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As we all know, Kadrons like fuel pressure in the 1-2 psi range. Finding an afordable regulator that can be adjusted that low is hard, especially as vendors drop out of the marketplace. 

I initially bought a Holley 12-804 regulator since it's spec'ed to adjust from 1 - 4 psi with a maximum input pressure of 7 psi. It is factory set at 2.8 psi, but adjustable, right?

I was never able to get the output below 3 psi and looked around for alternatives (even calling up Lowbudget to see if Al Sims' guys had any advice). Kaddie Shack carries the dial-type regulator that seems to get no love on thesamba (of course neither does the Holley). A flying saucer shaped regulator #16-9704 did appear to get some love but my experience trying to order one suggests that it is being discontinued. 

So, having struck out on the "easy" route, I looked into modifying the Holley. It appears to have worked and here's what I did:

The Holley 12-804 unit (looks suspiciously like the EMPI unit, eh?):


Pressure is adjusted by using an Allen wrench to turn the screw at the top. Turning inwards raises the pressure. Pressure/screw is locked by the 5/8" nut at bottom of the screw. Inside, the screw presses down on a spring inside the round cap and maintains pressure on a rubber gasket mounted round steel plate. The bottom of the plate has a small round peg that goes into the gas inlet and regulates the fuel pressure. The problem is that the coil spring that mates with the top Allen screw is too strong/tall. Even with the Allen screw removed the pressure is too high for Kadrons (at least on my regulator).

What I did: 

1 - Loosen the 5/8" nut at the the bottom of the Allen screw and remove both. Remove the 4 screws holding the round top in place. Remove the conical spring underneath and nip off 1 - 1/2 turns from the BOTTOM where the spring is wide (see pic). This is so the adjusting screw will still have a stable mating surface with the spring. Use pliers to bend the lower coil upwards until the spring will sit flat with the small end roughly in the middle. Below is the piece I nipped off:


2 - For the heck of it, shoot a small squirt of carb/brake cleaner onto the opening where the pin on the bottom of the pressure plate fits (in case any trash or hose debris has taken up residence there). Place the rubber gasket with the pressure plate (pin down!) on top of the regulator, matching up the 4 screw holes.

3 - Place your modified spring, big side down, in the middle of the pressure plate. Place the regulator top piece on top, loosely attach the 4 screws through the rubber gasket holes and into the base. Look through the Allen screw hole and make sure that the peg at the bottom of the Allen screw will match up with the hole in the top of the conical spring. Adjust as needed and screw in Allen screw until it just seats into the spring. Tighten the 4 top screws firmly, but gorilla strength is not needed. The lock washers should be flattened and should hold the screws in place. If you're worried, blue loctite is fine. Spin the locking 5/8" nut down the Allen screw but don't tighten it.

4 - Look things over one last time and then start the engine. Do not measure the fuel pressure with engine engine not running!!! My initial pressure stabilized around .75 psi. Slowly turn the Allen screw in until it reads around 1.75 psi. Then, while holding the Allen screw steady, tighten up the locking 5/8" nut. Again, gorilla strength isn't necessary and a drop of blue loctite may make you happy. Double check the pressure after you've locked down the Allen screw and readjust if needed.

Ok, that's all I've got for now. If I experience any problems with fuel starvation I'll post back to this thread.

Mike Pickett


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