Just put a hot air choke cover on it. Gary, you have an air tube attached (rusty pipe) that is a dual heat source choke cover, commonly called an electric assist system. Very common on emission carbs.

 

You could put a hot air cap on it, drill and tap a hole in the cap and run a hot air heating line to the cap itself. Would the vacuum signal from the choke pull off be enough to draw enough air in?

 

Bill - Are you saying there is a hot-air choke cover? Something different than what I have?

And, I knew that is an electric assist choke. But none of the trucks I've seen, inc Dad's, had the electric module hooked up. The wiring diagrams show the wires but the trucks didn't have them.

 

Your carburetor is missing the choke heat shield, Gary. It bolts to the front of the carburetor to help contain the heat to the choke cap. Since this style of choke relies on hot air to open, the shield is good to have in place. Maybe that what Bill was talking about?

If your truck was made after 1973, it should utilize the "electric assist" choke. Only one single wire is needed for the "electric assist" choke to operate. It connects to the quick-disconnect terminal on the choke cap from the "STA" terminal on the back of the alternator. This is quite ingenious as it will only be powered when the alternator is turning and key on. The choke wire is often thrown away and missing.

Keep in mind: The "electric assist" portion of the stock choke system does not work on its own like an aftermarket electric choke. In fact, it doesn't have to work at all in order for the hot air choke to be effective. It is only there to "assist" the hot air choke in temperatures above 60 degrees, where it helps the choke come off sooner for cleaner emissions. It doesn't work at all when the weather is colder than 60 degrees. This part of the choke is secondary, meaning the choke will work fine without it, but the choke will not work without the thermostatic "hot air" choke system.

 

Fonzie - I think you missed my other post with the quote from the EVTM. The electric choke does work below 60 degrees.

As for the wiring to the choke, Dad's truck was pretty well stock when I got it and there was no wire. And Dad wouldn't have taken it off. Disconnected maybe, but removed isn't likely.

 

A pure hot air choke cover will not have the electrical part, just the thermostatic spring inside. There is no module, only some 351 HO engines used that and it was on the Holley 4180 that had no hot air provision.

Lariat or Fonzie, the electric assist chokes only had a metal plate on the front side of the choke area, probably to protect the linkage.

 

I didn't miss your post, Gary. The EVTM you posted is correct for the 12-volt all-electric Choke Heater. But the Motorcraft 2150 carburetor uses an electric assist choke heater, and it is calibrated to run on 7 - 9 volts.

The "electric assist" chokes do not work under 60 degrees! And that is why you also need to have the "hot air" choke in place and working for the choke system to work correctly.

If it was built after 1973, Dad's truck would have came from Ford with a thermostatic "hot air" choke with a functioning "electric assist" style electric choke. Autolite 2100 and Motorcraft 2150 carburetors built before 1973 used a simple thermostatic choke cap. Ford wouldn't have installed an "electric assist" style choke cap if it wasn't going to be used. Either your Dad's carburetor has the incorrect choke cap, or the wire from the "electric assist" choke cap is simply missing.

Perhaps, but I think it was also there to shield the choke cap to keep it from cooling off from the cooler air coming from the front of the engine.

 

I looked at the choke today and it clearly says "14V". This is the original carb on the 1981 351M. There is no wire nor has there been to that choke.

Having said that, let's change the subject. Let's agree to disagree and leave it at that.

 

Gary, the Motorcraft carburetor in the picture you posted clearly shows an "electric assist" choke cap. You can plainly see the terminal on the side of it. Per government emissions regulations at that time, a 351M motor in 1981 would have had a Motorcraft 2V carburetor with a thermostatic "hot air" choke with electric assist. A wire SHOULD be there to power it.

I don't understand why you feel so strongly that..."there is no wire nor has there been to that choke" when you are dealing with a thirty-three year old vehicle that wasn't even always in your possession. Is it really so unbelievable to imagine that after all those years, the wire simply went missing? It could have been a simple alternator replacement, or a carburetor rebuild. The wire would have to be removed to do these things, and one could easily forget to replace it.

Like you, I am also driving an old vehicle that used to belong to my Dad. Among MANY other items, it was also missing the choke wire when I took possession of it.

 

I found a Hot Rod test of the carbs we've been talking about - all 750 CFM. Pretty good read.

But here are some screen shots of the findings. First is average HP after tuning the carbs. Note that the spread is very, very tight:



Then comes the Brake Specific Fuel Consumption, which is the measure of how much fuel is used to make a unit of power, and lower is better. They said "Peak" is typically at the torque peak and "Average" is across the entire operating range.

 

Unfortunately they didn't have a Holley 4609 for comparison.

 

Bill - You said the 4609 has "mushroom" boosters? How do they differ from the straight-leg, drop-leg, and annular ones? Advantages and disadvantages? And you think a 4609 would be even better in BSFC than a 3310?

 

The primary boosters have a "skirt" reducing the air flow and increasing the velocity. Primary air flow on a 3310 is 390 cfm, on the 4609 it is 345 cfm. Throttle response is much better unless you have something well over 400 ci with good heads and cam, like a 427 rectangular port Chevy or a 429 SCJ.

I will get you some pictures top and bottom later.

 

I would love to see some pics.

Here's another excerpt from the Hot Rod test:That would seem to suggest that setting up a carb with annular boosters for max economy might be tricky. Since my cruise RPM is going to be 2000 RPM or less with the ZF5, that would be the "very bottom end" of the RPM range. So if jetted to be 15:1 at that point for economy then it would lean out even more for mid-range RPM and that could be a problem.

Wow! I didn't realize how complex just the design of the booster is and how that effects the air/fuel curve. I guess I assumed that all boosters would have the same curve and it just a matter of raising or lowering the curve to get the carb dialed in. Looks like more reading is needed.....

 

Now you know why the manufacturers went to EFI, you can change the curve and advance as needed.

Here are the pictures of the boosters. Note the the secondary ones are asymmetric and different side to side. This is due to the slight mixture variation on the FE engine iron manifold (think Edelbrock Sidewinder).