I have a Carter 'Street Super' mechanical fuel pump. It advertised as putting out 5.5 to 7.5 PSI and 120GPH. This on a street/strip 470 with a QFT-850PV carb.

Should I run a fuel pressure regulator with this pump? I can see the fuel level thru the sight glass, and it stays at the bottom of the sight at idle, which is where I put it. If the pump was putting out too much pressure for the carb, wouldn't the fuel level in the bowl climb? Also can too much pressure affect the AFR if the fuel level stays in the right point? Since the bowl is vented, it seems too much pressure couldn't do any harm unless it was able to overfill the fuel bowl.

I recently had the car on a chassis dyno, and it was pig rich at low rpm (AFR=11.5) and some load (2000RPM and 12" of vacuum, it idles around 13", and pulls about 17" at 2000RPM and light load), but the AFR did funny things under WOT. It starts in the high 11.x/low 12.x then goes leaner than 12.8 (up to about 13.5) as it approached peak torque (4200-4400) and then started dropping back towards 12.8 beyond peak torque. I wasn't able to do a full pull on the dyno due to some equipment problems the dyno shop was having and don't know what happens past about 4700.

I don't have a fuel pressure gauge on the car yet, and will be adding one. I'm wondering whether I should add a regulator while I'm at it. It seems there may be some sort of fuel delivery problem, and I agree I need to check the FP to rule that out.

Thanks for your thoughts!

Dave

If your gauge is accurate it should be fine but thats
about the max... anymore and it'll push the needle
off the seat...does it maintain that pressure through
the rpm range... change the jetting to lean it down
EDIT
get some full runs in before you do anything

OK, if I am on the edge with the FP, I guess it is safer to have the regulator on it, so that I don't have to wonder in the future every time I ponder the fuel curve.

I definitely want to get back on the dyno to do some full pulls. I understand your statement about not changing anything until getting a full run. On the other hand, I have some doubts that the fuel pressure is part or sole cause of the fuel curve behavior. I'm not real fast with making jet changes on the fly, and time is money on the dyno.

The low RPM AFR was at steady state, and should have been on the main jets only since the PV is at 4.5. I have been thinking about leaning the primary jets up some, and either going up in the secondaries or the PCVR to compensate for that change before getting the car back to the shop.

Thanks for the response!
Dave