Moparts Tech Archive

Elec Topics

Mallory built MP distributor advance

When MP asked us to make distributors for them, Larry Sheppard told me it had to look like a stock distributor from the outside and use a stock dimensioned cap, rotor, pickup and wire harness but he said that I could change the advance mechanisms.

I went with an aftermarket adjustable vacuum advance chamber and our Mallory YH mechanical advance. I wanted to build them with the mechanical advance adjusted at about 20 or 22 degrees but Larry insisted on 26 to 28. I feel this is too much for most high performance engines, especially those with a performance cam but Larry insisted on 26 to 28 degrees so you can only run about 8 to 10 degrees initial. I feel that it is better (for performance engines) to adjust the mechanical advance to about 20 to 22 and then run about 14 to 18 degrees initial timing. This gives you good throttle response off idle and leaves you with a total advance of about 34 to 38 degrees.

We supply the distributor with our lightest YH springs which gives you full 28 degrees at about 2400 degrees or 20 degrees at about 1800 rpm.

The vacuum advance is adjusted to add 20 degrees at 10 inches of vacuum (if I remember correctly). This is also too much usually. Use an allen wrench in the nipple of the vacuum chamber to reduce the vacuum advance to about 10 degrees. (turn counter clockwise to reduce)

What I'm talking about are the MP distributors with cast aluminum housings that look and function very much like an OEM electronic distributor. Mallory has been making them for MP for several years now. MP sells them by themselves and combined with orange boxes.

Although not discussed in MP's instructions, the mechanical advance is a Mallory adjustable YH type (same as used in most Mallory distributors). It is fully adjustable from zero (locked out) to 28 degrees. We set them at 28 degrees when we ship them to MP. All you need to adjust (or lock out) the advance is a Torx driver to loosen two button head screws.

RobbMc

Engineer at Mallory Ignition/Erson Cams/Accel Ignition

Tech Index