Weber Jetting Survey

[*13*]

The bracket sounds like a good idea. The outward fuel inlet manifolds are much more plentiful these days. There are a few of the others still around, though.

[Gaz64]

Originally Posted by jhirasak

Hyde,

Thanks for sending your latest jetting spreadsheet to me. Just as a point of interest, I would like to mention the jetting and other changes that I had to make to a set of brand new 48 IDA Webers (out of the box from Redline) to get them to run smoothly on my car. They are as follows:

1. Adjust each float needle height to 25 mm by sanding the needle seat gasket (found a difference of up to 1 mm between the four carbs)
2. Adjust each float height setting after normalizing needle seat height
3. Adjust each carb air flow with butterflys closed so they indicate within 1 unit of each other reading on the air flow syncro meter (the general recommendation is to twist the throttle shaft to get the two throats to read the same value. I chose to drill small holes in the butterflys to get the same reading on all of the carbs)
4. Decrease Idle Jet holder from 120 to 100 to cure off idle transition hesitation
5. Adjust idle mixture screws to 1 1/8 turns from closed (different taper on idle mixture screw than earlier Webers?)
6. Change Emulsion Tube from F7 to F11 to correct for main jet transition richness (found problem by use of wideband O2 meter)
7. Change throttle linkage from as-provided single cross link to a bell crank arrangement to correct for left bank to right bank throttle position error (with single cross link arrangement, if both bank flow the same amount at idle, they would flow significantly different at 1800 to 2000 rpms, linkage geometry problem)
8. Change accelerator pump exhaust valve from 00 (blank) to 50 to correct for fuel dripping into the cylinders after hot shutdown (problem made worse by recent addition of alcohol in pump gas)

For anyone planning to install Webers on their car, I would highly recommend that they perform the first three steps listed above [u]before[u] they ever install them on the car for the first time.

John

John,

I beg to differ on point 8.

The exhaust valve with a STEEL inlet checkball is OPEN at rest so will not allow pump well pressure to overcome the pump nozzle outlet check ball, even after hot engine shutdown.

The nylon ball exhaust valve MIGHT have your mentioned phenomenon, but more than likely the carburettor is percolating. Solving the percolation issue is usually the best way.

[jhirasak]

GAZ64,

In my case, the pump exhaust valves that were provided with my new Webers all had a 00 bleed. This is a blank or closed exhaust valve and the gas inside the pump chamber has nowhere to go except out of the pump jet and into the throat of the carb in the event that the gas was heated above the vapor pressure of the alcohol that is currently being added to pump gas. By using a bleed valve which has a .50mm opening, any slowly expanding gas inside the pump chamber is allowed to return to the float bowl instead of dripping into throat of the carb.

Additionally, I have doubled the gaskets at the base of the carbs to reduce the amount of heat transfer from the manifold to the carbs. I also took the precaution to add an electric fuel pump that I could shut off some time before stopping the car to reduce the level of gas in the carbs. Some or all of these measures now appears to have corrected the problem of raw gas dripping into my engine after hot shutdown.

John

[Gaz64]

John,

I still fail to see how fitting an exhaust valve of 00 (no bleed) causes your concern. The inlet ball is OPEN at rest, which will not allow pressure buildup within the pump chamber.

Similar to early Holley float bowls. They had a hanging steel inlet ball which seated by pump pressure. It had a .011-.013 open clearance.
The late Holley bowls have a viton rubber inlet valve AND a .010 vapor bleed back to the bowl. Without the bleed (or blocked), the pump can discharge as the engine heatsoaks.

[jhirasak]

Gday Gary,

I think that when the gas in the pump chamber starts to percolate, it provides sufficient pressure to seat the inlet check valve and, without a bleed outlet, the gas and expanding vapor bubble pushes the gas inside the pump chamber out of the jet into the throat of the carb. That is a guess on my part as what was going on. In any event, after I changed to a bleed valve with a .50mm orifice, my fuel dripping problem became a bad memory in the past.

Since you live down under, do you have alcohol added to your pump gas by mandate of the government? The justification by the authorities was that this was added to our gas to reduce emissions problems. I am not sure about the validity of their explanation regarding the reduction of emissions but I am sure that it has caused us some corrosion and driveability problems with older cars.

