Carter HV Fuel Pump Pressure Loss

Hey folks, having an interesting issue with a setup I just put together, and seem to be having an issue with the fuel system. The car when cold runs and starts fine, fuel PSI is sitting good at 4.5psi. As the engine warms, the pressure falls until it goose-eggs and the engine starves and dies. Was hoping it was just a pump that died from sitting, however a pump swap had the same results. Idled fine for about 4-5 minutes and the pressure slowly fell off again until it died. I'm inclined to drop the tank as it's the only thing that is more than 2 years old. Any other places to look or suggestions before I crack the thing open?
Engine is a 440, all iron, mild cam. Pump is mechanical.

Check the sock on the pickup tube if there is one. Disconnect fuel line at both ends & blow the line out. Might be a restriction.

Blew the lines out, no change. Gravity feed flow was pretty good. It really seems to be temp/pump related. I'm thinking of picking up a junky parts store pump and checking the pump rod for length. wondering if it might be short or sticking?

I assumed you checked the filter.. next thing..
if you have the stock sock in the tank take the
fuel cap off and blow shop air into the pick up
tube to blow the sock off... final thing is the
vent.. make sure its open and you have enough
vent for the power
If it does it at idle.. open the gas cap and see
if it will do it

check venting

Checked the filter, it was good but nuked the o-ring on disassembly (XRP rebuild-able) Swapped in a new one.
Blew the lines out with the cap on and off, blew a bunch of fuel out. Have tried idling it with cap on and off, no change.

Pump rod might be shot. That can drive you nuts looking for the problem.

I'm going to check that first thing tomorrow. I'm afraid for that and the cam eccentric. It's pretty much come down to:
-Push Rod / Cam Eccentric
(anyone know what the "throw" is supposed to be?)
-Pump type
(Pump one came off of a running 383 and pump two came off of a running 440; both had less than 5k miles on them)

I really doubt the rod or the eccentric are bad.. it wouldnt
build the pressure right away then drop... I think your
getting crap pumps. are they rebuilds
EDIT
I think its a heat related issue.. but maybe the eccentric
isnt turning when it start to warm up(the hole to big)

Doubt it's a heat soak problem with the engine running just that short amount of time. The pump is in its born location. Shouldn't get hot there.

×2 Mesiure the rod !

Pulled a known good rod and measured it (3.225) I'll pull the one out fo the running-ish motor tomorrow in the morning and report back; but...if the rod is wiped, wouldn't the same be for the eccentric?
But assuming I have a shorter rod; (they came in two lengths i believe) how would the warming up effect pressure output? It gets bounced back and forth like a floating valve or something?
As a note, after I swapped pumps, it "pumped up" the pressure as the system started drawing and then the needle would "tick"a half psi or so. If I revved it to 3k or so, the pressure would hold steady.

Also to note; it's a completely cast iron engine and I'm in Southern AZ, so today's ambient temp was 108ish. However, the cooling on this and all my cars is/are exceptional and this thing would/could/did idle for 20 minutes in the sun and never went over 196* when I was stress testing the heat system a couple of weeks ago. That and fuel supply was adequate to do that testing.
Frustrating but fun!

Just to be sure it's not a problem from the fuel pump back, have you tried sticking the intake on the fuel pump in a jug of gas to rule out likes/socks/tank issues?

Just pulled the rod. I'm going to go ahead and say the rod is wiped. Well grooved on the Cam end and only measuring 2.991" at it's shortest point. So now the question is...if it ate the pushrod; do I slam in this fresh rod and keep my fingers crossed, or is safe to say the cam eccentric is wiped too? And does anyone know the amount of lift the eccentric is supposed to give so I could run a quick measurement?

Been so long since I worked on a BB but is the
eccentric built on the cam or is it a add on like
the SB

It's made onto the cam.

I believe it's built into the cam, between the front Bearing surface and the Oil Pump/Dizzy drive gear.

Measure the diameter of the rod and find something
close to it but longer so it sticks out of the pump
mount and see how much movement you get from the rod
and hope the eccentric is ok... good luck... or its
time for a electric pump
EDIT
A transfer punch might be long enough(dont put
the pointed end in )

I already loaded the good rod in and coated it with assembly lube. I"m going to depth gauge it when my guys get in this morning. I couldn't roll the engine over and hold the gauge by myself.

I was hoping someone would know the lobe height.

The two wear together...... Or live together.

You can put a new/different rod in it, but you'll be on borrowed time.

You didn't say what type of cam you have, but I'm assuming its a cast cam core.

If it's a billet core(roller cam), they don't often live when used with a std pushrod(although I did get away with it on my own motor).

Got impatient this morning and slammed it all together with the good rod. Cold fuel pressure was really good, drove it around on a few errands, no issues. As things warmed up pressure backed down to a steady 3 psi. I'll keep checking it as I drive it over the next couple of days.
It's a Comp Cam.
And the car used to be setup for an electric pump and full return system, so I have everything to convert it back, just don't like the limited life cycle of the electrics.

Are all the fuel lines tight and leak proof? Happened on an MG years ago, idled ok but under load it was suckin air or leaking either way new rubber line and clamps and problem solved........