Weber Jetting Survey - Page 3

Rick Parker · #41 (**permalink**) 05-23-2011, 08:47 PM

Like your college roomate said..........share.

*13* · #42 (**permalink**) 05-23-2011, 09:20 PM

File removed. New survey posted later in thread

*13* · #43 (**permalink**) 05-23-2011, 09:26 PM

File removed

*13* · #44 (**permalink**) 05-23-2011, 09:31 PM

Uploaded a new Weber Jetting database later in thread. Thanks,Hyde

Gaz64 · #45 (**permalink**) 05-24-2011, 01:46 AM

That's nice you have posted that table Hyde.

But I find it hard to believe all of those cams listed have overlap larger than 110.

To me it seems that would be lobe centre angle.

*13* · #46 (**permalink**) 05-24-2011, 06:23 AM

Sorry, it should read "Lobe Seperation". My mistake. It would be cool to get a more comprehensive list of engines. If you know of anyone else with a weber fed V8 let me know & I'll add it to the list.

Rick Parker · #47 (**permalink**) 06-01-2011, 11:49 PM

How much of this is affected by base Altitude? .....I'm sure it is to some degree.
Also a roller cam with the same timing specs as a flat tappet cam will be able to use a smaller jet, because the faster valve action will cause quicker depression within the inlet tract.

*13* · #48 (**permalink**) 06-02-2011, 05:50 AM

It would be great to have all this info to put side by side.

Caprimaniac · #49 (**permalink**) 07-11-2011, 08:02 AM

Dear fellow Weber drivers.....

I went racing this weekend, and this time I really felt like converting to injection....

I had some big troubles getting the engine to drive properly; it was stumbling and clearly some of the cylinders didn't fire as or when they should.

I friend came up with a theory that the carbs were struggling to get enough fuel and that larger inlets to the float chambers were needed. We are talking needle valve & seat. I have seen little discussion of this here. And I couldn't find it in 13's great little table either.

A look through my setup show the needle & seat are 200.
As far as I can tell, these are the smallest type for the IDF's (200, 225 and 250 are listed in the partslist I have).

For IDA I find 200 and 300 + they also have an inlet ball valve whereof 16 different are listed.

Another cause for the Webers not doing the job right might be high cornering forces: We were pushing 99- 100% (ending out in the sand) going in powerdrift with Michelin racing slicks.

The engine has caused me headscratching before not doing as expected while going around the track; loosing mid- rpm out of the corner punch is not very funny!

I'd be thankful for any input on the matter.
(I'd like to add that my idle quality was not 100% with at lease 1 carb out of sync, which migth have caused some of the trouble. Anyway, the car went as a rocket in high RPM straightline; 7800 in 4. equals somewhere like 250 km/h)

By the way, it almost ended like thisRÃ¸ykfull gatebilfestival | sa.no but luckily, we did put in a new windscreen later that evening.
Rock on!

Caprimaniac · #50 (**permalink**) 07-12-2011, 12:20 AM

Just a quick update on the troubles above.

What I found after some checking was: Left side plugs: all 4 dark brow/ black on the RHS all 4 plugs were light brown/ white-ish. I have a fuel regulator splitting L/R in AN6 lines at the rear of the carbs. Could this be due to sideloads (g-forces)? Is it possible???

Gaz64 · #51 (**permalink**) 07-12-2011, 02:20 AM

Rune,

Run the smallest needle and seat that still gives maximum power.

You can get 1.75mm up to 2.5mm in 1/4mm steps.

If you are on an oval and only turning right, it may explain your richness on the left bank.

You may need to machine up some spacers to emulate a canted intake manifold, with the carbs leaning towards each other.

The main well and the discharge nozzle are line with the centre of the float bowl volume, and it would be difficult to overcome your problem any other way.

The float hinges from one side and will have more closing force on the valve with the fuel stacking up on the other side of the carb, thus giving a lower "fuel level" at the nozzle. The reverse is true for the other bank, thus one bank rich, one bank lean.

Caprimaniac · #52 (**permalink**) 07-17-2011, 05:27 AM

Very good advices, GAZ. Maybe I can set the floats on the LH side somewhat lower to overcome the problem. Tllting is possible, but alot of work...

Since my fuel- lines are figured as a T (ending at the front of each carb bank) I think that if the problem lie in the lines and the amount of fuel in the two banks, a connection at the front might do some good as well.

