Re: [Chevelle-list] distributor total-timing question - BB

[Larry Williams]

I am doing the same thing with my BB.  I just installed a new hyd Comp Cams roller and am using a mechanical advance Mallory Unilite.  Comp Cams help line said that 36 -38 deg total was recommended w/ 8 -10 initial for my cam. The cam # is CB 290-R10.  The Mallory is set at 25 deg total advance, and is at 9 deg initial now.  I have ordered a Mallory kit to  change the total setting.  I do not plan to change the springs.  I rebuilt the 750 Edelbrock AFB.  The valves are zero plus 1/2 turn down.  My problem is that it back fires occasionally.  Could it be a vacuum leak.  The cam was installed at zero.  Have new Taylor Wires to install today.   New carb?  I'm at a loss.  Any suggestions?    ----- Original Message ----- From: Dave Studly To: Chevelle-List@Chevelles.Net Sent: Saturday, February 26, 2005 8:34 PM Subject: [Chevelle-list] distributor total-timing question Does anyone have some semi-accurate information regarding the mechanical and/or vacuum advance curves that are typical in a stock points or HEI distributor? (or typical ‘performance’ settings in a re-curved setup?)  I’m trying to come up with a baseline for my EFI conversion.  If this darn weather would warm up, I’d get my butt in the garage and finish it.   From many of the magazine articles I’ve read, they seem to end up around 36-38 degrees of total timing on typical carb setups.  If you’re running, for example, 12 degrees of initial timing, does this mean the mechanical advance is providing 24-26 degrees of additional timing?  I assume there is no vacuum advance at WOT.  For a performance application, should I have it all in by 3000 RPM, or sooner?   As for the vacuum advance, 10 degrees sticks in my mind as the max amount that it will add.   So, if I’m running down the road at 3500 RPM, high vacuum, I could have 12 degrees initial + 24 degrees mechanical + 10 degrees vacuum = 46 degrees total timing?   -Dave