I have an 850 holley with air bleeds and 4 corner idle on a 383 sbc . I have a wide band air fuel meter. the problem is if i set the idle to 13 to 1 afr the air mixture screws are only out about 1/2 turn , i have not went full throttle yet but at cruise it goes right from 13 to 1 to 18 to 1 and then a little more throttle it goes right back to 13 to 1 or richer , this is my first time with a wideband and air bleeds. if i put in a bigger idle air bleed and turn the idle screws out will this leval things out, or do i have to mess with the jets in the metering blocks there is an idle jet and then there is just one jet in the 4 or 5 other holes i think it is the second hole from the bottom, any help to get me going i the right direction would be great. thanks!

 

not familiar with that carb, but general questions:

timing at idle?
throttle blade position? do you have transition slots in the throttle bores?
PCV valve being used at all?

 

I'd check out the power valve first. What's vacuum doing when MR takes a dive? If it's above your PV #, you need a larger # PV.

 

timing at idle 14 deg. no pcv valve,dont know what transition slots are? My power valve is a 4.5 i will have to check my vacuum, but i dont want my power valve open at low throttle do i.

 

timing at idle 14 deg. no pcv valve,dont know what transition slots are? My power valve is a 4.5 i will have to check my vacuum, but i dont want my power valve open at low throttle do i. Why is there only one jet on each side for the emolshion circuit ( i think that is what it is ) its in the second hole from the bottom, the other 3 or 4 holes on each side are just threaded. should i try taking that jet out or moving it? Thank you for the help.

 

You don't want the power valve to open at cruise. You do want it open when you come off idle. You probably need more like a 6.5 or 7.5 PV.

 

how can i get my power valve to open coming off idle,maybe 1500 rpm but close at highway speed 2500 rpm? thank you!

 

your power valve open when you mash the throttle, and your vacuum level drops. If I understand holleys correctly.

Your non powervalve system, your standard jets and whatnot, should have enough flow to keep your car running nice and smooth before you mash the throttle. Read vacuum level, while idling, in gear if you can.
Then get the power valve below that. I think you take your vacuum level, than half it, then subtract one, to get the PV you want. So if you have 14" vac at idle, you'd want roughly a 6 power valve. IIRC, I might be wrong however.

 

Vacuum drops as the throttle opens. As RPMs rise at a given throttle opening, vacuum will rise.

You need the PV to open off-idle to avoid a dead spot. Under cruise conditions, vacuum will be high enough to close the PV. Choosing the PV so that it opens at high enough of a vacuum off-idle to avoid the dead spot, and closes at low enough of a vacuum at cruise to maintain fuel economy is the goal. A 6.5 usually covers those bases with the typical street engine. A 4.5 is good for getting you killed pulling out to make a left turn at a busy intersection.

 

Power valve selection.
Take a vacuum reading AT IDLE...say that number is 8. Divide by 2 then add point 5.
Using the above number would require a 4.5 power valve
This will be your starting point.

 

The "official" Holley method:

"The power enrichment system supplies additional fuel to the main system during heavy load or full power situations. Holley carburetors utilize a vacuum operated power enrichment system and a selection of power valves is available to “time” this system’s operation to your specific needs. Each Holley power valve is stamped with a number to indicate the vacuum opening point. For example, the number “65” indicates that the power valve will open when the engine vacuum drops to 6.5" or below. An accurate vacuum gauge, such as Holley P/N 26-501, should be used when determining the correct power valve to use. A competition or race engine which has a long duration high overlap camshaft will have low manifold vacuum at idle speeds. If the vehicle has a manual transmission, take the vacuum reading with the engine thoroughly warmed up and at idle. If the vehicle is equipped with an automatic transmission, take the vacuum reading with the engine thoroughly warmed up and idling in gear. In either case, the power valve selected should be 1/2 the intake manifold vacuum reading taken. EXAMPLE: 13” Hg vacuum reading divided by 2 = 6.5 power valve. If your reading divided by 2 lands on an even number you should select the next lowest power valve. EXAMPLE: 8” Hg vacuum reading divided by 2 = 4 power valve. Since there is no #4 power valve you should use a 3.5."

From http://www.holley.com/data/TechServi...wer_valves.pdf

 

i just checked my vacuum at idle it is 16 in neutral and 13 in gear, i will try a 6.5 power valve. If i only need my idle air screws out 1/4 turn should i reduce the idle feed restrictors or increse the idle air bleeds. Thanks for the help.

 

hello,

this is some thing that should be adressed
each circut plate should have 2 jets

later

rick king

 

what do you mean by circut plate, are you talking metering block? If you are there are 2 restrictors in each metering block, what does it do if you move the jet to a higher or lower hole? THANK YOU!

 

yea mettering block
I had a brain fart last night, i believe that I am off topic
sorry


on all the holley carbs that I have seen there is only to places for the jets and they are side by side not one on top of the other.

later
and

gb

rk

 

Im not talking about the main jets,in the metering block, i think it is the emolishion passages they are threaded, and only one hole on each side has a restrictor. find a picture of a proform metering block and some holley hp blocks, there are 4 holes threaded about one inch on each side of the power valve going up .