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Re: Piston specs

Subject: Re: Piston specs
Date: Sat, 8 Sep 2001 12:54:14 EDT
In a message dated 9/8/01 8:53:35 AM Pacific Daylight Time, writes:

> I've not cc'd the head, does anyone know the stock specs for these
> values. 

It depends on which head you are using.

> In a related question, what would be the optimum compression ratio to
> run with the intent of supercharging the motor, assuming 90 Octane
> fuel?

8:1.  If you use higher octane, say 92, you can run 8.5, and of course it 
depends on what pressure you will be blowing at - the old Judson 3 psi is a 
heck of a lot different from an 8 psi blower.

 Can someone who has built a motor to be supercharged, or who has
> the ability to calculate this stuff out, give me what specs I'd need
> (i.e. what did/would YOU order?). 
> The values that I suspect that they really want is distance from pin
> to top of piston and how many ccs to dish the piston.

Actually, you may not get ANY dish in the piston. Many manufacturers prefer 
for ease of machining to simply lower the compression height of a flat top 
piston. It works for Chryslers!

Decide on your desired compression ration, then cc your head chamber, add the 
gasket and plug tip volume, and calculate what additional unswept volume must 
be present to get that value, using the swept volume of whatever size engine 
you are using. You'll probably end up with flat top pistons some way down the 
bore when at TDC.


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