more 38/38 problems

[boldtu]

I took my 71' all stock but the Weber 38/38 carb with a cannon manifold. I took it over to 2002 ad and they adjusted it but it is still hesitating. I think it is the float adjustment but I have never done it before. Does anyone have a step by step an how to do it? with the gap on the floats?

thanks,

chet

[wagnerf15]

Have you sniffed around www.redlineweber.com for their tech articles? Lots of good stuff there, you might find what you're looking for.

[Guest Anonymous]

I took my 71' all stock but the Weber 38/38 carb with a cannon manifold. I took it over to 2002 ad and they adjusted it but it is still hesitating. I think it is the float adjustment but I have never done it before. Does anyone have a step by step an how to do it? with the gap on the floats?

thanks,chet

CD frequently posts pics of float drop and settings. If you can handle the 6 screws holding the top of the carb to the base and the e/c clip for the choke linkage, you ought to find it very easy to bend the float tangs with your fingers, needle nose pliers or even tweezers. It is possible that the floats have developed a leak making adjustment futile but the only realistic way to check is by removing the top and inspecting.

You mentioned using a cannon manifold but I am not aware of any significance. The cannons I have encountered have slightly smaller diameter runners than the stock BMW offerings. This should provide for better low speed operation.

[c.d.iesel]

...not so sure 'float level' is the cause for

your "hesimatations" but still important

to know what it is and it's adjusted correctly -

along with 2002 other adjustments like

dwell, point condition, distributor condition,

advance mech condition, timing setting,

compression, secondary ignition condition........

thanks and credit to the folks at Pierce Manifolds for this technical

page

FLOAT LEVEL - DGV / IDF / DCOE / DCNF / IDE-XE

The float level is a critical part of carburetor calibration. Changing the fuel level in the bowl will change the point that the main circuit starts to feed, alter the characteristics of an emulsion tube, and affect drivability and fuel consumption.

GENERAL INSTRUCTIONS: Float level, in mm, typically refers to the distance from the face of the carburetor top cover to the float. With the top cover held vertically (float pivot at the top) and the float tab (Lc) resting against, but not depressing the spring loaded ball in the needle valve, measure between the face of the carburetor top cover to the top or bottom of the float. On carburetor models where it is required to remove the float to replace the top cover gasket, the measurement should be made with the gasket in place to the gasket face.

[boldtu]

thank you for the diagrams

you may be right, I have just exhausted everything else and thought I would try that. I have had trouble with the idle. I have it cranked all the way down and it still sits at 1200-1500. I changed the fuel filter and cleaned all the ines so I know it has fule available to the pump but dont know where to go from there. I also want to do it myself, although I find myself itching at Ireland Engineerings number more and more

thanks again

chet

[finkbuilt]

I took my 71' all stock but the Weber 38/38 carb with a cannon manifold. I took it over to 2002 ad and they adjusted it but it is still hesitating. I think it is the float adjustment but I have never done it before. Does anyone have a step by step an how to do it? with the gap on the floats?

The 38/38 is notorious for causing a "stumble" as it transitions from the idle jet circuit to the main. I was never able to fix mine (with jetting and adjustments) and eventually went to 32/36, then Fuel Injection.

However, I recently hear a tip that you might try if you get desperate and have extra parts to play with:

If you back the throttle stop screw out all the way, and set your idle by actually bending the throttle plate open a tad, or drilling holes in it rather than by turning the throttle shaft, you will change the point (in engine RPMS) at which the fuel circuit transition occurs, and perhaps it will work better. perhaps not.

If your idle is as high as you say with the throttle stop screw all the way out, then I would check the throttle linkage and look for an open vacuum port or something.

Never tried this myself.

Just an idea for the desperate.

[Paul7002]

nearly so dire as you describe. but have learned that advancing the timing will increase idle speed. Perhaps you're too far advanced? Try retarding Just a tad - tiny adjustments can make a big difference. But remember to mark where you r starting from so you can get back there, or at least show the professional what you did when/if you break down and seek help.

[TobyB]

Ok, by twisting screwdrivers, you should be able to make it stall dead.

If not, look at your choke pullup, the idle screw, anything that can hold the

throttle plates open. 'Cause if it's idled up too high, you'll

lean out the idle circuit (screw) too much, and then the

transition will go lean. If you don't have a couple of turns out on the

idle screw, transition can go to pot.

