timing uncertainty!again!
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timing uncertainty!again!
thought i had the timing dialed in on my 69 small block until i talked to a holley tech.i timed it at 35 cetrifigal.idle timing came in at 16.with the vacumme advance hooked back up i have 53 total timing.holley tech says thats way too much.total should only be 36- 38.
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Just reread how do you know it goes to 53 degs ? with the vacuum advance, always interested in knowing something new
Last edited by MotorHead; Aug 7, 2012 at 06:18 PM.
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From: Oxford MA-----You just lost the game!!!!
Keep the shiny side up!
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From: At my Bar drinking and wrenching in Lafayette Colorado
Vacuum advance is very misunderstood by most people. For this reason, I have written the "Vacuum Advance" tech paper in cooperation with Duke Williams and John Hinckley - two of the most respected automotive engine engineers in the world. Please drop me an e-mail request for this paper if you need clarification on the vacuum advance principles. Bottom line is this: Your "total timing" is perfect. Your vacuum advance is also perfect, but could be reduced by perhaps 4 degrees, but this is not enough to cause any concern or issues. The "total combined timing" (full centrifugal advance plus the vacuum advance) at 53 degrees is perfect, and should give you actual timing at idle of about 30-some degrees for very good engine operation. With the current burn rate of modern pump gas, we see that this "total combined" timing could be reduced to about 47 degrees, if the car is "jerking" or "trailer hitching" at cruise speed. Otherwise, you got it nailed!
Lars
V8FastCars@msn.com
Last edited by lars; Aug 7, 2012 at 09:30 PM.
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thought i had it right.i am still trying to dial in the carb.getting some sputtering under acceleration and no color on plug readings.i did throw 12 gallons of av gas in on initial start up. i may go up a few jet sizes.
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Well, if your initial timing is 16, and full centrifugal advance is at 35, then all you have to do is plug in the vacuum advance. If the ignition timing goes up to 34 at idle, then 18 of those degrees must be from vacuum advance, right? 35+18=53, and voila!! Easy, peasy, lemon-squeezy!
Keep the shiny side up!
Scott
Keep the shiny side up!
Scott
I didn't know you get the highest manifold vacuum, therefore the highest ( in degs ) vacuum advance at idle, you learn something new every day
