Now we are getting somewhere. I believe the SOMENDER-SINGH grooves are simply a crutch for sloppy tolerances in engine building. Ideally, the piston should come within .001" from the head at all RPM. That promotes maximum turbulance. Putting grooves in the pistons simply makes it hard for the mixture in the grooves to burn. Running minimum quench requires research with any piston/rod/ring combo to get the pistons as close to the head as possible. That takes the kind of money that most people don't have.
The old Gurney/Westlake engines used an angled flycut on the tops of the pistons in an effort to increase turbulance. Two strokes use a squish band to achieve the same effect.
The lack of turbulance is what makes hemi's the combustion chamber of choice for fuel burners; You don't want to be compressing liquid fuel in a quench area.
The auto makers do have a problem with quench; they need to provide enough area for carbon build-up over time. It is also said to make engines noisier. Who cares about that? That is something most of us hobbiest need not concern ourselves with.
My present 406 is running the piston .005" out of the hole. I wanted .015", but I hated to take another .010" off the top of the block since we had to grind way too much off to use KB pistons.
If you haven't bought a crank yet, I would talk to Wolfplace about using a 3.810" stroke crank with the KB pistons to see if that could eliminate grinding a lot off the deck area. That's what I'm looking at for my next 406/415.
A lot of people don't like the KB pistons. I have one of the first sets they made for the 406, and I haven't had any trouble with them. I'm using them with .0025" clearance. Next time, I'll go .0015" and .010 quench. I'm not saying you should do that, but that's the way I'm leaning toward my next street engine.
Also, check out The Old One's website. http://www.theoldone.com/
Endon has done some interesting head studies, most of which make sense to me. I wish he lived next door. It's all about sucking the maximum amount of heat energy out of what we are burning. There is still room for improvment.
406 SB, Original Bill Thomas '63 Rochester FI
AFR 210, Lunati 501C2LUN, 255/[email protected]
10:1, TH400, 3.31's, 4400 SS
"Life is too short to not run a solid roller cam."
"Nothing is impossible; if you don't know what you're talking about."