Car has been progressively getting worse.
the problem is off idle stumble. I have to date pulled carbs cleaned out everything.
Rechecked and slightly adjusted floats 10mm.
Tweaked on accelerator pump linkage (no change).
Went down idle jet made it worse 53 to 50.
Went up to 55 idle now it sort of covers up the problem but still stumbles.
Checked timing Mallory dizzy. bumped it up about a degree (slightly bettter) but still stumbles.

2.0L 86b cam Tangerine 40 IDF's 32mm vents.

Runs like a scaulded dog on main jets.

Also spent 1/2 hour synching up carb linkage (perfect) off idle. still stumbles.

So I am out of tricks. What am I missing.
Oh yea valves are set good too. good plug wires good plugs.

You gots MSD?

Had a Mallory Hyfire but that took a shit 6 months ago. Running the Mallory Dizzy with Mallory Pro E coil and inline Resistor.

Hmmm Might just put a Bosch Blue coil on it and see what it does. Good call.

Do you have a hole in your butterfly? Sometimes that hole needs to be blocked. I had a 69 Bus that required that hole to be blocked, it drove me crazy. I'll dig up a reference on it.

No hole in Throttle plates.
However The symptoms lead toward clogging progression ports.
Got half a mind to do whole sale swap on the carbs. If it is still stumbling then there could be sumpin wrong internally to the engine.
Hmm imagine that. probably 60,000 miles on this engine and ain't none of them easy.

Didja check the air bypass system? How many turns out from the bottom are those air-bypass needle screws? My webers need almost 3 full turns out from the bottom or I get loading up (too rich) coming off idle. Do you get a puff (or more) of black smoke when you throttle up? I generally get better response with a slightly rich mixture, but I think gas was condensing on the insides of the manifold if I let it idle for very long without adding more air with those by-pass screws. Another possibility is that the accel pump is dribbling fuel into on of the carbs. Make sure the lever arm and actuating cam are free to move easily. On the lever arm there is a little metal wheel that follows the ramp to make the accel pump go and on mine, the wheel was gumed up on its axle thing and wouldn't clear all the way off the cam ramp. Good luck!

Yea, I have the air by-pass screws closed as advised by many a carb junkie here.
Carbs are new style with spring loaded reach rod. no cam wheel.
no visible dribbling from nozzles

going leaner on jets made it worse so I went the other way Bigger. 55 idle jet now.


Could it be new gas blends are raising hell here? no idea what's in the rat piss down here but they sure are proud of it.

heh I know the feeling.

My car runs different on EVERY fill up.


M

could be a intake leak. A small one at that. especially since going to a larger jet helped.

You might also be lean on your idle mixture strength. Richen it up and see if it goes away.

Andys

Hmm, time to stop by NAPA for some gasket material. I think you are on to something.

Hell I'm >< close to pulling the engine for a tear down.

When I got my car (pre internet), the PO had put in the cam and Weber 40"s. I did points, plugs... ...etc, but it still ran a bit rough, coughing, bogging, misfire ... I called several of the Weber distributors to get recommendations on where to start. Every one recommended that I start by installing a multi-spark CD box to the ignition. I started with just a Pertronix (yeah, I know, but I've been running it for 10 years), which helped a bit. About a month and a half later I put in a Crane HI-6, PS-91 coil, and opened the plugs to 0.045". MAJOR improvement. Still had to play around with jet sizes a bit, but the ignition upgrade was the biggest factor
HTH
Harvey

Aaron.. What gap are you running on your plugs with the Mallory Pro E coil? 50,000 volts should not have a problem jumping .045 gap. Right?

hey joe...

i get a lean stumble on transition still... so i am in the same boat ....

i have .050 iirc with the hyfire and big coil... ALSO running cooler NGK b7es plugs

clears the plugs nicely

12/28 timing...

whats your initial advance?

Try adding a little air Joe. The CBs weber bible says "3 to 4 turns out". Worked for me.

I'd replace the accelerator pump diaphragms. at 5 bucks a pop it's a cheap fix if that's the problem.

yes, sometimes i'm a parts swapper. =-)

good luck.

I've had lean stumble but have banished it from my engine room.
.....this is on 3 hole Webers but....air & fuel are the same on a 4 pooper.

In a phrase....ya gotta run rich, ya sumofabitch.

I'm not buying that crap. The car used to freaking light the hoosiers up right off of idle. Now I can't spin skinny little crappy streets unless I dump the clutch at 3,000 RPM. This is going to require some bigger investigation. I got my path set in front of me. Now I just need to follow it and find the cause.
Plugged and idle jet going to lunch so this all just may be a wad of sumpin left over from a gremlin party.

Accel jets squirt good and consistantly.

Joe,

The foundation for any carb adjustments is proper engine timing. Usually carb's don't go out of adjustment unless it's dirt or mechanical issues. In order:

Check engine timing?
Fuel pressure?
Carbs sync?
Idle mixture?



Dave H

Thanks Dave,
I get the Idea .... Back to basics. which means go through all the stuff I thought I did right last night in the dark driveway with a flash light.

What kind of throttle linkage are you running? Cross bar? You might also try changing the ignition curve a little. Bring your max timing in sooner.

That's odd needing it to be richer in the summer. If it is progressively getting worse something might be failing. Like the pump diaphragm. You coming to Houston for the SCCA regional?

Ah......new info. I thought you were talkin about a transition stumble...now it's lack of power down low. How much flogging time you got on that motor? Check the compression lately? Mine isn't as "crisp" as it was 3-4 years ago either.

Ok, I'm on a lead now. Sprayed some starting fluid around the intake gaskets. Yup it changed tune. Whoo Hoo! I think I figured it out. Or I am hopin for something easy.
This makes the most sense considering the history over the winter ran great with a 52 ish idle jet.
Now it's getting hot and upping the jets to 55 made the stumble sorta disappear but blows black smoke and makes for a sooty pipe.
So the theory is I'm covering up a problem going richer. Not quite as powerfull by the butt Dyno either. till the mains kick in and then it hauls gud.
Yea I am finicky and demanding. I want a drag racer launch through the start light I want smooth power that pulls HARD out of a corner in 3rd gear and accelerates to 6500 RPM. Right NOW!
Used to and I think it will again.

I was using CB hex bar but came across a billet pivot that mounts to the case. Seems to have like zero slop and no deflection. seems to keep the carbs even through the whole range of throttle position.

Ok Joe,

After you check out the things I told you, (fuel pressure???) check for air leaks as lean conditions will cause the engine to run hotter. I had low fuel pressure at one time and my car ran hotter. A major percentage of your engine's fuel delivery comes from the idle jets and transition circuits. So, your idle jets and mixture is very important.

Of course, bad manifold gaskets cause air leaks too...

The CB linkage is bulletproof, I have it on my car too.

Dave H

I just love bringing a problem to the board. Thanks ya'll you have been most helpfull in me getting my head screwed on straight.

BTW CB linkage sucks. How do you keep the carbs synched through the whole range of motion? If it came out the box and you sintalled it and the arms are perfect you should go play the lottery more.

I have not seen one yet that is even close. 5 cars.
this enginemounted pivot deal makes more sense and is MUCH closer in keeping carbs actuating at the same rate.

Got caught up in other stuff last night so I will cut new gaskets tonight.

SOOO phenolic spacer or not ??????