askulte

It's time I learned more about dish shapes. Since I'll be going with custom pistons anyway, I'd like the dish profile to match the combustion chamber *exactly*. Instead of a simple D shape for the dish, the dish will try to closely mirror the combustion chamber.
This should give a much larger quench zone for less detonation. I'm thinking of running pretty tight quench, but don't know if 0.035" is possible at 20 psi. My intuition says that high RPM's would affect rod stretch more than big boost, so if I keep it at 6k, I should be OK (did some quick calcs, and stress isn't much at 6k on the rods with light pistons and pins).

Next is how to shape the dish for the most fluid motion. The new fastburn chambers get a very good swirl going, which again helps speed combustion and kill detonation. Should the dish be more circular for swirl (like the direct injection pistons I saw at SAE this year), or match the combustion chamber? (Intuition is saying more quench is better).

I'd love to learn more about this, but have exhausted my books (David Vizard, John Heywood, and Gordon Blair so far...).

I hope someone has some ideas.

Andris

PS-I'll try to use 6.125" rods if I can get a strong enough ringland...

Jester

Well see here...the way I figure it..as you go higher in rpm's the rods get effectivly longer do to strech. The more boost you run, the more pressure applied downward to the piston, countering the rods tendancy to strech. So all you gotta do it run MORE boost...and you won't have any worries, run as tight a clearance as you want

lol..yeah that works...really

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JSP Motorsports
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[This message has been edited by Jester (edited June 05, 2001).]

IROCKZ4me

More quench area is a definate plus. Tighter piston to deck clearance is definitely a plus too. Your probably pretty close to the limit of minimum deck clearance but you're right, with light pistons & pins + good steel rods and a 6K limit you should be fine. Also a cast crank would have less flex than forged but will be more brittle. The 6K redline would make a cast crank livable if it wasn't for that pesky 20 PSI boost you plan on running.

The closer you can get the combustion space to a perfect sphere with the spark in the center, the better off you are. I would go with matching the shape of the heads chamber to maximize quench, and vary the depth of the dish in relation to the heads chamber to make the final combustion space as spherical as possible.

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Tracy /AKA IROCKZ4me
'86 IROC-Z Camaro
"Cogito ergo zoom"

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• fully balanced
• Edelbrock headers/ceramic coated
• SLP cat-back
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[This message has been edited by IROCKZ4me (edited June 06, 2001).]