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Anyone tried to advance timing during launch?

891 views 7 replies 6 participants last post by  540Hotrod 
#1 · (Edited)
Reading some other information on this topic, knowing what the engine likes is there any benefit to advancing the timing on launch only, then retard it at a given time back to total, when it's under a greater load? Has anyone experimented with this?
 
#2 ·
More timing leaving gives better launch (acceleration) if the tires and chassis can handle it.. Usually less timing at full rpm is more horsepower.


I used to take timing out when I got in high gear but haven't bothered in a couple years.
 
#6 ·
Just to be clear---If car liked 36 degrees in high gear or on dyno, I used to set total timing at 38 degrees and pull 2 degrees out when it hit the high gear switch on the shifter. Takes load off motor/bearings with less timing at end of track and usually accelerates A LITTLE BETTER LEAVING. If the tires and chassis can handle it.
 
#3 ·
I take it thi8s particular engine package launches above normal idle RPM's, as in foot to the floor, against the rev limiter. If that is the case, it should already be at top advance, and retard as RPM's are increased, changing with the load changing.

If this engine launches from an idle, like a Top Fueler, the timing is already fully locked out, and at the detonation point, which would not tolerate any further advance @ launch.

I started a timing topic last year, and promptly got so busy with my engine development work, I didn't get a chance to participate, let alone contribute, but, it all has to do with the time involved to get the burn fully across the top of the piston, making the burn push pressure against the piston top as advantageous as possible, without causing detonation, and/or other burn issues. Some of you have bits and pieces of how this all works right, you all need to get back with it and go forward, so everybody understands, and gets involved with it. One thing to realize is, it takes time, in burning the mixture, to get that full burn across the entire top of the piston, to get the most push to the piston for peak power production.
 
#4 ·
Timing is locked out at 40*. Only pull it for start retard. Where it likes it. Just did some reading and was curious if giving it a little more timing on the hit would lower ET? Would pull it after the launch sometime into the run when it is under a greater load and would be more likely to detonate. Found some interesting reading on the subject and was looking for real world results. More timing at this point seems like a lot...
 
#5 ·
This was an old Junior Stock trick back in the day, (before electronic boxes hit the scene), you would set the timing any where from 2 to approx 6 degrees of advance beyond what the engine liked in high gear. After you launched the car and hit second gear you pulled back on a "choke style cable" attached to the points plate and pulled the plate back retarding the the advance back to where it would pull the top end of second gear and high gear. Every one set them up a little differently based upon gearing, car weight, carburetion, etc., and what worked best for them. Today you can have all this done electronically...look at a MSD, Summit or Jegs catalog...all the toys are there to do it.
 
#8 ·
OK...real real old stuff....

My old tunnel rammed 396 4 speed combo with 5.38's in the rear liked a LOT of timing. I cruised around with it where it actually got to 55* (sort of like having a vacuum advance). Made driveabilty great. The car had a dual point distributor and I copied the old Grumpy Jenkins trick of running the second set of points through a toggle switch beside the shifter. Flip the switch, increase the dwell and decrease the timing. I played with it until it would settle at 40* after tossing the switch. Usually did it in 3rd gear. The engine would change sound and pull hard as heck. Never back to back tested it with 40* locked...but I know it was sure crisp with the 55* in it through the first two gears.


JIM
 
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