Well I've searched all over and can't seem to find enough info on my own ... maybe someone can clue me in?

I have a 71 Chevelle 350 that I bought from a dealer a few weeks ago. Not entirely sure the details of the engine besides Road Demon Carb, Performer RPM intake, new valve covers (new valves or heads I don't know), and new exaust. Other than that the rest is stock orignal.

My question is:

Is it normal for the fuel pressure from a mechanical fuel pump to be wildly erratic? Now I know there is discussion of "inconsitent" readings from day to day, hot vs cold, and between gauges, loss of pressure over time etc. But what I'm seeing is different. I just intalled a new Mr. Gasket non liquid filled fuel pressure gauge under the hood and needle bounces like crazy . . . +/- 2 psi from somewhere around 8 psi. Practically unreadable. There is a small length of rubber fuel line from the pump to a steel fuel line (to the Carb). With the engine running I can feel the fuel surging, pulsing, through the hose. How much should my fuel pressure bounce? Is that the way mechanical fuel pumps normally opperate? Do I need a new pump? Should I get a pressure regulator? I've already changed out the inline fuel filter with no improvement.

As far as how it runs, moderately inconsistent. Some hessitation at times, a little stumbling power loss, erratic idle . . .too low or too high.

Thoughts anyone? Thanks!

My f.p. gauges always pulsed with a mech. pump.A Mr. Gasket gauge started doing it very eradicate,there was a tiny screw/plug that had come out of the gauge and I found it in the fuel bowl of the carb.I put the screw back and it operated as it did originally.The same gauge sat steady with electric pumps.Replaced it when it started leaking.

the fuel pump operates in a pulsing fashion, so a gauge that's not heavily damped might/will show this. it operates at half engine speed, so at idle you might see the pulsing.

I have the same setup with the mechanical pump and non-liquid filled gauge. The erratic pulsing is normal for that combination. A liquid filled gauge or electric pump will steady the needle. It's not a problem unless you need a precisely accurate reading. Just look at the highest point that the needle goes to and that is your max fuel pressure.

Mine pulses when idleing also. It smooths out when the RPM's go up. Just watch for the high point when it bounces.

Thanks for the info everyone. That's good to know.