Boston Driver’s Notebook 8/1/12 Part 2

1 08 2012

BDN 8/1/12   Part Two: The Repair of the Tuna

Note: this post has already been published as part of an earlier post.  I have broken a long post into three parts to honor all of us with ADHD.

Finally getting a day off, I went to my favorite auto website, http://www.slantsix.org for advice, searching for “running rough + stalling” or words to that effect.

The first thing I struck upon was the advice of “Doctor Dodge,” Doug Dutra recommending the poster clean out the needle valve in his carb, along the lines of what I had been thinking. http://en.wikipedia.org/wiki/Needle_valve

Rough Ridings
For all your TR informational needs, see http://www.theodoreroosevelt.org/

So like any good modern simian, I called up a youtube® video and watched a southern gentleman explain how to clean the jets in a Holley® 2300 2-barrel 350 cfm carburetor.

Not the video I watched, but still a pretty good one:  http://youtu.be/Ctw7Xrtytww

It was easy after all.  On top of the fuel bowl there is a large hex bolt with a large slotted set screw in the center of it.  The gag is to loosen the set screw while holding the hex bolt in place with an 11/16th box wrench.

Loosening the Set Screw

Remove the set screw, and it becomes easy to loosen the hex bolt.

The hex bolt is indexed around the needle valve by two parallel flat sides incised into the valve stem, and corresponding keyway in the specialty hex nut.  The hex nut also retains the rubber seal of the needle valve housing, kept tight by the large set screw.   Things of which I was unaware at the time.

As per the video, I removed the valve stem after taking note the depth at which it had been set, with about 3 threads showing, and the flats to the left and right of front.

Clean Needle Valve
ElFin photo

Using actual carburetor spray I sprayed out the valve and then checked it again.  The spraying flushed out a curl of rubber that had been cut out of the needle valve plunger and had indeed, likely been the culprit in the uncool runnings.

I replaced the needle valve and left the set screw off, which was a mistake, as I found out when I started the car.  “Why did I leave off the set screw, you ask?”  Don’t know.  Not sure.

That little seal under the specialized hex nut wasn’t a frivolous addition to the carb.

I had an old-timer point out that fact to me a long time ago back when Autozone had been ADAP.   I was buying a set of points for my previous red Plymouth convertible and had opened the box to take a look at them while standing in line.  A little capsule of grease was included in the points set.

“Make sure you apply that to the distributor hex nut,” he said.  “There are thirty thousand parts in your car, and every one of them is there for a reason.”

That seal under the hex nut was there for a reason: to keep gasoline from pouring onto my hot exhaust manifold like this.

Hex Nut with Set Screw Removed

I decided to bring the hose over.  A person who shall have to remain nameless came by later to criticize me for thinking a hose would do more good than harm against a gasoline fire.
“It’ll make the fire worse.  Spread it around,” said the helpful person.

Well sometimes you want a coastguard cutter, but all you have is a kelpy chunk of styrofoam.

Corndogger.com photo

I used logic and deduction to determine the incorrect direction to adjust the needle valve, and according to the way of my people, adjusted it in the wong direction.  This time gas came out the top of the carb and also flooded into the carb venturi (intake chamber where gas and air mix according to the venturi effect which results from Bernoulli’s principle.)

Sombrero Galaxy: Fun with Fluid Dynamics
Read more at wired.com

Then I went inside to watch a youtube® video in which a midwestern lady with a well-modulated voice explained the procedure for setting the float level.  When you screw the needle valve deeper into the carburetor, it allows the float to float higher in the fuel bowl before disengaging.

The midwestern lady also reminded those watching to disconnect the coil lead so that the car wouldn’t start.  That’s the procedure for those such as I with a mechanical fuel pump.

A midwestern gentleman in the same video also recommended placing a rag under the needle valve area.  Pressure in the line guarantees gasoline soakage in the general area.

I went back out to the driveway where there is draped a muddy blue towel.   I was prepared.

What Towels may Look Like
http://www.apartmenttherapy.com
For all Your Decorating Information

In accord with the video, I removed the sight plug in the side of the fuel bowl, and let the fuel level reset itself to the proper level.  Whether it remained at the proper level through a few cranks of the engine remained to be seen.

I once again set the needle valve to the factory setting, with 3 threads showing, and the flats to the gunwhales.  That is to say back to the original position as I remembered it.  In addition, I got the floor jack under the passenger side and lifted the engine compartment so it was level, by eye at least.

Top Center: Screwdriver Removes Sight Hole Plug

The factory setting had the fuel level too low.  Perhaps the carb had been manufactured on a Friday, as people were thinking about leaving for the weekend.  Or on a Monday after a rough weekend.  I raised the fuel level so it just spilled out of the sight hole when the plug was removed.  I tightened up the sight plug and the set screw, and started the car.  It started with a vengeance, and ran strong- stronger than before the crud got into the needle valve, it seemed.

We Emerge Victorious… On Occasion
ElFin photo

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