fine tuning my webers

onefastmustang · #1 (**permalink**) 06-08-2008, 11:50 AM

To search and read all of the wonderful weber postings just confuses me more so I am going to ask about my specific problem.

My Cobra has been sitting in my garage for a while during my wifes and I fight with cancer and a brain tumor. Both fights have been successful by the way and we are both healing.

Now for the car. I have the 4x2 weber IDA-48 setup on my car. The car idles great and when you open it up above 3k is great. But from 2500-3k the car stumbles a bit. I have tried the idle mixture screw and about 1 turn out from closed is the best setting so far. Is this a jetting issue? The engine is about 395 CI due to its bored and stroked. I can dig up the current jet settings if needed to make a judgment call on this.

Thanks guys.

Michael

ENTDOC · #2 (**permalink**) 06-08-2008, 12:44 PM

so it is a windsor based motor I presume? 2500 stumble is the classic weber gremlin. We need your jet sizes and E tube type as well as pump jet size. Without that info no one can help

onefastmustang · #3 (**permalink**) 06-08-2008, 01:30 PM

Quote:

Originally Posted by ENTDOC

so it is a windsor based motor I presume? 2500 stumble is the classic weber gremlin. We need your jet sizes and E tube type as well as pump jet size. Without that info no one can help

Hi

Yes it is a windsor motor. It is a 69 block I pulled from a wrecked 69 Mustang. Here is what the current setup is.

Main Venturi: 37
Aux Venturi: 3.5
Main Jet: 155
Emulsion Tube: F7
Air Corrector: 175
Idle Jet: 75F10
Idle Jet Holder: 120
Pump Jet: 50
Exhaust Valve: 000
Needle and Seat: 2.00

Thank you for all of your help.

Michael

ENTDOC · #4 (**permalink**) 06-08-2008, 03:16 PM

I would look into 40mm venturies at some point but for now I then to think your mains are too small, so I would go up to 165 and also raise you air correctors to 200 or so(they should not affect 2500 stumble but may help keep top end good. Since your problem is at the transition point you have to consider different emulsion tubes also but go with the simple and cheaper thing first. Do you have 2 or 3 progression holes? If 3, drop your idle jet to 170, if 2 stay where you are. Make sure plugs are ok and carbs are balanced. I always start with new plugs when making changes.

onefastmustang · #5 (**permalink**) 06-08-2008, 03:22 PM

Thanks.. I have new plugs in there. I will procure the other components and give it a try. I will have to look at how may progression holes I have. I beleive it is 2.

Michael

ENTDOC · #6 (**permalink**) 06-08-2008, 03:30 PM

as a side note, if the stumble is steady at those RPMs then it is not your pump jet(accellerator Pump)

dlampe · #7 (**permalink**) 06-08-2008, 05:02 PM

A 75F10 is a IDF idle jet. The IDA jets only have one hole at the bottom. The IDF jets have an air bleed in the idle jet. I could be wrong but just check your idle jet anyway. If it has an air hole, soilder it shut and try it then.

ENTDOC · #8 (**permalink**) 06-08-2008, 05:56 PM

Dean, F10 75 should be for IDAs

onefastmustang · #9 (**permalink**) 06-08-2008, 09:09 PM

I found the jets for 2.75 each. I have ordered. God I love the internet.

dlampe · #10 (**permalink**) 06-09-2008, 05:28 AM

Sorry, my mistake.

onefastmustang · #11 (**permalink**) 09-07-2008, 06:02 PM

So I have finally gotten around to messing with this.. My summer has been hell with my brain tumor and then my mom just passed away so I now I need some distraction.

I put the prescribed parts in. I have it dialed in so that the AF is 14.5-15 at idle and it runs pretty smoothly. However I still have that stutter up around 2500-3k RPM. I have an LM1 and connected it and drove for 4-5 minutes. The AF varies from 9 to 18. I would guess this depends on RPM and shifting. I suppose this might be easier if I had an RPM scale on the graph huh??

Rick Parker · #12 (**permalink**) 09-07-2008, 08:10 PM

What are the current jets & air correctors, etc after your changes? Let's help you get THIS behind you.

onefastmustang · #13 (**permalink**) 09-07-2008, 09:48 PM

Well from memory here is the info..
Main Venturi: 37
Aux Venturi: 4.5
Main Jet: 165
Emulsion Tube: F7
Air Corrector: 200
Idle Jet: 75F10
Idle Jet Holder: 120
Pump Jet: 50
Exhaust Valve: 000
Needle and Seat: 2.00

Any help is greatly appreciated.

Mike

68gt500 · #14 (**permalink**) 09-09-2008, 04:51 AM

What you are describing is a fairly typical lean spot at the point where the mains are not just picking up yet.

You need to extend the working range of the Idle/transfer circuits.

I cured it on my car by drilling the 3rd progression hole.

This is a fairly typical modification done on the IDAs for better street manners.

Using the infos I found in the internet I went ahead an drilled the additional 1mm hole. Pretty straigt forward and the effect has been great. No more stumble.

SF_SN888KE · #15 (**permalink**) 09-13-2008, 11:23 AM

Thinking about switching to Webers from Holley/Victor combo on 289/302, but concerned with the height of the Webers. Sources tell me that the Webers with stacks are about 10.5" tall and 14" tall from the deck of the block (China Wall?). Can someone tell me the actual height for the IDA set up from the block deck (level of distributor clamp) to top of the stacks?

onefastmustang · #16 (**permalink**) 09-13-2008, 11:27 AM

from the level where the distributor clamp sits to the top of mine is 12 1/4".

onefastmustang · #17 (**permalink**) 09-14-2008, 08:44 PM

Quote:

Originally Posted by Rick Parker

What are the current jets & air correctors, etc after your changes? Let's help you get THIS behind you.

Rick

Thank you for the call the other day.. I tried your ideas and after I swapped out the emulsion tubes the problem went away. I used my AF meter to get it dialed in and it runs really smooth now. thank you so much.

Michael