ignition timing... and not "how to"

[creative1]

ok... just installed an FBO ignition system, so i had the timing light out.

now... in another post it was in the 'performance' topic section), i had stated that after taking the truck to the track and playing with the timing, i found that it ran best with 20* initial and 42* total (all in at 3000 rpm). actually, i quit advancing the timing at that point, because i was worried about the amount of advance.

ok... back to the question. i have read several posts that say forget the timing light. use a vacuum gauge and time the engine for best vacuum. just for kicks, i tried this. by advancing the initial timing to 34*, i gained 3" of vacuum. at 36* the engine begins to develope a misfire.

if the vacuum gauge method is a good way to set ignition timing, why does my engine want so much?

now before someone jumps in and says "your damper has slipped" or something, my damper has NOT slipped! it was correct when i installed the camshaft 8 months ago, and the timing HAS NOT CHANGED since then, except what I changed it.

the specs for the cam and basic engine are in my sig. the truck has a 750 speed demon carb and an edelbrock performer 440 intake. it is a smogger motor... 8.1:1 compression AT BEST. most likely more like 7.8:1.

this has me confused... and i want to know WHY.

thanks for any input.

[Don]

The next time that who told you to set your timing by vacuum instead of a good timing light, get out your big phillips screwdriver and stab that stupid SOB and send him back to his shade tree to die a slow and misurable death.

You can use your vacuum gauge to determine where the engine likes the timing at idle but this is a method that should be used by someone who really understands how the curve works and it's not the most vacuum, it's a reasonable point where Vac Vs. Cam duration curve begins to flatten out.

Leave distributor curving to a professional and kep amatures away from your tune-up.

You may think your getting the most power out of your engine at 42* but your building way to much combustion chamber heat and you are risking a melt down.

20 Initial is fine as long as it doesn't kick the nose off the starter, you must get the total limited to about 34-35.

Have look here:

www.4secondsflat.com/Technical_Information_for_Ignition_and_Carburetion.html

read the articles on ignition and tuning

[creative1]

just for everyone's peace of mind, that was one of those trial things... just had to try it to see what happened... you know what i mean?

i am pretty happy with the way the truck runs with the initial set at 13* and the total (init and mech) at 37*. truck is pretty consistant at 15.23-15.30 ET'S. i could win a LOT of races if i could get my reaction time UP to .500 or so... lol... these .430 REDS arent getting the job done! and when i get a chance to run with a .400 pro tree, it is always against someone with something like a 600+ cid engine and a 14-71 blown, alcohol injected motor!

but hey... they can always break something