead cam Gallivan, which is a very rare dog itself. The oldthymers told us of running 8,000 RPM on alcohol with it back in the day.:crap:
 
8 grand is booking along even for today....that old NASCAR engine guy used to say about 8 grand for the old Pontiac engines he built for them....
and they were long stroke engines as we know....

:stirpot:
 
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