Re: Big Boys Heads
I have a set of Grancor heads that had a very intersting chamber for a pop up piston. but the plug was in the stock location. I used these heads on the Bovell engine with a 3 3/4 stroke piston on a 4" crank. Unfortunately the dydo wouldn't pick up the load. I shipped the engine to Cal where the truck was, and flew out there. No Truck and a firm disagreement with the owner. Flew home with out it. Never saw it or the money again.
Bummer, At least I have a picture of the chamber, and it does resemble the Harley chambe.
the location of the plug has a lot to do with the flame front. The flathead has a very long flame front and placing the plug at the far end of the chamber allows the pressure in the chamber to denate the fuel charge. using the .050 piston to head clearance removes the vast majority of the AF over to the transfer ares with a high degree of turbulence, which will urn more of the Af mixture. The result is more power from less fuem.
At least that's the theory. Having the plug away from any valves allow the use of a power tip plug. Another plus. If this doesn't improve power, it will sure improve economy.
Gramps
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