The Stovebolt Site Forums The Shop Area The HiPo Shop mallory electronic vs vacuum advance distributor

Hey guys, my 235 is running a mallory fully electronic dist. I bought from Patrick's. I love it, trouble free. I'm installing a new 2 barrel carb. ( Holley-Weber 2 stage) from Langdon's. He insists it will only perform to it's full potential with a vacuum advance dist. Patrick's say this mallory has a"tailored advance curve for superior performance thru out rpm range."Who is right? Opinions? Experience?

Vacuum advance is a fuel economy thing. When an engine is running at steady RPM, light throttle, such as level-road highway cruising, the ignition timing can be advanced about 10 degrees or so beyond the "best-power" setting that the centrifugal advance provides for the same RPM range. When even a slight load is applied, such as hill climbing or passing, the vacuum drops off enough to kill the advance, and the engine goes back to making power, not gas mileage. Deliberately running without vacuum advance will cost the average engine 2 or 3 MPG at light-throttle cruise by being unable to advance the timing into the good gas mileage range. OK for racing, lousy for street cruising. For instance, small block V-8's make their best full-throttle power at around 36-37 degrees of advance, while best fuel economy happens at 45-48 degrees with a light, steady throttle setting and minimum load. The vacuum advance provides that extra timing when it's appropriate to have it.
Jerry

Joe, I ran a Mallory Unilite ignition in a VW bug. It failed after about a year and in talking with others I found they had the same experience with Mallory products. Did you consider using a GM HEI ignition?

Inexpensive kits are available to talor the vacuum and centrifugal advance curves of those. I run one in a Chevy 350 powered '32 Ford roadster and it makes good power and exceeds 20 highway MPG.

I'm going to throw in my experience using the Mallory Electronic dizzy from Patricks. One thing that it does like is a bit more base advance that one with a vacuum advance on it. I'm running 15 degrees btdc, rather than the o degree setting of the stock dizzy. Otherwise, it will want to stall at idle speeds, especially coming back to idle from open throttle. Another issue, use of an ignition control box (I'm using a 3LRi myself) improves the performance greatly on these distributors, especially if you're going to use a hotter coil. Seems with the hot coil run through a ballast as shown in the directions cuts the voltage too low to get a solid spark. The box eliminates the ballast, and controls primary voltage based on engine rpm. This setup is working very well for me.
The only issues I've had with my Mallory, other than tinkering with the timing to get it to run smooth at idle, was that the center contact in the cap self destructed. Not sure what happened there, but I haven't had any problems since the new cap was installed.

Intersting. So I stil won't get the improved milage I'm after with the 2 bartrel. I've been running the Mallory formore than3 years with no problems. Very smooth idle and good throttle response. I did use a hot lead from the battery and not from the starter as the old dist. was set up. Patrick's told that would increase it's life span, as the starter increase the volage and can ruin the electronics in the dist. Anyway, it's crazy that a technology as old as vacuum advance cannot be improved on by modern electronics.Next I'll have to remove the electric wiper motors as it decreases the endless variety of wiper speeds that the vacuum gives.I'm not ready to give upn the Mallory. It's trouble free, set at the factory timing, or close to it, it runs great hardly needs the choke at all,& is maintenence free.

Of courde not needing much choke when cold if probably the old rochester B running too rich.. I'm getting the holley weber from Langdon's next week so I'll see how it runs with a more modern progressive 2 barrel. Didn't buy the electric choke with it wanted to see the carb first and see if it could be run with a manual choke. Hopefully this will be an improvement in performance and mileage.