Holley 1940 question - What's this tubing for?

[smsag04]

I'll start off with my introduction. My wife and I just bought a 1965 Mustang coupe for our first restoration project. I'm pretty mechanically inclined, just lacking a little experience. This is my first vehicle with a carb.

I've identified the carb as a Holley 1940. It has a Holley Reman sticker with the part number 64-5152.

There is a piece of tubing that runs from near the top of the carb to the exhaust manifold. Near where the tubing connects to the carb, there is a dial that faces the front of the car. What are this tubing and dial for? The tubing is rusted out (like in two pieces), which may be a good reason that I can't get it running right.

Also, how is this tubing connected into the exhaust manifold? It doesn't look threaded and I'm not sure how to get it out.

-Scott

 

[rmoe88]

Hello smsag04, that tubing is for the choke. Exhaust heat rising up it to a heat activated spring (that dial adjusts it) and as the spring gets hot it closes the choke butterfly. If the tube is broken in half then your choke should not be working.

 

[wallaka]

Hello smsag04, that tubing is for the choke. Exhaust heat rising up it to a heat activated spring (that dial adjusts it) and as the spring gets hot it opens the choke butterfly. If the tube is broken in half then your choke should not be working.

 

[smsag04]

Thanks, choke was my best guess. I'm guessing that the dial is to adjust how much the engine is choked.

How is the tubing connected to the exhaust manifold?

 

[JackFish]

This kit comes with some fittings:

You drill out the old hole in the manifold, and one of these gets popped in with the collar type tool you see there:

There are other similar kits, this one comes with a fitting for a header as well.
The end of the tube just sits in the fitting.

 

[james singleton]

SMSAG04, Normally there is a hole/opening in the exhaust manifold below the carb. There is also a hole/opening in the intake manifold for a vacuum line (if needed); so don't mistake the vacuum opening with the hole in the exhaust manifold. The vacuum hole in the intake is above the hole in the exhaust manifold. I don't believe the hole in the exhaust manifold is threaded; just slip the choke tube into the hole.? Anybody else???

 

[ludwig]

If you have the stock manifold and the pipe is broken off or the choke non functional, the choke pull-off may be broken or gummed up and need an R&R. The stock manifold may in all probability have the wall between the 3 & 4 siamezed outlets burned through at the wall. This means that if you hook up the stock choke intake tube, you will be sucking hot exhaust into the plastic cap, not the warm or hot air it needs. This will melt the black cap and clog the pull-off mechanism.

A better idea, even with the stock manifold is to get a little aftermarket warm air collector and pipe like I show here. It has a metal dome that clamps on the exhaust manifold. The carb pulls through a hole in the choke pull-off spring. This hot air goes up the S-shaped tube in white to the pull-off spring. But now there will be no hot exhuast gas; just hot air.
The kit I got cost 5 or 6 dollars at a speed shop. It came with the asbestos sweater as shown. I tapped and plugged the tube openings in the original header, top and bottom, because at this point the wall was burned out and they were nothing more than an exhuast leak. I installed the header later and kept the little tube thingy.

The line out of the side of the carb throat is the vacuum advance to the diz. That brass plug with black tubes sticking out of it is a manifold vacuum source. This is where I hook up my vacuum guage and tother stuff I will need, like power brakes. The large tube out the front of the vacuum block is for the transmission modulator.