I finally just got around to putting my Firebird back together last weekend. It's been apart on jack stands for the last 1.5 years. During that time the only change I've made to the fuel system was I've switched from a Speed Demon 750 DP to a Pro Systems 950 DP and the AN inlets to the carb bowls since they use different thread sizes. I've noticed in the past my 4309 Mallory (still using the OEM fuel injection pump) will drop some pressure after it gets heat soaked. I normally set the FP with the liquid filled gauge on the fuel rail when cold and I can keep an eye on it after hot from the mechanical Autometer that is mounted in the cowl. The old BG carb would run right around 6-6.5 PSI hot.

Right now it's spiking 8.0 to 8.5 psi. Which seems about 1 PSI higher than before. Should I be worried about it pushing past the needles and seats?

That's at idle just sitting there in the garage with the lopey 800-1000 RPM surge while cold. My narrowband O2 is showing within Stoich range but on the high side. I haven't set anything on the carb yet (idle mixtures, floats, or jets).

 

pull the sight plugs and see or put ones you can see through. i dont know why they dont put clear ones on everything

 

Most carbs like 6.5psi or less...any more than 7 and you risk flooding everything out. I've never worked with DEMON or pro-system, but I can't believe they'd be that different.

 

Too much pressure will cause you to tighten down the needle and seat adjustment too far, causing the bowls to be very low and will result in running out of fuel at wide open throttle.