Please comment on my speed secret of the day

[jim_howard_pdx]

Yes I have heard of racer Brown, but not the other... Damn I am really getting old.... Have you heard of the Mongoose? Shirley Muldowney? Dandy Don (Garlits), Gas Rhonda? I've left a lot out, but they were big in my time.

The racing parts now are much better, much lighter, and I think they are pretty fairly priced.

By the way, someone read my speed secrets number two, and picked up on something I was hoping SOMEONE whould mention, especially one of the Cobra 4.6 guys.

Here goes....Old Guy with an 87 GT wins a special prize, although this response belongs in the speed secret number one thread.

I was really counting on someone bringing up a 4 valve head. When you look at a new Acura Integra VTec II making 100 horsepower per liter, while getting over 30 miles per gallon, just what is going on? They are not packing in extra fuel or the gas mileage would crash and burn. So what is it?

It is the quench.

If you get a chance to see the heads on a Honda, you would see that the combustion chamber resembles a roof of a home. Instead of rising to a sharp point, they just transition into a smooth 1/2 inch ridge across the top of the chamber. This is the area where the precombustion takes place. Then the flame propogates down the sides of the roof line.

Measure the quench on this head, and you will find .06 to .08 quench across the entire piston. This is engineering dominance. Since the combustion chamber is split into two roof lines, each with proper quench the flame cannot "explode" like in a Ford wedge head. The burn is even and smooth and actually follows the piston downward as it begins the power stroke.

This is one reason why a supercharged Chrysler Hemi can make 2500 horsepower. The domed pistons force the burn cycle to run from the center and burn down as the piston moves down, so the flame chases the piston burning more of the fuel charge.

A 4V piston design is even more efficient. That is why Honda engines run so damn well for their punny displacement.

On my 358 I have a 57 cc wedge (after shaving the head), and I use a TRW forged 9/1 flat top utilizing a 13cc dish. I set this car up this way so I could run pump gas. But my quench area really stinks. Nothing like what I used on my 428 scj, on any of the hemi's I have built, or any of the 383's and 402 Chevy's I have raced. I figure I have close to 3 or 4 tenths of an inch space between the wedge and the dish.

So guys, throw out those flat top pistons, and get to work with the dome pistons and the dye grinder.

If your rule book requires flat tops and .037 minimum deck height, then angle mill your head to the maximum, and add the cc's back on the piston surface in the way of smooth valve reliefs, maintaining the minimum quench amount they are after. There is no need to have a .3 inch wedge if you can do it with a .18 around the plug, and .08 in the wedge, and .037 at the piston edges.

So 4V engines are the way to go, if you can build a dome that is smooth and follows a roof line design AND NOT A HEMI DESIGN. Buy a honda tuners magazine some time that shows the head and piston so you can see what is possible to generate 100 hp per liter. My Mustang would have 580 HP if it had equivalent heads. That would be SOME RIDE!