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Background: When I got the car, it was a stock L26 with flat top carburetors. Three years ago, I changed out the carburetors for round top carburetors. For a while I noticed that after I had been running at freeway speeds, returning to stop-and-go traffic would result in hesitation during acceleration until it seemed like the car cooled down for a while. I enriched carburetors some more, and the problem seemed to go away. In February, I did an engine swap, putting in an L28 with an N47 Maxima head. Since the head wasn't configured for a mechanical fuel pump, I just ran the stock electric fuel pump. The hesitation returned, even with enriching the carburetors even more. I installed a fuel pressure gauge and found the pressure to be around 2.5 PSI. I changed out to a small Holley fuel pump (12-147), but the pressure dropped down to 2 PSI. Saturday I changed out the fuel pump for a bigger Holley fuel pump with a fuel pressure regulator (L:12-802-1). The FPR was installed downstream of the fuel rail. At first, the pressure was at 12 PSI. I opened the small orifice on the exit of the fuel rail. The pressure dropped to 6 PSI. Moving the adjustment on top of the FPR did not raise or lower the fuel pressure. I moved the FPR to in front of the fuel rail. The pressure held at 4 PSI. I thought I was good to go. Today I drove the car to help a friend with his Z. It did fine on the trip down. It did fine when I took him in a ride in the car. When I was leaving, the old problem returned. I checked the fuel pressure when I got home. It was below 2 PSI. I moved the FPR back to downstream of the fuel rail. Pressure was 2.5 PSI. Again, using the adjustment screw did not change the pressure. I am out of ideas.

Hi folks, I am a new Z owner (1972), and looking forward to refreshing/restoring this beautiful car. She currently runs OK, but could be better. I am, by no means, a great mechanic, but it appears that there are plenty of helpful folks in this forum. One of the previous owners of this car installed a CR PRO/FUEL adjustable pressure regulator downstream of the fuel pump, prior to the carbs. It is set on 4.5 (I assume this means 4.5 psi). I am not sure of the need for this fuel pressure regulator. I have read many complimentary comments on Z-Therapy's work in refurbishing the dual SUs, so I am planning to take that route. If the carbs are rebuilt/balanced, have any of you had the need for such a fuel pressure regulator? Should I be concerned about the fuel pump? I suppose I could easily remove the regulator to see how she runs. Any comments on this aftermarket piece would be appreciated. Thanks, Steve