-------------- Original message from Steven Boese <sboese@uwyo.edu>: --------------


> At the Rotorfest, I showed some data concerning fuel pressure
> instability with my Mallory adjustable regulator and the improvement as
> a result of installing the non-adjustable OEM Mazda regulator.
>
> Recently, I noticed that Mallory came out with a rebuild kit (part#
> 3178) for the 4305M/4307M regulator which appeared to be a different
> design rather than simply replacement parts.
>
> Out of curiosity, I ordered the kit to see if the regulator would
> actually regulate with the new parts. The picture labeled "new parts
> bad seat" shows what I received. The teflon seat looked like it had
> been hacked out with a dull serrated knife. I coated the ball with a
> magic marker and placed it on the seat so the points of contact would
> show up black in the picture. There was no way that the parts would
> work as received.
>
> It was simple enough to repair the seat in the lathe and the results are
> shown in the picture labeled "new parts repaired seat".
>
> The picture labeled "old and new parts" show the old parts in the lower
> left and the new parts in the lower right. The old parts had already
> been altered from using a rubber X-ring seal to using a teflon seal with
> much less friction in the bore of the cylinder attached to the
> diaphragm. This had resulted in a decrease in hysteresis from
> over 15 psi to about 5 psi.
>
> When installed on my fuel injector test bench, the old parts as shown
> would exhibit the hysteresis and sometimes the fuel pressure would
> oscillate turning the pressure gauge needle to a blur going from about
> 15 to 60 psi and back very rapidly.
>
> With the repaired new parts installed and using only the large outer
> spring, the fuel pressure was absolutely stable at any pressure I set it
> to. When set at 40 psi, the fuel pressure followed manifold pressure
> changes applied to the sensing port smoothly with no hysteresis. This
> is the result of only a few minutes running on the test bench, but the
> improvement in fuel pressure regulation is very marked. If you have the
> old style parts in a Mallory regulator and the fuel pressure isn't as
> stable as you expect it to be (Bobby?), the repair kit may be something
> to consider (assuming they send you usable parts).
>
> The last picture labeled "assembled regulator" shows the jam nut with a
> gasket between it and another nut with a cap welded on it which
> eliminated the air leak through the threads of the adjustment rod.
>
> For what it is worth...
>
> Steve Boese
>