[Fjguercio]

AS I have posted before..... time will tell

Lets see what the poster ends up with.... unlikely 140/145 run jets will work
Poster needs larger run jets and has already said his center #4 was lean... Larger Run Jets 145/150

If you look at the weber 34 thread you will see I am running 147.5/150 run jets and is what I am suggesting 147.5 pairs or 150 so they do not sell the 147.5 as a sole part number but put one 147/5 in the carb when shipped. How about that you say 140/145 runs well but too lean and I have been saying 147 is the sweet range all along.... TIME WILL TELL... poster if are reading my posts you should try the larger run jets


Do you get that..... most of the 258 carbs use 147 - 150 range run jets. Industry standard is to use metric drill bits for the carb jet holes. Thats why the numbers are the same.

[mcmud]

"I still think your secondary idle jet may be a little small and that's what I'd increase next. Maybe mcmud will correct me on this if I'm wrong as the majority of my experience is with the syncronous Webers."


Until the primary is tuned we can not judge the range of the secondary idle jet, nor the main in either.

While the Air Bleed orifice on the primary is calibrated to a hole sizes of 1.65mm the secondary Air orifice is only 0.65mm, this is why a typical set up will allow for the smaller secondary idle jet, normally a .015mm spread between the two.

Remember that on the progressive Weber that the secondary progression flow is activated only after and during the nozzle flow of the primary boost venturi and most often when the Accelerator jet has come into flow and typically with the Power Valve adding in support or very near to the draw.

Now if we find that the 75 primary is fitting to the OP then I would suggest that he install a 60 into the secondary for trial.

[swatson454]

Originally Posted by mcmud

Until the primary is tuned we can not judge the range of the secondary idle jet, nor the main in either.

While the Air Bleed orifice on the primary is calibrated to a hole sizes of 1.65mm the secondary Air orifice is only 0.65mm, this is why a typical set up will allow for the smaller secondary idle jet, normally a .015mm spread between the two.

Remember that on the progressive Weber that the secondary progression flow is activated only after and during the nozzle flow of the primary boost venturi and most often when the Accelerator jet has come into flow and typically with the Power Valve adding in support or very near to the draw.

Now if we find that the 75 primary is fitting to the OP then I would suggest that he install a 60 into the secondary for trial.

I see. Doesn't it also provide additional mixture volume at idle? I was hoping to get his throttle plates back in line without getting too fat on the primarys progression. That was my line of thinking anyways.

Thanks

[mcmud]

No Sir, on the progressive Weber the secondary only has Progression holes, no idle hole like on the synchronous 38 DGES or like the primary side of the DGEV.

[swatson454]

Originally Posted by mcmud

No Sir, on the progressive Weber the secondary only has Progression holes, no idle hole like on the synchronous 38 DGES or like the primary side of the DGEV.

Oh, savvy. Thanks for the clarification. Well it seems like the OP has two choices then. He can increase the idle jet on the primary to increase the mixture volume available below the throttle plate; which would be the correct way to do it.

Or he can start leaning out the main jet until virtually no fuel is available for a correct progression, ride around on the main circuit and depend completely on the PVEC to keep him just barely safe under a load. Of course he'll probably need a CDI ignition box as that will be nearly the only way that that excessively lean mixure has a chance of firing off and hope that his conservative timing curve will help. Lol!

[Fjguercio]

Originally Posted by swatson454

Oh, savvy. Thanks for the clarification. Well it seems like the OP has two choices then. He can increase the idle jet on the primary to increase the mixture volume available below the throttle plate; which would be the correct way to do it.

Or he can start leaning out the main jet until virtually no fuel is available for a correct progression, ride around on the main circuit and depend completely on the PVEC to keep him just barely safe under a load. Of course he'll probably need a CDI ignition box as that will be nearly the only way that that excessively lean mixure has a chance of firing off and hope that his conservative timing curve will help.

Prior we just diagreed on the first steps for reading the idle screw and the direction of change on idle jet changes.


But this statement is far from anything I would say or agree with. First the throttle plate is closed and the idle circuit work... we agree... When you use the gas pedal the throttle plates open, more air flow, and the run jet starts working. I say at the working of engine.... with throttle plates open and working most is run jet and 15% is the idle jet. I also feel you need to ck the statement that the idle circuite is 2/3 of the operation with gas pedal..... maybe when curise if the throttle plate is closed it a great deal of operation but I would have to see the throttle position... but still not likely.

