backward Holley issues
Fleet Mechanic
Joined: Nov 2002
Posts: 1,643
Likes: 69
the_hetz, I am one of those guys who advocate increasing squirter size on the 390 cure stumbles. Would you mind sharing what size IFR and IAB restrictions you used to cure the problem. Also, since not all 390s were calibrated with the same restrictions from the factory will you please list the OEM size you started out from? Did you replace the fixed air bleeds with screw-in air bleeds? Many thanks.
Also on a related issue I am having a launch hesitation with a drag car that uses three 350 Holley 2Vs (750 cfm 4V equivalent) where the carbs are mounted sideways on a common plenum. Have you ever staggered the restrictions front-to-back on each carb to counter the G loading effects on the fuel level? I have to be able to go from idle to full WOT in miliseconds on Pro Tree on a relatively cold engine. I've never seen this solution discussed. Thanks again
Also on a related issue I am having a launch hesitation with a drag car that uses three 350 Holley 2Vs (750 cfm 4V equivalent) where the carbs are mounted sideways on a common plenum. Have you ever staggered the restrictions front-to-back on each carb to counter the G loading effects on the fuel level? I have to be able to go from idle to full WOT in miliseconds on Pro Tree on a relatively cold engine. I've never seen this solution discussed. Thanks again
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Lead Driver
Joined: Mar 2008
Posts: 7,192
Likes: 384
From: Near Los Angeles
the_hetz, I am one of those guys who advocate increasing squirter size on the 390 cure stumbles. Would you mind sharing what size IFR and IAB restrictions you used to cure the problem. Also, since not all 390s were calibrated with the same restrictions from the factory will you please list the OEM size you started out from? Did you replace the fixed air bleeds with screw-in air bleeds? Many thanks.
Also on a related issue I am having a launch hesitation with a drag car that uses three 350 Holley 2Vs (750 cfm 4V equivalent) where the carbs are mounted sideways on a common plenum. Have you ever staggered the restrictions front-to-back on each carb to counter the G loading effects on the fuel level? I have to be able to go from idle to full WOT in miliseconds on Pro Tree on a relatively cold engine. I've never seen this solution discussed. Thanks again
Also on a related issue I am having a launch hesitation with a drag car that uses three 350 Holley 2Vs (750 cfm 4V equivalent) where the carbs are mounted sideways on a common plenum. Have you ever staggered the restrictions front-to-back on each carb to counter the G loading effects on the fuel level? I have to be able to go from idle to full WOT in miliseconds on Pro Tree on a relatively cold engine. I've never seen this solution discussed. Thanks again
The only carb that I have calibrated by narrowing and or enlarging bleeds was a Quadrajet. The guru for QJ's is Cliff Ruggles. He has a site and his own forum for QJ issues.
Tuned
Joined: Mar 2004
Posts: 412
Likes: 3
the_hetz, I am one of those guys who advocate increasing squirter size on the 390 cure stumbles. Would you mind sharing what size IFR and IAB restrictions you used to cure the problem. Also, since not all 390s were calibrated with the same restrictions from the factory will you please list the OEM size you started out from? Did you replace the fixed air bleeds with screw-in air bleeds? Many thanks.
Also on a related issue I am having a launch hesitation with a drag car that uses three 350 Holley 2Vs (750 cfm 4V equivalent) where the carbs are mounted sideways on a common plenum. Have you ever staggered the restrictions front-to-back on each carb to counter the G loading effects on the fuel level? I have to be able to go from idle to full WOT in miliseconds on Pro Tree on a relatively cold engine. I've never seen this solution discussed. Thanks again
Also on a related issue I am having a launch hesitation with a drag car that uses three 350 Holley 2Vs (750 cfm 4V equivalent) where the carbs are mounted sideways on a common plenum. Have you ever staggered the restrictions front-to-back on each carb to counter the G loading effects on the fuel level? I have to be able to go from idle to full WOT in miliseconds on Pro Tree on a relatively cold engine. I've never seen this solution discussed. Thanks again
I chased this around quite a bit before finally learning more about the iab/ifr adjustment. Every time I went up or down in squirter sizes I felt like I was getting somewhere for about an hour, then I'd get that weak spot again. Finally going up from .028" to .031" with a pin vise cured it and I was able to stick in a smaller squirter as well. I have a carburetor that already has screw in bleeds so I just bought some of equal size and drilled them out...getting a couple drill bits and buying a 10 pack of orifices is cheaper than getting an array of sizes.
I haven't had a 390 Holley and the squirter size very well maybe a full fix for it. I do not know how they tend to run, but wanted to give some generic tuning advice for something to think about.
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Lead Driver
Joined: Mar 2008
Posts: 7,192
Likes: 384
From: Near Los Angeles
Sometimes it is the simple things that need to be checked. I had turned my carb so the primaries were toward the firewall. The engine or the cliffy intake leans down in the rear. That meant that my float level was off, way high. I tried to turn it the accepted way, with primaries toward the radiator, but my t. cable would bind and stick. Finally I turned the Clifford 4v adapter plate 90* and mounted the carb as on an Offy DP. I set the float level, tuned it with a vacuum gauge, set the idle to 700, checked the v. advance, and away I went.
Amazing how smooth it idles when all is kosher. I don't want to hurt anyone's feelings, but now with the carb dialed in and the hesitation gone, I'd say that full-blown acceleration with the ZF5 is a far cry less than with my tricked out C6. One was for racing, and this is a bruising, tough, truck trans with a fantastic over-drive. It is fun to drive and gives plenty of power, but race it is not by any means.
Amazing how smooth it idles when all is kosher. I don't want to hurt anyone's feelings, but now with the carb dialed in and the hesitation gone, I'd say that full-blown acceleration with the ZF5 is a far cry less than with my tricked out C6. One was for racing, and this is a bruising, tough, truck trans with a fantastic over-drive. It is fun to drive and gives plenty of power, but race it is not by any means.
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