Posted By: cornet684me
VACUUM ADVANCE - 11/08/10 04:33 AM
okay, please school me on the use of the vacuum advance on a elec. ignition dist., i am currently running a ready to run elec. dist. with a vacuum advance, i had to disconnect the vacuum advance due to a clearence issue with the dist., i have a slight blog , i have taken the vacuum advance off the dist., i had called the tech at skip white perf., he says that i can weld up the bracket so that the rod coming from the vacuum advance will hold the plate and i can cut the actual vacuum advance canister off the dist., what am i missing by doing this ?
this is a mild 1973 motor home 440/727, comp 268/454 cam, holley 750 vac. secondary, 3.55 sure grip in a 1968 dodge coronet
You'll just lose some MPGs if you do much cruising. Vac Advance is typically only used under light load, high vacuum situations to increase the timing, and squeeze a little more efficiency out.
If you don't care about that, weld the arm and cut it off
Posted By: RapidRobert
Re: VACUUM ADVANCE - 11/08/10 09:58 PM
I'm with Ehrenberg, use it not only for the mileage gain but it'll keep your plugs cleaner. It's the last system you tune on a dist (after initial/total/springs) If you do pin it drill a small hole vertical thru the 2 plates & pin them w a mini bolt/nut w a spacer between the plates so they dont crush/tilt & b 4 you do that you can alter your rotor phasing (if needed) by idling it & w a 1/2" hole drilled in the flat of the dist cap halfway between the center terminal & #1 terminal, freeze the rotor tip like a strobe light on a dance floor and see if it is dead under the terminal (or close to it) or off to one side and depending on which side it is on (& the direction of rotation, you said BB right so CCW) you can shift it opposite the direction of rotation by activating the vac can with a vac pump until the phasing shifts closer & note the vac required then dissassemble the dist & pump in that amt of vac then drill the vertical hole to pin it at that location but note that the vac adv will shift the phasing & w it(the top plate w the magnet) being on an eccentric it will change the reluctor to magnet clearance so check that at the same time (.006-8) at the tightest vane (some vanes stick out a bit more than others). Have the dist loose & tighten the screw on the magnet base then turn the housing in a circle checking each rotor vane & find the tightest one & gap that one then turn the housing till the rotor is under #1 plug wire
Posted By: DaytonaTurbo
Re: VACUUM ADVANCE - 11/10/10 03:18 AM
Plus if it's a 73 440 with original smogger pistons, you should use the vacuum advance to throw in as much timing as you can.
Posted By: 74Cuda
Re: VACUUM ADVANCE - 11/10/10 07:19 AM
The first thing I did was I take the distributor on my 440 Cuda apart and welded about .050 on the inside of the advance slots then changed the springs for full advance at 2800.
This will let me set the total advance at 34 degrees and have 16 degrea at idle. This got rid of my low end bog off the line.
Then set the vacuum pod up for 55 degrees of total advance at 55 mph. The plugs lasted longer, I got better mileage and the car ran a lot better.
Posted By: wireweld
Re: VACUUM ADVANCE - 11/10/10 01:34 PM
How do you set the vacuum pod to get 55 degrees?
Remember that the number stamped on the canister arm is distributor degrees, double that to get crankshaft degrees. Most OEM Mopars were right in the 50-55 deg. total area.
Rick
After 100,000 miles, that'd probably make a difference in the shape of the bore, compared to 100k with EFI.