Wen doing a lean burn elimination could I use light springs in the dizzy for centrifical advance instead of vaccum advance?

I am going to first assume that you are aware that you need a new distributor as the lean burn version has no weights/springs/guts....

Next up, you can use lighter springs but what this actually does is allows the advance to come on sooner and if too light max out your advance quicker...this may not in fact help a street car too well (but works great at the drag strip where you are all or nothing on the throttle). If the springs are too light the weight pegs can bounce off the ends of the slots and timing will 'flutter' badly until rpms are kept constant over a length of time.

The other bad thing is slant six distributors only offer governor slots long enough to allow 30 degrees of mechanical advance, which is pretty long to begin with (I would suppose someone might have fun swapping a small or big block 17L governor into the body to give 34 degrees, but it's not necessary or useful). That being said, the purpose of vacuum advance is to allow more timing when the engine is under a certain load, one of the best gauges for this is a vacc. gauge which will show you throttle plate position, and if the engine is working hard, being throttled, or just putting down the road...if you pick the correct vacc. advance and adjust it to fit the parameters of your vehicle then you will be able to have it come "in" when it's needed, and apply less timing (less vacuum) when it's not...

For the most part if a stocker slant car, it works fairly well with a total inital+Mech+vacc. in the 47-52 degree range depending on vehicle weight, driving style and powertrain options. When accelerating you want it to be down lower to prevent pinging in the 25-30 range...once off the go pedal and on flat land it will want to go back to the 47-ish range...

Theoretically if you used a 1974 Distributor...and set it to 16BTDC inital (that's a fair amount)...and you were to lighten up one spring for a fast initial advance then use the long heavy spring to yard in the last 2 degrees at your highway cruise for a total of 46...but this may not work out so well when you suddenly are in the mid range and the initial+mechanical are now more than the engine wants, even accelreating a heavy truck the timing can outstrip the work the engine is under and start rattling away from lack of fuel/too much advance/more load...but would be easier to regulate if you had less initial, a bit more mech advance then use the vacc. advance to regulate that last bit of advance (0-little if passing and a lot more if putting along at 65 mph for best economy).

Technically speaking if you wanted to go for another option and were good at a laptop you can keep the Lean Burn Distributor and use an MSD - programmable box (MSD-6 version came out last year, MSD-7 has been around a awhile), and you can just let the computer do all the timing you want without changing the distributor...of course the box is a bit more expensive than an afternoon of changing springs...


-D.Idiot

Great reply! I was curios because I was trying to avoid changing carbs as my 1945 doesn't have any ported vacuum ports.