Howdy!

Issues with my new ( used carb ) I picked this up 2 months ago and just now did the swap...removed a Carter from my fairly stock 460 in my 1977 F250. Stock intake, exhaust, mild cam ( not sure about the specs )

The carb is a 3310 - dual feed, vac secondaries, manual choke. Primary jets are 68 ( factory is 70 ) secondary metering plate is a 21 ( stock ) Pump discharge nozzle is a .035 ( factory is .031 and I may need to drop back to stock size )...not sure about the power valve. This carb is about a year old and was installed originally and tweaked for a 454 in a monte carlo that I guy was running on street/strip.

Here is the problem. I did the install...no problems. The previous owner had pulled both needle valves loose to dump the fuel prior to shipping so I initally had fuel all over the place. I turned them both way down ( too far ) to control the fuel level. The truck sat and idled perfectly...no smoke...perfectly smooth idle. Reving the engine provided quick and crisp throttle response with no lag or bogging. There was a bit of hesitation, after reving the engine, when the RPMs come back down to near idle....it wants to hesitate momentairly ( almost non existant) which makes me think the discharge nozzle is a touch too big...only does this if you crack it open and closed really fast...so I suppose it is loading up just a bit. If you open and close it slower, this is not an issue at all.

So I took her for a test run. Out of my drive way and down the road proved the carb to be tuned pretty well. Smooth transition from idle through the secondary opening and to WOT...a half mile down the road it fell flat on its face and died. I pulled into a drive way, cranked a little and it popped right off. So I figured it was starving for fuel due to the floats being set too low. I knocked the lock screw loose on the primary bowl and gave the valve a turn or so out...locked it back down. Started it again...popped right off...drove her back toward home...and it loaded up..black smoke...I stopped and found fuel all over the place again. I Turned the valve back in a spin and took it home.

This time I pulled both site plugs in the primary and secondary bowl and properly adjusted the floats. Sat and idled perfectly again. Went for a nother spin...same thing happened...a half mile down the road it fell flat on its face...had to be a lean condition as there was no smoke and no fuel. I backed off the throttle...and it idled this time...I let it continue to idle for 10-15 seconds then got into the throttle again and it ran great for 20 seconds or so then fell on its face again. This is what it continues to do. If you let it "catch up" it will run like crazy....till it appears to starve for fuel.

So this is my theory. There isn't enough fuel pressure.... clogged fuel filter ??? It will idle fine....and if you are driving around with minimal throttle it will drive a long time before there is an issue ( if there is one at all )...open it up or run it 60 and it wants to die...I suppose the bowls aren't filling fast enough at highway speeds or heavy throttle conditions.

I am not a carb tuner...in fact this is the first Holley I have ever messed with at all. Briggs and Stratton are bad enough.

Does my theory sound correct? I wasn't having this problem with the Carter carb I replaced ( just a few others....) What should the fuel pressure be?

If I haven't given enough info, please let me know!

 

That sounds correct. You should have around 6psi of fuel pressure. You could have a weak pump, clogged filter, or even possibly a dry-rotted rubber line from the gas tank to the frame allowing air to be sucked into the line. Does it do this with the engine cold as well as hot? If only hot, you may have a vaporlock issue and may need to insulate the metal fuel line around the engine.

 

I swapped the fuel pump last night, tweaked the idle mixture screws a tad...runs like crazy.

 

Glad to hear you got it fixed