Holley 750 Carb Help

[burksde]

OK folks, I have a carb question that I would like to see if you all can help me out with.
I have a 67 pick up with a 383, holley 750 vacuum secondary and a manual holley fuel pump. I have had the same pump and card now for about 5 years and only filters changed. No problems.
After a recent rebuild that took 2 ½ years (to include the fuel system) I though it would be best to rebuild the card and replace the filters. When I got the carb back from the boil/rebuild I was told that I had water in the carb. But all else looked good just needed a good cleaning.
I went home drained the tank, refilled with good gas and drained fuel lines by taking the fuel line off the outlet side of fuel and turning the engine over. Good right?
I reinstalled the carb and it fired right up and ran GREAT. Pulls hard for ever without a hiccup. BUT, when I let off the gas and GET back to cruising speed, as I apply the throttle to sustain cruising speed, the engine cuts out..let off the gas it is fine…give gas (even just a little) and engine cuts out. (this all happens only after getting on it “hard”) After about 5 or 10 seconds all is fine and I can cruise all day…get into again and it all repeats… I was thinking floats..I came home and adjusted them..took it back out and same thing….Now I’m thinking metering block.. The guy who boiled and rebuilt the carb said bring it back by so he can look at it..I just have not had the time (I work from 1500 till about 0400) …So I thought I would try my luck here. Thanks for any help and sorry for the long se-nops o

[67shortie]

Couple of things here, it's either lean or rich so let's look at both.

Rich, too much fuel. Do you see black smoke out back when the throttle is mashed? Coming off of a full throttle run, could be too much fuel in the secondaries temporarily flooding the engine. Sticky needle and seat in the secondary fuel bowl?

Lean, draining the fuel bowls. Do you know what your fuel pump pressure is? If it is low, it will allow the engine enough fuel for light cruise but when pushed it will not supply enough to keep them full. So, when you get back to cruise the engine does not have any gas in the bowls to run. And what you say about having to wait a few seconds the pump refills and your on your way again this may be the culprit here. Also something to check, kinks in the supply line, bad fuel filter (even new it happens) or a clogged line or sock in the tank. The best way to check this would be fuel pressure at the carb or a temporary guage OUTSIDE the cab like on the hood (I don't like fuel pressure guages inside unless electric)

That's all I can think of right now

[72 Cheyenne402]

I had the same carb on my truck. I had a problem with getting some trash in the neddle seat and flooding out. Also I had to replace my plastic floats with brass floats that seemed to help. I replace the carb with a 750 AFB and have not had any problems sence. My 750 holley is up for sale!

[MrC1]

Agree with the above comments. I've also seen some funny things where a worn shaft caused some weird issues. I think this one's pretty doubtful, but it's possible that when engaging the secondaries, the shaft is shifting a little causeing the throttle blades to be cocked out of position.

In reading what I just typed, sounds to me like I'm saying your truck might need some viagra.

Other than that, I recommend having a not-so-good friend ride under the hood while you do some WOT runs to see what's going on. Okay, I'l go away now.

[burksde]

Thanks for in put guys. I was thinking the same thing about the bowls sucking dry. I see no smoke at all and was wondering the same thing (to lean) As for the Holley, they run best wide open I know and are a pain in the rear at times, but it is just family tradition..lol I have ofetn looked into the AFB but could not turn my back on Holley..thanks though guys I will look into your input.all helps at this point.