Emulsion tube broke?

[anothersteveg]

Ok, here's a strange one. I've got a couple other threads, basically I'm working on a '77. It wasn't really running when I got it, so far I've done points, plugs, cap, rotor, checked gaps, valve lash, timing, timing belt, coil, alternator, starter, numerous wiring issues, and cleaned/replaced the gas tank and lines. Several other things, including a carb rebuild.

Car is still missing and running erratically at idle. I have followed the advice posted previously (thank Majic) and have been trying to track this down but having no luck. I just can't seem to find what appeared to be a vacuum leak. When I put my hand over the plate it ran much better. I have removed the emissions and checked every vacuum line I could find including the brake booster. Everything seems to check.

So out of pure frustration I started going through everything for a 3-4th time. The only thing I hadn't double/triple checked was one emulsion tube. I couldn't get the primary out when I rebuilt the carb. I figured no big deal, I soaked the entire section and figured that would clean it out. Blew it out, etc. The secondary came out and got cleaned.

So tonight I dug in and finally got it out. Did the coat hanger thing and after some work, it came out. Turns out it was busted in half. How in the world did that happen? I didn't pry enough to have done this. As far as I could tell the carb had not been apart in a long time.



Please tell me this is the magic bullet causing my problems?

Also, where can I get one? I haven't found anywhere with the correct number, F74 I believe?

[anothersteveg]

I guess I'm wondering why an emulsion tube would seem like a vacuum issue? I can't find any obvious vacuum leaks and spraying carb cleaner doesn't show anything. When I spray around the choke assembly it runs better, but I assumed it was just the fumes getting into the intake?

I'm going to switch them and see if that makes a difference at idle.

[manoa matt]

I probably have several extra emulsion tubes, I'll check to see if its the same F74. The emulsion tube does just that, emulsifies. It helps to mix the gas and air and is absolutely essential. If you just switch them it should improve the primary circuit, but when you open up the secondary it will start to have issues. I don't think the emulsion tubes come into play with the idle circuit, so there may be other things to check after you get a new emulsion tube.

A close up inspection of the fractured surfaces will give an indication of when the damage occurred as the brass will patina with age.

Another thing to check would be the idle jet and idle solenoid. You may have already done the test for the idle solenoid where you turn the key to the on position and touch the electrical lead to the terminal to hear the solenoid "click". However I had a carb where the tip of the brass idle jet was worn on one side. It would not fully seat, and allowed gas to bypass the jet. The carb was un-tuneable on the idle circuit.

[anothersteveg]

Thanks Matt, let me know if you have any. I found a place over in England, and possibly a guy in California. The one I pulled out is a
F73, the one from the secondary is an F7 so they appear to be correct for the year. When I put the F7 in the primary, it was better, but still not right. I didn't switch the jets and they are different, just the emulsion tube so maybe that's part of it too.

If anyone has any experience or knowledge using different emulsion tubes please let me know. I'm not sure what to do if I can't find one. Is there another size that's close? How big of a difference is there? I know it's a 61440 series of which there are many readily available sizes, just not finding an F73.

The idle solenoid checks. How did you determine that yours was not seating correctly? I'm open for any ideas at this point. It does seem to be the idle phase that is the worst. With the choke engaged or the throttle opened it runs pretty good.

I've been fighting an oil leak from the cam box gasket. I've decided to tackle that while I'm awaiting the carb parts and I've got to leave town for work so I won't be getting much done.

[majicwrench]

Don't swap the tubes, they are different.

How it broke doesn't matter at this point.

Like Matt says above, and has been said before, idle circuit on these plug often and easy. Clean idle/slow speed jet and/or idle soleniod. You cannot effectively clean the idle soleniod unless it is energized.

Keith