hesitation during light throttle acceleration.....750 holley

[mbrooks]

Just an fyi, I ended up squaring the idle circuits, I ended up liking the .073 better than the .076, so far, and .031 on the ifr's. Should make the idle adjustment better with the circuit squared instead of varied. Went up to 78 on the main jets gave what looked like 13.5-14/1 on moderate acceleration before the pv came on prior using 76 gave 15-1, hsab at .031, with as issued emulsion 28 28 28 bl 28. Went to .055 on the primary t-slot only gave aprox 15/1 and higher cruise. Have yet to do the full throttle app to see when and how much the pv should come on. Should get you close in the ballpark.

[PRNDL]

Rewguy, did you ever resolve this?

[mbrooks]

Old thread with a request for solution, here is what I did.

I found an old holley 750 center pivot carb in the shed from a 400ci ford truck motor. I was told it ran like a striped ape. Go figure a 750 holley on a 400 truck motor. I duplicated this carb on a new holley hp series carb and my 351 and 408 ran great. I found the emulsion bleeds like to be .026, none of the new stuff uses these, I figure because they are little tougher to drill than the .028 that are used. Also the main circuit starts to pull right off idle with the air bleeds. There is no delay, and no hesitation. It was my impression that the new designed stuff forgot what the old designed stuff had figured out, somewhere the information was lost or people being people, think it can be done better. I don't have the information as it went with the cars it was used on. But if the old stuff is duplicated you'll find a good running setup. I had an a/f gauge on the 408 and with the main jets in the low 70s it still cruised a little rich but I didn't have leaner as I used them on the 351. I think the old carb had 71s or 72s. Don't remember the power valve but it came on perfect with the acceleration and richened up just great.

I think I also had to work on the carb butterflies to get it to idle down as I was using a vacuum advance also. And maybe had to notch to uncover the idle circuit. The butterflies just didn't fit the bores well enough to close them down.

[mbrooks]

Old thread with a request for solution, here is what I did.

I found an old holley 750 center pivot carb in the shed from a 400ci ford truck motor. I was told it ran like a striped ape. Go figure a 750 holley on a 400 truck motor. I duplicated this carb on a new holley hp series carb and my 351 and 408 ran great. I found the emulsion bleeds like to be .026, none of the new stuff uses these, I figure because they are little tougher to drill than the .028 that are used. Also the main circuit starts to pull right off idle with the air bleeds. There is no delay, and no hesitation. It was my impression that the new designed stuff forgot what the old designed stuff had figured out, somewhere the information was lost or people being people, think it can be done better. I don't have the information as it went with the cars it was used on. But if the old stuff is duplicated you'll find a good running setup. I had an a/f gauge on the 408 and with the main jets in the low 70s it still cruised a little rich but I didn't have leaner as I used them on the 351. I think the old carb had 71s or 72s. Don't remember the power valve but it came on perfect with the acceleration and richened up just great.

I think I also had to work on the carb butterflies to get it to idle down as I was using a vacuum advance also. And maybe had to notch to uncover the idle circuit. The butterflies just didn't fit the bores well enough to close them down.

Last sentence should have read had to notch the butterflies to uncover the transition circuit port, or t slot. The butterflies were chamfered so that when closed they mated to the surface of the bore, like the butterfly had a 45 on the edge instead of the 90, hence the notch to keep the t slot primed. The center air cleaner bolt idle adjustment works great for getting this accomplished and having the right relationship between the butterflies/bore/t slot.