Oz Cheek's Holley regulator modification
I have included some side by side pics of my previously boost reference modified regulator for some comparison. It is usually on the left....My comments are in italics GM
"Greg, I will send you a Holley that I have modified for return, I have made several of these and they worked for me. Unmodified on left/Oz's on right
I change the internals of the unit so that I have a stand pipe,which is the return, making contact with the underside of the diaphragm. The stand pipe is a piece of 1/8 brass pipe which I thread into a bushing that has inside and outside threads. You have to put the bushing into a lathe or have a good eye so as to tap inside threads on the back side straight. Drill the bottom of the regulator so that the 1/8 nipple can have room to be inserted. Comparison of drilled and undrilled bodies You will need to pry out the little spring/ball retainer and remove these prior to drilling.
Care must be taken not to remove the threads in the body of the regulator. Install the pipe so that it protrudes up and into the area of the diaphragm by installing the bushing into the bottom of the regulator.It is important that the threads that are on the inside of the bushing are straight because the pipe must contact the metal portion of the diaphragm at 90 degrease and seal. (My fitting for the outlet pipe, in combination with an appropriate piece of steel tubing should do the same job as Oz's bushing/nipple setup and maybe is easier to get "square" to the diaphragm) Once everything is tight, make a mark on the pipe nipple at the height of the surface the cover bolts to then remove the bushing and cut the pipe squarely and remove any burrs, I drill the side of the diaphragm cover and install a short piece of 3/16 brake line and connect it to boost pressure from the hat or some place above the carb. Grind the top of the cover flat and install an O-ring or nylon washer under the nut. Fuel enters on side, passes across to feed the carb, and the return exits through the bottom. When you crank down on the adjusting screw it pushes the spring and diaphragm against the 1/8 return pipe and raises the pressure to what ever base pressure you want. I found I can get down to 4psi with a high out put Bosch fuel injection pump. When the boost comes up, it pushes against the diaphragm closing the return and raises the pressure.I have tried to share this in the past to save folks from having to buy the more expensive regulators, I don't know if they didn't understand or were afraid to try it but have yet to have any feed back. We have one that I built on the dyno here at KB it worked with 20 pounds of boost. The one I had on the Datsun worked without a glich for five years. " Oz
Comment by Greg: I wonder if more flow could be had across
the regulator if some material was removed here.If
you try this, take care not to grind off these stand-offs,
as they probably keep the diaphragm from getting crooked at boost. My version back together.