Dan, while some of your math is wrong (350 is a 4" bore, 3.48" stroke), your basically on the right track. There is a certain amount of time needed for the flame front to burn all of the air fuel mixture. Also, some might be surprised to learn that higher-octane fuel burns slower (although, I believe, more completely) than lower octane fuel, which is why advancing the timing often goes hand-in-hand with putting in some good gas.
-Dave -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of [EMAIL PROTECTED] Sent: Saturday, June 08, 2002 11:17 PM To: [EMAIL PROTECTED] Subject: Re: [Chevelle-List] Advancing Timing Keith, Just a guess here, but even as low as 1500 RPM, the time it takes for a piston to go from 12 degrees BTDC to TDC has got to be milliseconds. So, if you fire it at say, 6 degrees BTDC, and figure the time it takes for the air/fuel mixture to fully ignite, there's a possibility that the piston may actually be on its way back down the cylinder bore before any power is applied, wasting some of the power stroke. Firing the plug earlier, at 12 degrees BTDC, gives you the time needed to fully ignite the charge while the piston is at or near the very beginning of the power stroke. Lets do the math. 1500 RPM equals 25 revolutions per second. That's 9000 degrees of travel every second. Assuming that a 350 mouse motor is a 4" stroke, ( I'm not sure ), 12 degrees BTDC equals roughly 1/8". That's 10.8 milliseconds before TDC. And that's at a fast idle....imagine 4 or 5 thousand RPMs. OR, I could be way off base with these figures. I never thought about it before, and its the best answer I could come up with quickly. Take it easy, its nice outside. Dan McIntosh 65 Malibu ----------------------------------------------------- To Unsubscribe please visit www.chevelles.net/list.html To start a new topic, send mail to: [EMAIL PROTECTED]