I looked at the Redline Weber webshop and I found the largest needle & jet for the 48 IDF available was the 200... (Although in my not- updated catalogue they are listed up to 250, as you mention, GAZ.)

Here we have a picture showing the plugs (4LH/ 4 RH). Quite consistent, or what?

*13* · #53 (**permalink**) 07-17-2011, 08:07 AM

Ok, seeking advice. I have that transition hesitation that is our common Weber battle & want to spend as little money as possible to get it right. Price of these Damn parts will keep a guy hungry.

I've gone up with the main jets & gone up with the idle jets & neither has solved it. I double checked the float level & fuel pressure @ 3psi. I've read through this thread again & as I see it I have two options #1 go down with the idle jet holders to 100 or #2 change emulsion tubes F11, F16???. What does everyone think? I'm leaning toward the jet holders but thought I'd tickle the minds of a few of you...
My setup on a 289 (294CI) is:
48IDA WEBERS
Choke 37mm
Idle fuel jet 65
Idle jet holder 120
Main fuel jet 150
Air Corrector 120
Emulsion Tube F7
Accel. Jet 50
Screws set at 3/4 turn

Snakebit · #54 (**permalink**) 07-17-2011, 10:26 AM

Caprimaniac, are you shure this is not a linkage issue and not a fuel issue? If the one bank is running lean and the other rich, I would check the linkage to see that both sides are opening at the same rate.

Hyde, try the f11 tubes. I called Jim Inglese and gave him all my specs. He set me up with the jets, airs and emulsion tubes and did not rape me on the parts. He was almost dead on. I had to lean out the idle jet holder from a 90 to 100 and richen up the main from a 160 to 165. The car runs great, no hesitation switched from f16 tubes to f11. I also changed the pump jets to 00.

*13* · #55 (**permalink**) 07-17-2011, 10:37 AM

It seems to hesitate when pulling slow through the throttle so I'm not going to mess with the pump jets just yet.
What essentially do the different emulsion tubes do, that's one thing I'm not 100% clear on yet. I read in one post that they allow the main circuit to start sooner to allow the cross over point to be overlapped?? That was my thinking on changing the E-tubes.

Caprimaniac · #56 (**permalink**) 07-19-2011, 02:00 AM

Snakebiter; yup- you are correct- I do have a R/L linkage problem as well. It might explain it all. I will look into it today, and hopefully check plugs & all before the weekend.

13; I cannot remember seeing you testing A/F ratio? It's very useful as to get the webers correct. Hesitation at either RPM can be due to too much or too little fuel. It is also possible to trace the problem by reading plugs.

Changing the pump jets (exhaust) to 00 I think is mandatory... See Eljaro's posts on this.

Gaz64 · #57 (**permalink**) 07-19-2011, 02:25 AM

Rune,

If you start experimenting with the LH float levels to get the power mixture correct, it will be lean in a straight line and give you a flat spot coming onto the main system.

Here's another idea: custom floats for all 4 carbs.

*13* · #58 (**permalink**) 07-22-2011, 06:54 AM

Quote:

Originally Posted by Caprimaniac

13; I cannot remember seeing you testing A/F ratio? It's very useful as to get the webers correct. Hesitation at either RPM can be due to too much or too little fuel. It is also possible to trace the problem by reading plugs.

Changing the pump jets (exhaust) to 00 I think is mandatory... See Eljaro's posts on this.

As of yet I have hooked the motor up to an A/F machine. Reading plugs at this point, learning the hard way

Gaz64 · #59 (**permalink**) 07-22-2011, 03:12 PM

Reading spark plugs will only give you an average indication of A/F ratio.

Lean at one end and rich at the other (or vice versa) may give a good reading.

You need a fast operating wide band O2 sensor gauge with data logging capability to pick accelerator pump accuracy (rich/lean), idle circuit/progression/main circuit overlaps etc.

Snakebit · #60 (**permalink**) 07-22-2011, 04:51 PM

My plugs looked good, light tan. But I was too lean above 3000 rpm AFR was 17. Went up 2 jet sizes to bring it down to 12.5. Reading plugs will get you close, but a dyno lets you zero in.

Take your distributor to some one with a Sun distributor machine to recurve your distributor. You want a total of 38* all in by 3000 rpm. That was a surprize too. Jim Inglese said to run 20* initial advance and 18* in the distributor for a total of 38*. Also keep the fuel pressure at 2.5 psi