fine tuning webers
 

Hello all,

I am in the process of fine tuning my webers on a 427 FE motor.

I am currently running

Choke 40 mm
55 bypass bottom of boil
100 air holder
60 idle jet
210 air corrector
F7 emulsion tube
160 main jet

I have taken the car for a drive and it drives great!!!!! Transition is perfect.

The only problem I am noticing is that it is running a little too rich on the idle circuit. Which is cause a rich smell.


My question is I am looking to lean out my idle circuit. Should I

1) change idle holder to 105 , 110 , 115 and leave fuel at 60
or
2) change idle fule jet to 55 and leave holder at 100 and open mix screws to help with any popping from intake.

Also, I have read that you can increase the main jet to help with drivability issues resulting in the transition circuit.


For example:

I began my tuning with a 55 idle and a 120 air holder and my mixture was good not too lean not to rich.

air 225
F16
155 main

Drivability was poor after 2000 RPM

I made the change to 60 idle jet and slight improvement but same.

Changed air holder to 100 , again better but not perfect.

I then change main circuit to

210 air
F7
160 main

This made driving perfect but slight rich while driving.

So should I do what is listed above or bump up main jet as well.


I guess bottom line is if I bump up my air holder and richen up the main (not idle) will this help with letting to lean out stand still idle.

Thanks

I would drop the idle jets first, it is much cheaper to do than the holders. Ultimatly the holders may be the answer

Entdoc,

here is a question

After 2000 RPM, if I change the main jet (not idle jet) from 160 to 165 , 170 will that allow me to lean out my idle circuit.

If I understand the books that I read correctly, the main jet helps with the idle circuit around 2000 rpm and carries it the rest of the way.


When I tried the a lower idle jet 55 with 100 holder (prior to the making changes to my main circuit) I still experience a lean popping condition right after 2000 rpm.

However I increased the idle jet to 60 and experienced the same problem.


When I changed the air corrector, e tube and main jet car ran great. (210, F7, 160)

Now I am looking to lean out my idle and everything below 2000 rpm.

everything I have read indicates that the main circuit does not come untill 2500-2800, but if I have learned anything from working with webers it is that nothing is black and white. If you have not tried the smaller idle jet with your other changes that is still what I would do first. If you have the larger holders in hand I suppose it really does not matter what you try first. Always look at timing when making changes and play with the idle screw a bit also.

I agree nothing with webers is black and white but here is the article

"Idle jets operate from idle to 2500-3000rpms or so. Main jets are primarily from 2500-4500rpms, and Air jets affect the engine from 3500/4000 on up. "

http://www.aircooled.net/gnrlsite/re...es/jetting.htm

5th paragrah down.

It seems as if they are suggesting that the mains and the idle jets overlap. it also seems that the idle jet is at the taling end of the idle circuit at 2000 rpm and the mains need to start coming in to help the ending of the idle jet.

Could this be correct?

I do not think the main jets have much to do with what is happening at 2000. I think the E tube probably has more to do with when the transition takes place.

I have tried the 55 idle jet with the current set up

40 choke
100 idle
55 idle jet
210 air corrector
f7 tube
160 main
55 bypass

the smell of the exhaust is great, however I get popping thru the carbs and leaning condition.

I open the mix screw 1/4 turn to make it 1 3/4 and it was a little better but still needed fuel.

I replace the idle jet with the 60 and back down the screws to 1 1/2 and it runs alot better.


According to the article it suggest that you should change the main jet. I will give that a try.


According to all the books the etube should only be changed on a dyno and does not make much of a change.

If the f7 is the riches tube bottom RPM what etube are you recommending.

Is there a chart that list all the tubes from rich to lean or vice versa.

Suggestions please??/

bump......

Here's a thread from the innovate tuning forum, might be of interest, I learnt a bit more.

It's about DCOEs but the theories can apply to IDAs and IDFs, many threads in here about webers.

http://www.innovatemotorsports.com/f...ighlight=weber

read Elarjo's thread on this forum, it is very good and talks about the e tubes. chuck