'31 Fuel Issues - Need Help

[houseboats1]

Pictures

[CalCadGuy]

Ok friends, I have made huge progress, but need help with some diagnosis. I got the vacuum tank hooked up and pulling a vacuum. I drove the car and it kept moving quite well. Only exception every time I went up a slight to moderate grade, the car started sputtering and hesitated gutting up the garden. once at the top, it seemed to palace itself out after 1/2 a mile or so. I have taken it on three test drives and the same thing has happened each time. Thoughts?

[Chris Cummings]

Here's what we used to call in college a SWAG (short for scientific wild-*** guess).  The auxiliary air valve in your carburetor is on a pivot shaft that runs perpendicular to the direction of travel.  The valve is a flap kept in position over a circular opening by tension between a counterweight that's integral to the flap, and a spring that's attached to the adjusting screw (the round knob you see at the front of the carb).  If the adjustment is just right for level travel, it just might be that when you go uphill, the pull of gravity on the counterweight, coupled with the spring tension, tips the auxiliary air valve flap, and you suddenly have a lean mixture, just when you don't need one.

Because you describe a behavior that happens at the time you start going uphill, and not one that waits enough time for the fuel bowl to empty (or for the vacuum tank to go dry) I'm thinking more of carburetor (or perhaps timing/ignition) complicity.

I'm not putting any money on this theory, but it's an idea.

Best regards,

Chris

[CalCadGuy]

Chris, thanks for the thoughts. My wife and I drove the car to dinner locally where the top speed is maybe 35 mph. car ran great. I wanted to see what may happen when I went to get the car up to speed around 50. As soon as I got to around 45 mph, same symptoms as those that occurred going up an incline. Also, car seems to be idling on the high side. Additional thoughts? Marc

[houseboats1]

Hello Marc
Have you adjusted the mixture? You have had the carb rebuilt. Its sounds like its too lean when you put your foot on it its starving for fuel. With the idle you can adjust the idle screw, make sure the leaver on the steering wheel is back as far as it will go before adjusting your idle. Tell us how you got it to run properly??? I'm eager to know

[CalCadGuy]

I'll try to make those adjustments this afternoon. I removed the entire fuel pump and pressure regulator and replaced those with a standard fuel line. Disassembled the vacuum tank and made sure float was working. I redid all of the vacuum lines and used the vacuum sealer as you suggested. Once I did that, the system cycled. I'm hot really all that mechanical, but can figure things out with guidance from folks like you. Now I guess I get to adjust the carburetor, which I haven't done before. Wish me luck!

[Chris Cummings]

Good luck!

[CalCadGuy]

Thanks. Any additional thoughts on why the car runs well below 40 miles per hour, but the sputters and slows down above?

[Chris Cummings]

Random thoughts -

1.  Is the timing set correctly?  You have two sets of points (one for left-hand cylinders, one for the right-hand cylinders), and they have to be correctly gapped and then synchronized (as outlined in the shop manual) using a timing light and the marks on the flywheel;

2.  There's an automatic advance mechanism in the distributor and the weight must be free to move.  You probably don't want to take the distributor apart to check this, but it's a thought.

3.  Is your exhaust system open?  There's a heat control valve in the left-hand manifold.  The shop manual shows how to test or free it with a screw driver (without need to take it apart).  Is your muffler free-flowing?

Hope that helps.

Chris

[CalCadGuy]

Thanks Chris, I'll look at those things tomorrow morning.