Can anyone tell me what jets you run in your aftermarket Holley? I have a 1971 454 4spd, 9.6:1cr, stock exhaust, aftermarket dual plane, Holley 3310 (750 single pumper/vac. secondaries). The PO had a 50cc acelerator pump, plugged power valve, and other "racing" mods on this poor baby. I went back towards stock, but it seems to be jetted very rich. I had to lower the float level and almost shut off the idle screws to get it to idle. If I unplug a manifold vacuum line, it speeds up and smooths out nicely. Naturally, I failed to write down my jet size when I had everything apart. I thought I would order up some new Holley jets, but where to start?

Suppose I knew that main jet size doesn't affect idle quality, but suspected that since everything else was modified, then they probably were also.

Sounds like the PO really didn't know what he was doing, or was taken in by the counter person at Bubba's Speed and Marine, the reason why the carb is acting so rich is because the power valve circut has been pugged, when you plug the PVC the carb thinks it been jetted up 6-10 jet sizes, if he plugged both metering blocks it even fatter, you also don't need the big accel pump, I sugguest you start with the stock pump, 65P-85S power valves, 70P-76S jets and see what happens.

   The power valve circut is a transision circut from off idle to WOT, when you remove and plug the power valves in realality you are not plugging anything, you are actualy richining up the idle and off idle circut as well, some drag racers modify the carbs in this way so when they leave at 2500-3000 their engine is getting the air and gas it needs.anips38568.8279050926

Ahhhhh.....the old "block off the power valve" trick!
That's a good idea if your runnin a drag boat/car, but not at all cool for a streeter.
Anips is right on the money!



What's wrong with Bubba's Speed & Marine, tho?
I jest ordered up a jumbo-sized (50 lbs) can of vaccuum from them. Bubba sez it'll keep my headlites workin liken they oughta. Ya'll think I got tooken?

I heard that when Fat Dick left Bubba went out of biz, must have been a clearance sale.

Thanks for the info. I'll start with a stock Holley rebuild kit and get the smaller jets. I really appreciate having someplace to ask how things should be as I "de-Bubba-ize" this car.

[QUOTE=anips]the reason why the carb is acting so rich is because the power valve circut has been pugged, when you plug the PVC the carb thinks it been jetted up 6-10 jet sizes, if he plugged both metering blocks it even fatter, you also don't need the big accel pump, 
   The power valve circut is a transision circut from off idle to WOT, when you remove and plug the power valves in realality you are not plugging anything, you are actualy richining up the idle and off idle circut as well, some drag racers modify the carbs in this way so when they leave at 2500-3000 their engine is getting the air and gas it needs.[/QUOTE]

Sorry thats completely wrong.  I don't know who told you that, but plugging off the power valve(s) will not richen anything, plus carbs don't have the ability to compensate.

The reason racers plug off the power valve and its usually the rear one is during acceleration fuel rushes away from the power valve uncovering it.  When its uncovered there is no fuel to send through the circuit and you end up with a lean/flat spot in the fuel curve.  This the same reason they run jet extenstions in the rear fuel bowl as well.

So anytime you plug a power valve you have to go up 4 to 6 jet sizes to compensate for the fuel that is  not being allowed through the power valve circuit.  so plugging it does nothing but lean it out.  If its plugged it should be jetted up to richen it and the only way that happens is by someone putting larger jets in it.

There are several problems with this bubba carb.  One if there is a power valve in the rear he added a rear metering block, because the 3310 did not come with one it was only a plate.

Bubba added the 50cc squirter because he was needing a lot of extra fuel that a single squirter carb could not provide.

To get you back to a good stock out of the box starting point would be to do as anips said which is to put the 30cc pump back on, put 72 jets in the front, 75 jets in the rear, with 65 Hg power valves in the front and rear.  I would also put a yellow vacuum secondary spring in the secondaries make sure you have a .031 squirter noszle for the pump shot system. 

 

Shark is right and I was partley wrong, last year I blew a power valve, every thing got rich so I got the holley book out and read about the power valve circuit and why some people remove and plug it, usually when I reply to a post and not sure I try to find the artical in my vast storehouse of stuff going back 35 years, couldn't find the holley book or why racers plug the valve, did it from memory, I won't make that stupid mistake again, What I shoud have said was" Many tuners will remove the power valve and use a plug thinking its the hot ticket, however, if the PV is removed and plugged the main jet size must be increased 6-10 sizes to make up the required fuel lost by the removal of the PV. In addition when the PV circuit is plugged the part throttle economy is worsened and may become overly rich, plug fouling may become a problem at part throttle."-MorTec Holley Tuning Tips. As far as the rear metering block goes the first time I saw a 3310 maybe 35 years ago it came with metering blocks front and rear and I believe it was a 780 CfM, I bought two of them,one for my 53 super 88 stock car, and later one for for my first modified, now, this is from memory so don't quote me on that, now they are 750 with a plate
       

Wasn't trying to make a mockery of your information.  You were partly correct, but I did want to set the record straight for someone that might be a first time carb tuning attempt.  Nothing worse then getting ahold of a old carb and not knowing its history.  Its bad enough to not know much about carbs and then get one that has been completely reworked.  Might save a few bucks upfront, but in many cases you pay out the A@# in pain, frustration and money to make it work.

As far as your info about the 3310 you are correct, but the 780 cfm model is the original 3310, that was replaced by the current part number.  The part number on it was 0-9188.

Matthew,you got it right, I got it wrong, I'am just pissed at myself,whats important is Paul now has the right info as a starting point to take care of the problem.