Help me understand ignition timing.

[team39763]

I need to set the timing on my truck.  It's done on my laptop.  I can set a timing curve any way I want.  I'm not using the vacume advance feature due to clearance issues with the the carb(got a defective intake from Edelbrock).  I think I have my timing set to 12 at start up and advancing to 32(max) by 3000rpms.   Some people have told me that I need to try 36-40 max timing.  I noticed a guy running a setup similar to mine and he was running 32* all in by 1000rpms.  What's the difference between his curve and mine?  Will he have less low end torque?(someone said he would).  I'm just trying to understand what I need to do with my timing.  I've been told by a few people that you want total timing to come in ASAP...if that's the case, I can do that.  Does it matter if I take off from idle or stall it 3000 first?

[VileZambonie]

It's called a curve because it's non linear. Many things will determine your ignition timing. One is rpm, as rpm increases so should your spark advance. You can set your total advance around 36° initially and use that as a good starting point. Too much timing will result in preignition which can lead to detonation which will destroy your engine and also cause high tailpipe emissions. Late timing will cause a loss of engine performance and also effect emissions. Depending on combustion chamber design, compression ratio etc you will have to essentially just play with it and see what's right for you. Are you running a distributor? You said vacuum advance feature, do you have an HEI? If so get rid of that! Follow your basic ignition map and tweak it from there. 12° initial and 36° total and try different curves. Results will speak for themselves just pay close attention to your knock sensor signal and the sound of pinging!

[jonkmbll89]

Vile, why don't you like HEI? I am looking to buy a new dis. in future and would like to know your pros and cons on this subject.

[team39763]

I'm running the MSD ignition controller that fires the truck coils(6.0).  It has a MAP sensor that can be used for vacuum advance.  But the sensor would hit my carburetor(even with a spacer).  I wish I had the knock sensors, but I couldn't figure out a way to make them work with a carbed setup.  The MSD setup came with 6 preset chips, but they have a 5500 rev limit and that's not high enough.  Is it better to have all the timing come in very early as in just off idle?  What will that do?