Mechanical fuel pressure gauge question

[ST]

I'm using Autometer gauges and the fuel pressure gauge is mechanical. I've also got a new Holley fuel pump that replaces the stock Ford pump on the s/o. (Holley claims 6 to 7 lbs. for that pump)
When I first start it up the gauge reads between 6 and 61/2lbs. fuel pressure and after driving a short distance it increases to between 9 and 12lbs. If you let off the gas it starts to return to about 7lbs. or so.
I did try switching gauges but I got the same readings. Does 9 to 12lbs. seem like too much or is that normal? I always thought you might blow the needle and seats with that much pressure.
BTW I am using an isolator and don't have a regulator but if the pump is only good for 7lbs. how can it increase?
Thanks!

[427 S/O]

The regulator goes hand in hand with the pump, get the regulator. That should solve your problem, if not you might need a new pump or isolator. Mine stays at a constant 7lbs. feeding 2x4

[Bud Man]

Running a Holley Pump rated at 97 gph, registers a steady 7 psi. On that particular pump, shouldn't need a reg.

For insurance I am also running the mech pump.

Bud

[ST]

I'm only using the mechanical pump also, the electric ones are only turned on when I need the reserve.
Why is that gauge going whacky?

[Michael C Henry]

some times when you put pumps in series you add pressures.7 PSI is a little high for needle and seat. Varring pressure will afect fuel level in bowls. A pressure regulater will limit pressure not make pressure. If pump isn't going to make up for it. as long as the previous pump is supplying addaquet pressure and flow a regulater will keep pressure where set. Now for the bad news a dead ended regulater will shorten pump life. It happened to my dad ,it happened to me. Dead end pump systems do not last for ever.Think out your system before you buy. Used parts are door stops.I'm trying the BG self regulating bypass fuelolg.That and a hand full of parts is over $900, the log is only $220 at summit.