Cheers Mate,

John

[PaulProe]

Thanks, Hyde, for the copy of the jetting survey. A question for you and the others on the forum:

There are only 5 entries for the big block cars, mine being the sixth. Are there not more guys who have Webers on a big block? How about posting your specs so we can get a wider sampling

Paul

[Gaz64]

Originally Posted by jhirasak

Gday Gary,

I think that when the gas in the pump chamber starts to percolate, it provides sufficient pressure to seat the inlet check valve and, without a bleed outlet, the gas and expanding vapor bubble pushes the gas inside the pump chamber out of the jet into the throat of the carb. That is a guess on my part as what was going on. In any event, after I changed to a bleed valve with a .50mm orifice, my fuel dripping problem became a bad memory in the past.

Since you live down under, do you have alcohol added to your pump gas by mandate of the government? The justification by the authorities was that this was added to our gas to reduce emissions problems. I am not sure about the validity of their explanation regarding the reduction of emissions but I am sure that it has caused us some corrosion and driveability problems with older cars.

Cheers Mate,

John

Hi John,

I see your point, and if it works for you, then you must have had nylon check valves in the 00 pump exhaust valves. The nylon balls seat faster then steel.

We have had ethanol blended fuels for some time now, it's a lottery what you get now.

[*13*]

Originally Posted by PaulProe

Thanks, Hyde, for the copy of the jetting survey. A question for you and the others on the forum:

There are only 5 entries for the big block cars, mine being the sixth. Are there not more guys who have Webers on a big block? How about posting your specs so we can get a wider sampling

Paul

At the time I put this together, I requested info. What you see, is what I recieved.
What is needed is a web page where people can submit their specs & it will automatically post into a chart. I certainly don't have the resources. It may get a little more attention, though.

[65arboc]

Originally Posted by *13*

At the time I put this together, I requested info. What you see, is what I recieved.
What is needed is a web page where people can submit their specs & it will automatically post into a chart. I certainly don't have the resources. It may get a little more attention, though.

"13"

Can we resurect this thread? It would be helpful to new Weber new-be's.

Thanks,

Jim

[PDUB]

Hyde,


Is the photo of the spreadsheet in post 65 the complete database or is there a file for download somewhere?


PS, thought you were somewhere around Vergennes...


Thanks!

[65arboc]

Hi Paul,

I would like to get this discussion going again if you would like to help. I just recently added 48IDA's to my mild 289 in a FFR roadster that I used to run a Holly 570 on it. What a difference Webers make! I still don't have them tuned perfect but good enough to drive in traffic and have some real fun out on the open road.

Jim in Pa

[PDUB]

Agreed, Jim, but I am still a ways out on getting my set up. I was hoping to hear from Hyde before now, to keep a file on what success others have been having with their setups. He was once quite active here... hasn't been back since the end of July.

[zimmy]

Check with Jim Inglese. jiminglese@att.net

[65arboc]

We're looking for a discusion here on others experience with webers.

[65arboc]

Yesterday I spent some time ballancing my 48 IDA's as I was having some poping out of the driver side pipe. Part of the linkage between the left and right carbs had loosened up since I had not tightened one lock nut securely. Then I reset best idle on all carbs. I then took it on a 30 mile trip to see a friend and it ran so good I couldn't belive the difference. Having the carbs ballanced front to back and side to side is the real secret to getting your setup running great. I run 90 octane gas btw.

Jim in Pa.

Paul, if you have any questions please let me know and I will try to answer them based on my experience, but I am not an expert by any means. I have only this summers' driving time to relate to you.

[1795]

Whenever I am approached at the track by people who are interested in Webers, but have heard horror stories about how difficult it is to get them set right, I tell them that it is not that difficult, they are easy to adjust, and the most crucial piece is to have a strong and stable linkage. Linkages that are loose, or not well stabilized or use components that can be stretched are a recipe for disaster.

I had to add some further bracing to the support that comes up from the back of the head that connects the throttle arm to the arm that then connects to the linkage going down between the carbs as it would twist a little under hard acceleration and the car would not run right. Since stabilizing that support, no problems.

