OHV build just about wrapped up.

[GeneBob]

John, that is a beautiful engine. Those ports are HUGE. It must just start to run at 4000 RPM. I wish there were overhead cam heads for the masses.

[johnneilson]

Originally Posted by GeneBob

John, that is a beautiful engine. Those ports are HUGE. It must just start to run at 4000 RPM. I wish there were overhead cam heads for the masses.

Yes, I would like a SOHC in one of the coops too.
I have a Gemsa head that was never drilled for the ex tubes and am adapting a cam box on top of it. This is a back burner project so it will be a while.

But, back to the subject, I think the rocker heads available now are the best compromise. OHC drives are not easy nor the most reliable, especially if the motor is an interference design. Rocker design is plenty strong and reliable, I have in Bonneville car currently and spin it over 6500 revs.

J

[GeneBob]

Yeah, I would love to try an OHV head too. I am still working on maximizing my Lion III. This winter I may have it planed down to raise the compression to 7:1. I think about 15 more HP would do it.

[JOHNCL]

John, in my research of pent-roof heads for A/B/C engines I have found the front and back cylinder head bolt locations on the driver (left) side quite a challenge compared to the front and back cylinder head bolt locations on the passenger side. These require doglegged ports that can be more flow disruptive on the d-side. Perhaps this is why the exhaust and intake sides were reversed from usual practice. It is easier to exhaust through a doglegged port than it is to intake naturally aspirated. The blueprints of the so-called stagger-valve Frontenac 4-valves per cylinder head which I obtained from the Leo Goosen Archives man (Gordon Eliot White) show the casting complexities the Chevrolet brothers used to deal with these head bolts c. 1930. Your cylinder head's design may be the cat's meow in dealing with this issue. Hope it works. The pent-roof combustion chamber is where modern engine designers have ended up in their search for best combustion.

[johnneilson]

Originally Posted by JOHNCL

John, in my research of pent-roof heads for A/B/C engines I have found the front and back cylinder head bolt locations on the driver (left) side quite a challenge compared to the front and back cylinder head bolt locations on the passenger side. These require doglegged ports that can be more flow disruptive on the d-side. Perhaps this is why the exhaust and intake sides were reversed from usual practice. It is easier to exhaust through a doglegged port than it is to intake naturally aspirated. The blueprints of the so-called stagger-valve Frontenac 4-valves per cylinder head which I obtained from the Leo Goosen Archives man (Gordon Eliot White) show the casting complexities the Chevrolet brothers used to deal with these head bolts c. 1930. Your cylinder head's design may be the cat's meow in dealing with this issue. Hope it works. The pent-roof combustion chamber is where modern engine designers have ended up in their search for best combustion.

John,
The pent roof design is pretty much a function of the valve arrangement.
The first 4 valve, DOHC design was about 1912. It has been refined in the last 100 years as you would expect. The head bolts on the drivers side don't cause any impact the intake ports, the McGee design was where the tracks go clockwise, thus the ports swapped.
I wish I could take credit for this design, I have just been lucky enough to actually work on one or two of them. The late Bruce Johnson started this and Roy Creel has made 7 or 8 different versions to develop it into a World Record holder in Land Speed.
There has been another design using DOHC and three valves per chamber. I still have not finished the valve area calculations, but the possibility of having two plugs per chamber is interesting.

John