Economizer Valves in 94 Carbs

[B_man_Al]

Can someone tell me how these things work, what they do and how to determine if they are bad? The one in my carb (torn down on the bench) seems to have two positions (like a switch) at the bottom of the float bowl.

Al

[ken ct]

It should not be like a switch,unless its getting caught on something in the bowl.Should spring up and down very freely.It opens when a certain vacume # is reached.Will open and let gas into the system at like 7" vacume 6" of vac. 5" of vac. etc. etc. 7.5's open too quick. I use 5.5 ones in most of my rebuilds .You go down lower for multiple carbs like 4.5 or 3.5. ken ct. You can suck on the bottom side [where you can see diafram] and feel with one of your fingers on the other end and see if it holds vacume.Kind of a tasty thing on used ones . Lot easier on new PV.LOL

[Ralph Moore]

Just a dab of Bubba's hot sauce will take care of that!LOL

[ford38v8]

Originally Posted by ken ct

ken ct. You can suck on the bottom side [where you can see diafram] and feel with one of your fingers on the other end and see if it holds vacume.Kind of a tasty thing on used ones . Lot easier on new PV.LOL

Ken, the "suck it" test is done with the tongue. If it holds to your tongue, it's a keeper. Also, the tastiest valves are those that are sucked on after a healthy swig of tequilla.

Al, The operation of the power valve is the second response to a call for accelleration. The first response is the action of the accelerator pump, which immediately squirts a double shot down the throat. The economizer (power) valve becomes operational as the engine vacuum drops, thereby opening that valve, which delivers a continuing supply of fuel until the vacuum levels out, indicating the returning balance of air/fuel supply.

As Ken has written, some experimentation with different power valve values can optimize your system's response. Your main jets diameter, if undersize, can also have a pronounced negative effect at accelleration. Jets are the only adjustment of fuel/air ratio, while the two idle adjustment valves at the rear of the carb are used only to set idle, and have little effect on the carb at speed.

[Old Henry]

I don't know as much about carburetors as ken ct but this I do know about the Holley 94: (See third section for info particularly about the power or "economizer" valve)

Idle Fuel Supply

The fuel from the carburetor bowel passes through the main metering jet into the idle tube F (see arrows, Fig 7). Air is introduced into the fuel system by the idle air bleed A and a small additional amount of air is bled in by a small hole B in the aspirating nozzle (see insert, Fig 7). The idle mixture goes around the aspirating nozzle by means of an undercut around it’s outside diameter’ as shown. The mixture then travels down the idle passages C to the idle discharge holes D and E.
When the engine is to a speed of 350 rpm; the mixture is discharged out of the lower hole E only. As the throttle plate opens and the speed is increased, the upper D starts discharging. In this carburetor the lower holes only discharge from idle to about 450 rpm. The upper holes very gradually start discharging, in addition to the lower holes, from about 450 rpm to 1250 rpm. The action and timing are such that the upper discharge holes gradually start to feed, reach a maximum about 750 rpm, and then gradually become less effective as the main nozzle starts.
The lower discharge holes are provided with an idle mixture adjustment. Turning the needle out gives a richer mixture and in, a leaner mixture. The idle adjustments should be set for the highest and steadiest vacuum reading. The idle adjustment should not be jammed against the seat hard enough to groove the point. If this occurs the adjusting screws will have to be replaced in order to obtain a satisfactory idle adjustment.



Main Fuel Supply


As the idle system becomes less effective, the main nozzle G starts to deliver fuel. This occurs at about 900 rpm. Between 900 rpm and 1250 rpm there is a definite blend of the idle system and the main metering system. The power valve remains closed in this range, and up to approximately 3800 rpm except under load, which causes the manifold vacuum to drop. In this range all the fuel passes through the main jets (see fig 8), up through the main vertical well, then up and around the idle tube. The main fuel is emulsified by air entering at the main fuel supply air bleed H which lightens the fuel and makes the mixture more responsive to throttle changes. The mixture is again aspirated by the aspiration nozzle as it starts down the main nozzle G.


Power Fuel Supply

The power valve J (see Fig 9) is operated by the vacuum below the throttle plate through passage L, and the power valve spring K. At idle, the vacuum is the highest and decreases as the load increases. The diaphragm (actuated by vacuum) holds the power valve on its seat until the vacuum drops to from 8 1/2" to 9" of mercury where it is not high enough to resist the action of the spring. This point, at level road running at a constant speed is approximately 3800 rpm.
Under load as in climbing hills, etc., the vacuum drops as it becomes necessary to open the throttle wider in order to maintain speed. When the vacuum drops to from 8 1/2" to 9" of mercury, the power valve is opened by the spring, as when the engine speed exceeds 3800 rpm on level road, and the fuel then flows into the power valve and the channels and through the high speed gas restrictions into the center or main vertical well M (see arrows, Fig 9); this gives the additional fuel required for high speeds and for heavy loads at full throttle and low speeds.



This info extracted from: http://www.flatheadv8.org/holley94.htm

[ken ct]

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Good work Henry,i didnt want to get into a full blown explination.Plus i cant do pics. Thanks. Normally i use for a single carb situation. as follows 5.5 PV, .049 main jets [true .049's] and 7/8 to 1 turn out on idle mix screws.Leather accel. pump and steel inlet needle.All USA made parts.NO rubber China made parts in them. Combo's work for me. Lower PV's like 4.5 or 3.5 must be used with multiple carbs [2x2] and smaller MJ's .046. OMO ken ct.

[B_man_Al]

Thanks all for your inputs on this. Mine was stuck, so I worked it a while with some oil and got it free'd up. It now takes about 350 grams of force (up side down on gramas cooking scale) to seat the valve and it travels about 1/16" .... does this sound about right?

Al

[ken ct]

The oil you put in there is going to eat up the rubber coated diafram in there sooner or later. Big mistake. ken ct.

[B_man_Al]

Thanks for the scoop Ken . I'm going to soak it in soapy water for a while and then blow it out. I think its done anyway as it appears to leak at the diaphram.

Al

[ford38v8]

Al, blowing it out with an air gun would be another mistake. The diaphram is fragile and would rupture. If you can't get it to hold to your tongue with suction, it's a gonner anyway.

[Shu47]

Thanks for the detailed expaination Old Henry. I kinda knew most of this but your input really clarified the complete workings.

[Gumpy]

thank you henry for the diagram gump

[Charlie ny]

B man,
A genuine USA made Holley PV can be purchased at any speed
shop...just tell the guy you want a 4.5 or 5.5. The number is the inches of
mercury vacuum required to HOLD IT CLOSED. With genuine Holley pv's
you will be required to do a little relief work in the bowl.....I use an end mill
but a carefully guided Dremmel cutter will do just fine. The brass ring on
the stem of the new Holley pv's interferes with the small relief in the bowl.
At $15 it's just too cheap to run a used one.
Try to find the correct gasket to use between the bowl and pv.
Best results with a .040 thick x .505 hole x .750 outside dia. Ken and I
both have these gaskets if you have no luck elsewhere. The big gasket
that's supplied (with the triangular hole) doesn't seal real well and over
time will start weeping.

Charlie ny

[Old Henry]

Originally Posted by B_man_Al

I think its done anyway as it appears to leak at the diaphram.

You don't need to try too hard to fix it. You can get a new one for under $10.00 here: http://macsautoparts.com/early-v8-ca...0R3CHL1072173/