Jim

[65arboc]

Originally Posted by 1795

Whenever I am approached at the track by people who are interested in Webers, but have heard horror stories about how difficult it is to get them set right, I tell them that it is not that difficult, they are easy to adjust, and the most crucial piece is to have a strong and stable linkage. Linkages that are loose, or not well stabilized or use components that can be stretched are a recipe for disaster.

I had to add some further bracing to the support that comes up from the back of the head that connects the throttle arm to the arm that then connects to the linkage going down between the carbs as it would twist a little under hard acceleration and the car would not run right. Since stabilizing that support, no problems.

Jim

Hi Jim,

Very good information. This is what I would like to see here, others experience with their Webers to help new owners get their setup sorted out.

Thanks Jim for your input.

Jim in Pa

[svassh]

Not an expert myself but will share some notes that I have gathered from various internet sources and emails/calls with Jim Inglese. I am running a Redline manifold on a 347 with Weber 44 IDF carbs.

Weber 44 IDF Setup
Main jets – 145
Idle jets - .65
Emulsion Tubes – F11
Air Corrector – 175
Floats – 11mm open without ball valve being depressed

My timing is all in early before 3K RPM at 38 degrees BTDC and roughly 20 degrees initial.

1. With motor off, Disconnect linkage between carb left and right side
2. Back idle speed screws out till not touching, then turn in ½ turn on each bank
3. Set idle mixture screws to ¾ or 7/8 turn out from seated
4. Start motor
5. Synch carbs on each side using only adjustment screw on linkage between carb banks
6. Reconnect linkage between carb banks
7. Adjust linkage between banks till left and right side banks are in synch then lock down linkage
8. To set best lean mixture, for each cylinder
a. Turn idle mixture screw out 1/8 turn
i. If idle speed increases stop, if not repeat 8a till idle speed increases then stop
ii. If idle speed decreases or does not increase, turn idle mixture screw in 1/8 turn till idle decreases then back off 1/8 turn
b. Repeat for each cylinder
9. Check each spark plug condition after driving for lean or rich, adjust each cylinder as needed. 1/8 turn in on idle mixture screw if rich, 1/8 turn out if lean.
10. If you have a flat spot during transition from idle to main circuit, back each idle mixture screw out 1/8 turn.

I can tell you I spent weeks messing with different idle jets only to discover what a significant impact timing has on these setups. I have since gone to a locked out MSD Distributor at 40 degrees and control the timing curve with an MSD 6AL2 Programmable ignition box. Too much or not enough timing will cause a stumble thru the transition phase that you will swear is an idle jet problem. My car is very docile and predictable at low RPMs and all thru the transition curve to 3K RPM with light throttle and will climb thru the RPMS quickly with heavy throttle. I have found with my setup I do need to run slightly rich or I will get lean pops in the sidepipes under light acceleration and deceleration.

Some web links for helpful reference:
http://www.redlineweber.com/html/Tec...t_controls.htm
https://www.racetep.com/manufacturer...ber-carbs.html
https://www.gt40s.com/threads/weber-...youtube.32276/
http://www.timsroadster.com/html/tuning_webers.html
Ignition Timing and Webers
https://jiminglese.com/common-questions
https://jiminglese.com/weber-tech
https://www.gt40s.com/threads/weber-help-please.41056/

[65arboc]

Here are my final specs and the engine is running great like never before. Just a little rich at 1000 rpm idle.

Engine is a 289 bored .030 over
Heads are iron stock but with upgraded valve seats.
Manifold is from Redline Weber
Mild Grind Cam from Comps
Carbs are 48IDA
Choke are 37mm
Idle jet holder-120
Idle Jet-F-10-65
Air Corrector Jet-195
Main Emulsion Tube-F-7
Main Jet-180
Pump Exhaust Valve is Non Ported

Hope this helps someone else.

Jim in Pa

[priobe]

Hello All
It’s been a while since I’ve posted. I came across this website and checked it against my settings. It’s not perfect but you will never find a perfect recipe for any setup. It will be a fine tune trial and error.

I hope it helps put some one in the ballpark to get started

https://www.carbparts.eu/calc

Sorry if this was mentioned already.