Yes, do check the float level, and also make sure the needle valve seats properly.

I found that with a transition jet of 55 or 60 and a main of 135 or 140,

the transition stumble at 65mph cruise was pretty close to eliminated.

If you're having stumble elsewhere, look for other things.

Like air leaks...

hth,

t

ps, ditched the 38/38 and went back to a 32/36 when gas was stupid...

and I don't miss it enough to dig it out until track season hits again...

[Guest Anonymous]

If you back the throttle stop screw out all the way, and set your idle by actually bending the throttle plate open a tad, or drilling holes in it rather than by turning the throttle shaft, you will change the point (in engine RPMS) at which the fuel circuit transition occurs, and perhaps it will work better. perhaps not.

Had similar carburetor on 73 V6 Capri. Very tiny holes were drilled on the leading edge of the throttle plates. The holes came from the factory. Remember other carburetor cars with similar modifications including one with a throttle flap that had another spring loaded round flap that clearly opened under high manifold vacuum (probably ven de throttle was closed shut during deceleration). Think I have seen this on FI throttles too. Have assumed this had more to do with reduction of NO rather than smooth engine operation, but it may benefit both.

I would try changing plug heat ranges and/gaps (larger), rejetting, valve adjustment and timing modifications to resolve your problem. Yet, I would not rule out the addition of throttle plate bleed holes. Throttle flap holes can be reversed/fixed with a little solder.

Good luck.

[TobyB]

Had similar carburetor on 73 V6 Capri. Very tiny holes were drilled on the leading edge of the throttle plates.

I've also seen plates where the edge of the plate was thinned right at the idle/progression holes...

fun stuff.

t

[AlexB]

Thought I resurrect this thread to see if I could get some help with my 38/38.

Just installed a 38/38 + manifold I purchased from a fellow FAQ'er. Car pulls and drives excellent. Only thing is it runs great when you first start the car, but within 20 seconds of starting, it starts to idle sort of rough. Not terribly by any means, just a little shakey.

Let's assume all tuning has been done correctly. New dizzy, ball at 1400, dwell is good. Valves are lashed properly, all ignition replaced EXCEPT red coil. Opening the choke makes no difference in idle besides rpm.

I've fiddled with the two adj screws and I'm 1.5 turns out on both idling at 800 or so. This is about as good as I can get it.

Any thoughts on why the car would run perfect for 20 secs and then get choppy each time it's started?

[TobyB]

fuel pressure.

The float bowl's overfilling, and spilling fuel into the carb.

That's an idea...

t

[AlexB]

So I fiddled with it this weekend, but didn't figure it out or look into fueling as the cause.

This is what I did:

Disconnected vacuum advance from dizzy and hooked up a vacuum gauge.

Fiddled with the two mix screws until the needle was "steady" at 20 lbs vacuum.

*Car ran great, or noticeably better*

Hooked it back up to the dizzy and it starts shaking again.

Tried pinching vacuum line to see if the advance is leaking; no improvement.

Dizzy is one from NAPA.

What gives?

The car runs slightly different if:

-The vacuum advance is plugged into the carb

-The vacuum is hooked from the carb to a gauge. *by far the best*

-The vacuum is hooked from the carb and plugged.

Toby, about the fueling, the carb came off of a '74 I believe. Would putting it on a 72 screw something up? I'm still learning here

I willing to go out there and try what I can to get this thing running right.

BTW, the 38/38 is amazing on this little motor, even when the tuning is sub-par.

Thanks!

-Alex

[jgerry2002]

Dizzy is one from NAPA.

Probably your issue. Any more details? How was the timing set? Do you know if the distributor has and vacuum advance or vacuum retard on it? Who makes it? Whats the advance curve like?

[AlexB]

Dizzy is one from NAPA.

Probably your issue. Any more details? How was the timing set? Do you know if the distributor has and vacuum advance or vacuum retard on it? Who makes it? Whats the advance curve like?

The dizzy from NAPA has 0 231 115 072 on it, but has been covered with paint pen; probably some type of QA stamp.

The original dizzy was a 0 231 180 003 unit but was completely toast.

Timing was set with a timing light and the ball is steady at 1400 rpm.

I have no clue who makes the dizzy although it is clearly a rebuilt bosch unit, I have no clue what the curve is like; how would the curve effect idle?

Thanks for the help so far guys.