I'm trying to figure that out???
I'm sorry for thread jacking but what's the difference between open and close chambered heads and what are the pros/cons of either?
You can look at this several different ways.
To tell by looking at them, an open chamber head has very small quench areas opposite the spark plug pocket (or a"at the top" as it where). The closed chamber head has a combustion chamber that resembles a bathtub only surrounding the valve area. This gets all muddled up when you look at late vs. early closed chambers, almost like the terminology changed.
Performance wise, by themselves it means almost nothing. It all depends on what piston dome/shape you are contemplating or already have.
I do know that if you use a piston designed for an open chamber head with say a 20 or 30 cc dome and install a closed chamber head, they will likely hit on the edge of the chamber, destroying the motor almost immediately.
Flat top pistons or even dish like what would be found on a force inducted motor becomes more of a compression ratio game.
I like open chamber heads for the simple fact that the design is more dynamically sound as far as scavenging and they tend to keep more heat on the entire surface of the piston (which could also be considered detrimental) reducing hot spots in one area which can stimulate some pretty gnarly detonation.
I really don't think there is a wrong answer as long as the chamber size/shape is taken into consideration with the piston dome size/shape.
The open chamber heads tend to build more power at the higher end and low end torque tends to suffer, but non of our jet boats can use any of that low end torque. Not until you get into the high 4,000 RPM does torque even come into play.
I am trying to find an article written by Gromm Racing in San Jose, I don't think it was on the net. It broke down virtually everything you ever wanted to know about cylinder heads and a lit more... It made my head hurt.
That is really all I can think of right now.
GT
