I can buy a brand new 4792 350 cfm from holley for center but they dont have the 500cfm 4789 amd 4790 outers. Looking at the 440 outers they are the exact same 500 cfm same body, same linkage, same style. I was told the jetting was the only difference and I can run it MrNorm did it with chevy tripower part numbers on there rare demon 340 six pack cars. Im running a hot cam .494/.513 & 268 /276 duration. Will running this setup work? I prefer to buy 3 brand new carbs then deplorable setup that need thousands more for rebuilding.
340 six pack carbs will this work? 440/340 combo
- Thread starter J.B.
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That’s what I did. The rear 340-6 carb has a distribution tab added in. I used the 440 out board carbs. Mine will be stroked so I’m not worried ether way.
Where can i buy the distribution tab?
33IMP
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In my opinion.... the 440 carbs will work fine.
Ok awesome thanks for help
You can’t.
You will be fine without a distribution tab in carb.
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33IMP
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Corvette carbs will work. So will Ford carbs, with proper mechanical linkage.
Sorry for the hijack.......What is a distribution tab?
It’s a little “L” shape tab that is (IIRC) riveted on the right rear carbs booster to help spread the air and fuel around a little better on the smaller displacement 340.
furrystump
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This, but where it is on the booster matters. So that is not the right placement for it.
Most have said i wont need it so gonna not worry about it unless i have an issue
furrystump
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Very true, six pack intakes are known for having crappy distribution, but that really is only a concern chasing every HP or if you have a very lean hole. Not a concern.
I like my Sixpack, but they can be a hand full tuning. Promax rear carb baseplate is a must. You cannot adj the front one and swap it out with the rear one and expect it to be right. 440 carbs are fine, just different metering plates, personally, I have the Promax plates in mine and just use Holley main jets. My lean cyl is #1.
The plate that uses jets is a must do in my book. Glad I did it. More precise.
It's great, but if You even sneeze tightening the base screws down, the throttle shaft starts dragging, the bushing clearance is so tight. Then the frt.&rr. Outboards don't open in unison. I spent hours w/a gram scale matching pairs of Holley springs to dial in the re-jetted set on an intake I'd blocked the heat to(iron), that tossed all that work out the window, with thin paper gaskets...soooo touchy..
Maybe so, but You have to make sure the float toes don't make contact w/those plates, thick bowl gaskets help...but if You fuss & tweak the screws once in a while to check them, they can start dragging on the way up or down. Fine while sitting still, then lean-surge/backfire romping, then smoking backed-down & coming to a stop.
They are very nice pieces, but one needs to be aware of these things, & take steps to check & mitigate them.
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Its found on OEM Carbs because they have the money to test for it and is designed to influence the air and fuel mixture to a particular side of the plenum to improve cylinder to cylinder distribution.
On the Holley's they are cast on the Carters they are riveted on. You can experiment with zip ties on the booster to replicate it
Thanks for the tip. I’m drawing a blank at the moment. Someone else makes those. Quickfuel I think? Those are the actual ones I have IIRC about who made them is correct.
Have you experienced any issues with them?
I’m also finding the rear base plate from Promax touchy to how much torque used to tighten them do is used. A real PIA.
They have you make a modification don't they? There is an interference? Between the body and throttle plate? Should remember, I have 2 of them on my engine. As far as sticking, you do have to open the throttle blades and check for interference before tightening. The two hole gaskets work best. I have open hole Mr Gasket on now, liked them better for idle adj, but am having a back to idle issue. Will have to wait for summer.
No, the "jet plate" simply replaces the metering plates, but they are a lot thicker, very nice units tho'. The baseplate works perfectly until You add just that touch too much torque, I saw no interference at the manifold at all, the throttles are the same size & placement. It seemed the shaft bushings are just so tight tolerance-wise, the slightest tweak in alignment from base screw torque made the shaft drag slightly. If there had been a bit more leeway, & low-drag shaft seals, it'd be great. When I worked on that project, it was like '04, the year the RedSox broke the "Curse of the Bambino"..I thought those jet plates were ProMax items, the baseplates I'm not certain tho', all came from them however.
My baseplates, front and rear were sensitive to position, blades were catching the gasket if not forward or back against the 4 mounting bolts. Concerning the exchange of the metering/Promax plates, also had to change the floats in the end carbs for jet clearance. Have been considering milling a slot between the 2 bores in the intake. My throttle shaft are are probably worn enough that they aren't sticking, but will check that.
Another thing, my 418 stroker was a monster until I installed quiet mufflers, too restrictive, but couldn't take the noise. Have a bog now, night a day difference between the mufflers. They want to breathe.
Guess that we have gotten a little off course here.
Another thing, my 418 stroker was a monster until I installed quiet mufflers, too restrictive, but couldn't take the noise. Have a bog now, night a day difference between the mufflers. They want to breathe.
Guess that we have gotten a little off course here.
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