Weber popping question

[ENTDOC]

that is a good article but all bets are off with Deans motor as well as a stroked 427

[dlampe]

I am running really rich on the idle circuit. If I open the mixture screws, won't that make the engine run richer? If it fixes the popping would I want to go to a smaller idle jet? When the plates are closed, opening the screw should fix the popping to richen the mix. How do I lean out the off idle A/F ratio? Is that a larger idle jet holder? I am already at 120.

[PatBuckley]

I thought I remember reading that these are so easy to set up?

Yeah, right.

[dlampe]

It probably wouldn't be to bad if I had a jet kit. My thought is maybe go to a 55 or 60 idle jet. that would allow me to back out the mixture screw a full turn so maybe it wouldn't lean out when I am coasting down in RPM's with the throttle plate closed. Do you think that makes sense?

[Jac Mac]

Deane,

Dont Coast, use the blasted brakes to slow down, thats what you put those big rotors on there for.
Now in regard to your jetting, if its a 'lean' pop then go to a slightly smaller air corrector in the main circuit rather than the idle-reason being that regardless of you having closed the throttle that big cube unit of yours will actually pull the throttle blades partially open under engine braking conditions. Think about it, you cannot get that much air thru those 3 or 4 idle and transition orifices of 1mm dia each.
As Pat has mentioned that combo is going to try your patience to get setup correctly-dont make it harder for yourself by trying to make the carburettor into a brake caliper.

Have just done a quick check on your jet sizes etc, its a mile away from where I would start , will post later, gotta go earn a buck- monday morning here.

Jac Mac

[dlampe]

Thats how you are going to leave me? Come on, tell me where you would set the starting point.

[Allan A]

I had the same problem, the cause was a broken spring in the MSD distrubutor. Just one item to look at.

Allan

[Jac Mac]

Originally Posted by dlampe

Thats how you are going to leave me? Come on, tell me where you would set the starting point.

Cant stand the thought of a grown man crying

380 cu in =778.38cc per cyl . Therefore;

Idle jet.............. 70 to 75
Idle jet holder..... your 120 should be Ok given that you will be increasing jet size.

Now you get to the main circuit- You have to get real honest about which category you would put yourself in here- Hi Perf Road or Competition. In your case I would suggest that you might have to consider having two jetting setups for your car especially if you intend comp use due to the extremely strong signal that motor is going to give the carb when you start to explore the upper RPM range.

Choke size.........42mm Road-45mm Comp
Main Jet............170 Road---180 Comp
Air Corrector.............On the Road application around 200 thru 220 air- for Comp air should be smaller than main jet by around 50/60 eg 110/120 Air.
Emulsion tube.......Keep the F16 for Road but try F7 for Comp
Pump exh .........50

Finally I must remind you to be real careful particularly in regard to full power runs in the higher gears particularly with the larger air correctors you currently have installed, a hi speed leanout is very likely under these conditions with all the tears ( real ones ) that will accompany it. Those 40mm chokes on a large cube motor only increase the risk factor. I am sure it feels nice & responsive now in short bursts of acceleration, but when you really start to get serious they will cause some problems. looking at your engine specs you have a race engine- not street engine, treat and tune it accordingly; ie dont spend any more time than you have to under 3000 rpm.

Jac Mac