Vacuum advance removal, is it possible?

The following was posted by Rick Ehrneberg of Mopar Action:
Tech Question
bob santarsieri, schaumburg, IL, 71 plymouth road runner 440

I have a msd pro billet distributor and msd 6al box. What would be the best setting for the distributor? Right now it is set at 2 heavy silver springs and silver bushing per the instructions. It starts to advance at 1400 and goes to 5500rpm then levels off. What would you suggest. 440ci, 0.040" overbore, 0.474" purple shaft cam, Hedman headers and 3.23 gears. Just street driven. Thanks for your help.

Bob, assuming sufficient octane vs. C.R., you need a curve something close to this:

Under 1400RPM - no advance - set initial at 15 degrees BTDC
2000 - 10 dergees mech (25 total)
2500 - 20 degrees mech (35 total) - all in.

Plus, at LEAST 15 degrees of vacuum advance under light throttle (50 deg. total, 52-55 better).

If it currently doesn't go to full advance until 5500, you're giving up lots of power.

If it currently has less (or no) vacuum advance), you're giving up LOTS of fuel economy and fouling plugs.

Rick

http://www.moparaction.com/Tech/quest/SLOW_CURVE.html

As a fuels chemist and having worked in the fuels and lubricants areas for 30 years, I can say that Rick is exactly correct. Vacuum advance on any engine is necessary for proper operation under light throttle.

Here are the issues that can help people with problems:

If the distributor is not in a good location, move the oil pump drive gear a notch or two, but the factory position works for most people.

If you have irratic spark timing, get a new distributor. Vacuum advance doesn't impact this.

Always use ported vacuum. Never hook the vacuum line to the manifold or the carb port that has vacuum at idle. This will pull the vacuum unit on instantly and cause too much advance at idle and very low speeds, leading to detonation and poor operation.

Use timing tape to KNOW what you advance looks like, and verify the TDC mark on the ballancer. This is critical in older motors as the ring can rotate on the hub making all marks useless.

Set total timing to 36 degrees for most stock and mildly modified motors. Power tune at the track for optimum MPH (carefully, to avoid detonation). If timing needed for best power approaches 40 degrees, look at the entire system for issues.

I run a 30 year old electronic ignition with a Chrome box and the timing is steady using a timing light (+/- 1 degree). This should be OK for most mild engines. more accuracy requires a high end distributor with roller bearings for movement and shaft alignment.

Good Luck,
Bob