Mopar Performance DIST with vac advance?

[rustytoolss]

Can some one tell me how to adjust my base timing and total timing . I just got a used mopar performance electronic small block distributor. Also This distributor has an adjustable vacuum advance can. What is the best way to set the adjustable vacuum advance ? Also should the vac hose be connected to manifold vacuum/ or ported on the mopar performance distributor? This will be used on a daily driver/ cruiser 273

 

[rustytoolss]

OK, well maybe someone would know if I should use ported vacuum ...or not.

 

[65 Dartman]

OK, well maybe someone would know if I should use ported vacuum ...or not.

Yes, use ported vacuum off the carb.

 

[Darter6]

I believe you use a 3/32 allen wrench.Inserted thru the can port.I may get this backwards,, clockwise less, counter clockwise more.Usually I drive it first,if it doesn't ping under part throttle(Like pulling a long hill)good.If it does go about 2 turns at a time till it goes away.I think if you do a search you will find more info.

 

[C130 Chief]

So when setting up a distributor, you work from full power backwards, and do the vacuum advance last. It helps if the carb is pretty close, and you'll have to retrim the idle mixture as you go.

1. Disconnect vacuum advance and plug carb ports.
2. Determine total advance required for best WOT performance (advance/retard to lowest ET).
3. Determine initial timing (advance to smoothest idle/highest steady vacuum).
4. Adjust mechanical advance to give this spread. (So, if your car was quickest with 34 degrees total and idles steady around 14 you need 20 crankshaft degrees of mechanical advance. That's 10 in the distributor).
5. Adjust mechanical advance rate for low RPM performance. (Lighter springs will bring the advance in at lower RPM, but too light will cause detonation. Trial and error).
6. Connect vacuum advance to ported vacuum and tune for part throttle and cruise. (Counterclockwise to decrease/delay. You are only concerned about 1/4 throttle detonation here. Start with the screw mid range which is 8 turns or so from full clockwise).

In most cases, you'll want the vacuum advance connected to the ported source, so it's not a factor at idle. But, if you're running a cam with long duration and have a low static compression ratio your engine may like enough initial timing that it will be difficult to start. In this case a better idle can be accomplished with less initial timing and connecting the advance to full manifold vacuum. Your 273 will be fine connected to the ported side.

 

[Mattax]

Thing is the MP distrbutors often come with a lot of mechanical advance. The later ones have a brass shaft and were made by Mallory. On those you can adjust the mechanical advance as well as the springs. They have a weird curve and are only so-so at high rpm IMO (and I'm using one right now). On older Chrysler made MP distributors, reducing the mechanical advance requires welding or brazing up the slots.

For a non-stock engine, work back from the best performance at WOT in top gear. Keep it conservative 'cause too much advance will 'cause ping and that can be destructive.

On a stock engine, start with the stock specs and see if the engine likes the quicker curve that comes with the MP distributors. So in that case set initial, but then check 1500, 2500 and 3000 rpm timing. Then if you find it pinging at you'll have an idea where it's too much.

Whether to use mechanical or ported depends on what the engine likes. This means in gear. In neutral engines like lots of advance but that's misleading because they only need a couple of horsepower to overcome internal friction. If it's a stock setup, start with what the factory used. Manifold vac was commonly used for distributor advance before EGR, but its best to check your specific application.

 

[rustytoolss]

Thanks Guys