There is no way the poster is going to leaner/smaller on runs than the 140/145 and if they talk you into this with lean plugs now esp the #4 run to Weber and get some help. Even if you have to pay for it. With your screw settings and this range of run jets you need to go up on each one by 1 step. You will also see with that change your mix screw will likely go to the 1.5 range rather than the 1.75 you posted.

Even the lean remark.... if you get that lean... the heat will be so high you many not need spark the engine temps will light off the fuel/air mix. Leaner burns easier than rich mixtures. Thats why light dust and light fuel mixes or what is sometimes called Vapor is so explosive and easy to ignite. Lean is hot, hot causes early fire and is called detonation.

AS for his conservative time curve.... I have to go back and look but he is a computer vinatge, not optimized or recurved, and starting off with high amounts of initial advance, 10/12 range is what you told him I believe. Yes the high initial can help him get the burnt fully and lit..... but initial advance does not come out and is not adjusted with engine needs like the vacuum advance and mechanical advance...... So computer advance with high initial advance number are not conservative, they do not correct for engine load and operation conditions. Toooo much initial time that does not adjust or change and is alway there with hwy cruise conditions is far from conservative. If anything it can cause high speed cruise issues, knock, and the need to use prem gas like Mike Romain has been saying he has to do.

[Fjguercio]

POST #3..... looks to be pretty close to what the out come is going to be.
145 to 150 run jets.... his 140/145 are too small.

Originally Posted by Fjguercio

4k - 5k is not that high... I grew up 3.2k.... First blush you Idle jet looks a bit big and your run jets look too small.


then let us know your screw settings.
I put a sharpe dot on the screw slot on one end... makes it easier to count turns and set back to original settings. Get a spiral bound note book and start writing stuff down.

Also pull your plugs and write down what each cylinder looks like. The one by rad is #1. Any soot should be cleaned off gently with wire brush and gap to .045 after team rush, aux grounds, use of copper antizeise on plug threads, Plugs can also clean with carb cleaner. Do your grounds and updates as some of the very first setps.

[IdahoJeeper]

Alrighty....I ordered up some jets (couple each, primary/secondary idle, main) tonight. Hopefully they will be here by the weekend and I'll have some more results to post up!!

[swatson454]

Don't you just love the UPS truck.

I must say that an 8in pull sounds interesting to me being that you're so close to being sized correctly with the idle jet. I'm wondering if you may have a case of the primary spring/bracket assembly being a touch too tight on the throttle shaft. Don't sweat it at the moment but if your new idle jet doesn't seem to do what it should, we might need to address that possibility.

Shawn

[uptillnow]

OP
“The installed jets are:
Primary / Secondary
Idle 70 / 55
Main 40 / 40
Air 160 / 170

Where I live is 4800' AMSL.

So my questions are:
1.) Do I change the Air jet (smaller) along with increasing the Idle jet or just change the Idle jet.
2.) How many sizes can I expect to move on the idle jet?
3.) Are the currently installed jets a good or correct "combo"?”

I have found, and also what is considered “Altitude” is when the volume of oxygen molecules within a cubic foot of air has diminished to the point at which the air fuel ratio becomes richer than that at normal “sea level” ratios. (3800ft to 4200ft) This richer mixture (less oxygen) just doesn’t burn as well.
So, if the volume of “fuel” at sea level is correct for your engine that gives an adequate bang or explosion, why wouldn’t you need the same volume fuel at altitude? This is where/when we need to add more air to support that fuel we know works at sea level. The Weber 32/36 DGEV “technically” can’t add more air to either low speed circuits. So (unfortunately) we are limited to reducing the volume of fuel in the idle circuit so we can still get that sweet spot, “Lean Best Idle” of the mixture/volume screw at 2 turns out. We change the idle jet size to achieve this. Naturally we cannot have any vacuum at the distributor “ported” source. This typically means that the idle speed screw is absolutely less than 1 ½ turns in “opening the throttle plate” from the completely closed position.
I know that the following jetting works at “sea level” on the 258 Jeep:
Primary Secondary
idle .75mm .60mm
main fuel 1.45mm 1.45mm
air corrector 1.70mm 1.60mm

Once on the idle circuit, ZERO vacuum at the ported vacuum source. Find the Lean Best Idle, or if you will the Sweet Spot. If more than 2 ½ turns out typically you would need a larger idle jet.
If you are out less than 1 ½ turns typically you are rich and need the next size smaller idle jet.
Like all instructions say: These “assumptions” are based on the fact that the idle speed screw is not in more than 1 ½ turns or ZERO vacuum at the ported vacuum source.

