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Originally Posted by Terry, NJ
Dual spark plugs are fine. How do they mount the dual distributors/magnetos? Do they use a special cam shaft with dual gears? Dual mags on an engine can pick up the speed of the engine about 50 RPM. I'd really like to see one!
Terry
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I have owned 3 dual plug Model-A/B heads, and most of them use(d) a magneto on a side-drive (powered off the outboard side of the timing gear), and a magneto in the cylinder head in lieu of the regular Ford distributor. I had one set-up that used a Early V-8 Distributor that was mounted onto a Model-B distributor in the normal position. Since the early Ford V-8 distributers were basically two 4 cylinder distributers inside of one housing, it worked fairly well. Nissan dual plug distributors (-with leading & trailing firing) have been converted for use on Model-A/B dual plug applications however I don't have any experience with those. As Jim said above, some have used the Stutz distributer, but those things are REAL expensive when you can find them for sale!!
Typically, with the brass-era and A/B engines with dual ignition that I have worked on, the initial timing (BTDC) is set much closer to TDC since you don't need as much lead in the timing to account for flame travel when you have two separate spark plugs lighting the mixture. When only one plug lights the mixture, it typically has only part of that entire mixture that gets lit by the time the piston reaches TDC, so you lose some of the combustion efficiency in that situation. Therefore when all of the fuel & air gets lit, the efficiency is increased which results in a little more RPM increase.
Quote:
Originally Posted by deuce lover
Here is the ad my friend found. The head has compression rating of 8 according to the ad.
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Thank you for sharing this. I would never have thought of the gasifier. Very cool!
I will tell you that when you look at the Yapp head pictured above which supposedly has 6½ compression ratio, and compare it to the Veyet head in the combustion area and in the area over the piston, it appears the Yapp head has a smaller combustion chamber.