Holley 750DP idling issue since rebuild

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Bl1zzard

Bl1zzard

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I have a 1974 Swinger with a 360 bored .030" and a Edlebrock intake. I have a Holley 750DP that I've rebuilt twice now. The first time, I screwed around with the setup and installed a power valve on the secondaries and opened the secondary idle a little. It ran way too rich and idled poorly.
I rebuilt it again this spring and put the power valve blank plug back on the secondaries and left them closed. It idles much smoother, not rich at all. But a new problem has crept up. After warming up the idle is good, but after driving it for a while it starts to stumble at stop lights or backing up. Then it's really hard to start again. It almost feels like it runs out of gas. I put a new fuel filter on when I rebuilt it, filled up with premium.
It has a new tank so I don't think it's anything with the fuel system, just the carb. Thoughts? Suggestions?
 
Just for sake of doing it pull the needle and seat assemblies, clean em and put it back together with proper set float heights. But what is fuel pressure , is it a dead head system,? Easy enough to see if it's flooding or starving. But ive found that messing with filters and lines can often jar loose something to mess up the needle and seat. Good luck.
 
Fuel pressure is good, steady 6lbs. It's a new fuel pump too since the gas tank was changed out. I'll check the needled and seats. I did check the float height after the rebuild and it was set at the recommended slight trickle on my level garage floor. Thanks.
 
Another thing you can try that will at least tell you rich or lean is when it;s running badly, close the choke slowly and see if it clears up. If it does, you know it's a lean condition and richening it up with the choke straightened it out some. If it makes it worse, you know it's rich. At least then you'd know a direction.
 
If the fuel system is good the fuel could be perculating in the fuel pump when the motor is hot. A fuel filter with the return line filter will cure this. Today's gas vaporizes at a much lower temperature than the good old days.
 
Hopefully your timing is in a good place. Last place you need to mess with is the secd. side right now.

How much cam is in the engine and what's the jetting frt/back. Vacuum numbers maybe?

A hot/failing coil can cause issues like that too.
 
When it dies, activate the t/linkage & see if you are getting fuel squirting from the acc pump nozzles.
No fuel could be fuel percolation in the bowls OR no fuel getting to the bowls because the filter is blocked etc
If you get the squirt, then most likely flooding. Easy fixed with an Edel carb....
 
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