As far as the main circuit goes, the Weber 32/36 DGAV has replaceable air corrector jets. The idea here is as you go up in altitude the volume of air has lesser and lesser molecules of oxygen per cubic foot of air, so we increase the total volume of air to achieve the same amount of oxygen molecules that we had at sea level. My educated guess and experience of altitude jetting is you would need to move your 1.70mm Primary air jet to the Secondary position, removing your 1.60mm air jet. Then get a 1.80mm air jet for the Primary position. This should keep that air/fuel RATIO similar to that at sea level without removing any fuel that actually gives the bang we are looking for.
Please use this as a guide line and experiment with your setup. If not, maybe someone else on this huge post will find this useful.
UPTILLNOW

[mcmud]

An excellent post. Makes a whole lot sense to me..... When we increase the idle jet we are also increasing the "TOTAL" volume. So if "we" run a 75 or 80 idle jet and 145 main jets that is lot nearer to what you should expect to find as a good base at the lower elevations, adding in the more modest air correctors would most likely correct for this elevation with out a loss in power.

Plus... the benefits gained in haveing the ability to reach the 0"Hg reading at idle with the larger Idle Jets.

[IdahoJeeper]

UTN....another great post!!! Thank you! I'm going to run with your suggestions first. I really appreciate your explanation; you use "plain language" and very eloquently explain things. Thank you. When I purchased this rig, the PO had been trying to get it to pass UT emissions and I had no idea what they had done to the timing and/or carb.

Swatson...As I was adjusting things last weekend I looked at the linkage and had the same thought. I'm going to take a real hard look at that as things come together.

McMud...."yeah, what he said"

...and I do appreciate everyone's input....together we will get this done!!

[IdahoJeeper]

OK....here we go.

Now installed:

Idle 80 / 60
Main 145 / 147
Air 180 / 170

Mixture screw is out 2T. 1/4T in or out from there produces a stumble in the idle.

Now comes the "fun" ..... Even with the 80 primary idle jet, it will not idle at a resonable rpm without the speed screw "lifting" the throttle plate. If I tune out the vacuum at idle (by running the speed screw out), it will run but barely...about 300 rpm. If I bring the vacuum up to 5" it will idle about 500 rpm and at 8" of vacuum it idles nice at 750 rpms. I even got the timing light out to make sure that wasn't all hosed up.

Just so I understand this right.....I need to install a primary and secondary idle jet that will allow so much fuel through that it will idle at an appropriate rpm and the throttle plate will be closed and there will be 0" vacuum at the "S" port. So I guess I need to step 'em up again....

I tried UTN's suggested jetting first and met with similar results. After bumping up the primary idle jet to the 80, it got a little better.

Test drove and it runs stronger than before so I'm really pleased with the improvements so far.

Dang, I should just open an account with Redline. Here we go again.

[mcmud]

If at this point it is any consolation I think you have all the jets that you will need.

As to the throttle plate... keep it closed to the point of 0" vacuum.

The jetting changes are all over the board.

While both main jets have been increased and the A/correctors decreased its most defiantly richer. Just a note to you at this time since the emphasis should be placed on the low speed circuit first.

On the idle jets I see where you reported a 500 RPM with the 70 and a 300 RPM with the 80. I doubt there was much change with the 75 but I be incorrect to assume 400.

If you notice a decrease in rpm with a 1/4 either way while using the 80 it is likely too large or it is possible that the primary air bleed is restricted.

Before you remove it and while the mix screw is set to the lean/best point at idle... run the speed screw inward until you maintain 1850 rpm and then slowly turn the mix screw out and see if the rpm increases. Then reset it to the original position and slowly turn it in and see if the rpm increases.
-------------------
After this test and before another jet change set your initial timing to 10*BTDC at 650-700 rpm while the tube is disconnected/plugged and compare the results of idle speed at the lean/best setting along with the same tests.

[IdahoJeeper]

You got it.

I'll give that a shot tomorrow and report.