Weber Jet Question
04-30-2012, 07:59 AM
#1
Weber Jet Question
I have a Weber 32/36 on my desmogged 83 Pickup. I have a Holley fuel pressure regulator with a gauge reading out to the recommended 3.5 PSI. I went through the lean best idle adjustment method and the pickup is running really well.
My mixture screw is set about 1 turn out (again still running well) and the idle speed screw is set about 1 3/4 in at around 850 RPMs. Timing is on the money at both idle and advance.
I re-read the lean best idle adjustment again and caught this:
My question for you all is that since I'm turned in on the mixture screw beyond the recommended 1 1/2 turns should I consider getting smaller jets?? From what I understand, Weber jets their carbs based on sea level tuning and I can't get much closer to sea level unless I dumped my truck in the ocean (I'm at about 25 ft). Should I go to smaller jets or leave it be? What would be the advantages or disadvantages of re-jetting or not re-jetting?
In my head, common sense tells me that if I'm restricting flow to the jets too much with the mixture screw that it would cause more "Gaps" in fuel flow through the jets which could prohibit optimum performance. Does this make sense?
Thanks for your input!
My mixture screw is set about 1 turn out (again still running well) and the idle speed screw is set about 1 3/4 in at around 850 RPMs. Timing is on the money at both idle and advance.
I re-read the lean best idle adjustment again and caught this:
Simple Rules for low speed calibration
If the mixture screw is more than 2 1/2 turns out turns then the Idle jet is too lean (too Small). When the mixture screw is less than 11/2 then the Idle jet is too rich (too large). These assumptions are based on the fact that the speed screw setting is not opened more than 11/2 turns. If the speed screw has to be opened 2 or more turns then this is also an indication of a lean condition usually requiring greater change. At times it may appear to be showing signs of richness or flooding it is really a lean condition. See pictures and notes in the tech 2 article supplied in the kit instructions, view and please understand the need to keep throttle plate as near to closed as possible so as not to prematurely expose the transition holes. This is what causes the visible rich condition, and confirms the need to increase the jet size.
If the mixture screw is more than 2 1/2 turns out turns then the Idle jet is too lean (too Small). When the mixture screw is less than 11/2 then the Idle jet is too rich (too large). These assumptions are based on the fact that the speed screw setting is not opened more than 11/2 turns. If the speed screw has to be opened 2 or more turns then this is also an indication of a lean condition usually requiring greater change. At times it may appear to be showing signs of richness or flooding it is really a lean condition. See pictures and notes in the tech 2 article supplied in the kit instructions, view and please understand the need to keep throttle plate as near to closed as possible so as not to prematurely expose the transition holes. This is what causes the visible rich condition, and confirms the need to increase the jet size.
In my head, common sense tells me that if I'm restricting flow to the jets too much with the mixture screw that it would cause more "Gaps" in fuel flow through the jets which could prohibit optimum performance. Does this make sense?
Thanks for your input!
04-30-2012, 04:30 PM
#2
Registered User
If you want the best fuel mileage and smoothest acceleration, you should try smaller jet in both sides of the carb. If you're satisfied with the way it's running now, you could probably get away with leaving it be.
12-29-2013, 01:25 AM
#4
Registered User
Remember, the Weber idle jets and idle mixture screw are handing fuel / air mixture not just fuel. So if you are closed in that far then yes, decrease your idle jet by one size and open the mixture screw more and see how it runs. You really need to drive the truck to see how it runs. Just because it idles well does not mean it will drive well. The idle jets handle fuel delivery up to 20-25% running so you need to drive the truck under load to see if the idle jets are close. If you have access to a Wideband Oxygen sensor / gauge it will make it easier to adjust the carb.
01-01-2014, 07:38 PM
#5
Registered User
Also, unless you're flooring it a bunch, you're likely not even opening the secondary very much. Most of the mixture is being handled by the idle jets on the 22r(assuming that's what you have and not a 20r). Start with idle jets, test drive it as Suncomb says, and see if it helps the rich condition. If it's rich up to around 3k rpms, go another smaller idle jets. Notice I keep saying jets, plural, even though it's a progressive carb, when the secondary does open it uses the secondary idle jet to transition til the full opening.
If it tends to richen above 2500 to 3k rpms, then start changing main jets.
It may take some time and testing, but once you get it you'll get quite a bit of satisfaction out of it.
If it tends to richen above 2500 to 3k rpms, then start changing main jets.
It may take some time and testing, but once you get it you'll get quite a bit of satisfaction out of it.
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