[Radman]

It may not be the fuel pump's fault. Todays gas with the ethanol added is much less dense than straight gas. You may just need to set the floate in the carburetor about 116 of an inch lower.

[Formulajones]

You have a carb that doesn't survive anything over 5 psi?

Every mechanical I've had and used will always lose psi as it gets hot, not gain psi. If you're having a psi gain problem with heat or after heat soak, it sounds more like a fuel heating issue somewhere causing it to build pressure. Likely not the pump but something elsewhere in the fuel delivery system.

All the airtechs, AC's and Carter's Ive used (which are all the same pump) all vary a little bit with their psi but I've never had one that was over 8psi and never had a carb that wouldn't work with what ever psi I wound up with. Some were lower psi but what I never wanted was psi dropping under load, that's a worse problem to have.

These days I don't buy the store bought pumps like the wannabe AC's or Carter's because they have become too unreliable. The last Carter's I bought, first one died a block from the house and the second one died 4 miles from the house. The third time Napa just said never mind and refunded my money LOL. I depleted their stock that day.
If I need a mechanical pump these days I use either RobbMC or I'll buy a Holley mechanical from summit or something similar. I'm more curious as to why your carb is so sensitive to pressures above 5 psi.

As an example I run a summit brand Holley style mechanical on the nomad. I believe it's the 90 gph version but doesn't require a regulator. On cold start it has 9psi and it runs perfectly fine. After driving a bit and things get warmed up it drops to 7 psi and stays there. I consider this perfectly normal and the car drives and functions as it should.

[gtobird]

Originally Posted by Formulajones

You have a carb that doesn't survive anything over 5 psi?

Every mechanical I've had and used will always lose psi as it gets hot, not gain psi. If you're having a psi gain problem with heat or after heat soak, it sounds more like a fuel heating issue somewhere causing it to build pressure. Likely not the pump but something elsewhere in the fuel delivery system.

All the airtechs, AC's and Carter's Ive used (which are all the same pump) all vary a little bit with their psi but I've never had one that was over 8psi and never had a carb that wouldn't work with what ever psi I wound up with. Some were lower psi but what I never wanted was psi dropping under load, that's a worse problem to have.

These days I don't buy the store bought pumps like the wannabe AC's or Carter's because they have become too unreliable. The last Carter's I bought, first one died a block from the house and the second one died 4 miles from the house. The third time Napa just said never mind and refunded my money LOL. I depleted their stock that day.
If I need a mechanical pump these days I use either RobbMC or I'll buy a Holley mechanical from summit or something similar. I'm more curious as to why your carb is so sensitive to pressures above 5 psi.

As an example I run a summit brand Holley style mechanical on the nomad. I believe it's the 90 gph version but doesn't require a regulator. On cold start it has 9psi and it runs perfectly fine. After driving a bit and things get warmed up it drops to 7 psi and stays there. I consider this perfectly normal and the car drives and functions as it should.

I don't know what the cutoff point is where the carb is overwhelmed. Spec is supposed to be around 6 to 7 PSI max on the pump I used. It was actually putting out over 8 PSI and that was too much for both of the quadrajets I have. The other fuel pump I have puts out 5 PSI from the engine that runs well (with either of the quadrajets). I have no doubt some carbs will tolerate higher PSI that others, but from what I've read around 4.5 to 5 PSI is recommended for street use and it seems to work for me. Over 8 PSI is too much.