Technical Help with tuning carb

You said that the vac lines are steel , that doesn't mean they , or what they go to can't have leaks.
There may well be junk plugging the emulsion tubes , idle feed orifice or idle air bleed ... Did you soak it in carb cleaner and blow it out with compressed air ?

 

I think on a Load-a-matic system it gets a weak signal from the venturi at low speeds, then the spark valve switches it to manifold (below throttle plate) at higher speeds.

 

Fuel delivery problem.
Usually due to blockage.
Could be vacuum related.

Do what these guys suggest. First with the carb cleaner spray or starting fluid spray to track down any vacuum leaks. Cheap, quick, easy.
No luck, do the vacuum test. Good to do anyway.

But check for good fuel flow from the tank to the inlet at the carburetor. Disconnect the inlet line from the carburetor. Put the line in a container... away from ignition sources. You can even add an extra length of hose and set the container on the ground to be safe. Disconnect the coil wire so the engine won't start. Crank the engine for 5 seconds.

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If all checks out okay, you probably have a problem at the carburetor. You might be on the right track with your suspicions about the base gasket. Small carburetors tend to have bases with narrow sections that are prone to leaking, and everything has to be just right.
Good luck.

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An old hard base gasket usually won't seal.

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Unfortunately I don't have a solvent tank. I cleaned everything off with carb cleaner and shot it through all the passages I could and everything looked clear.

 

Went to the auto parts store and asked for a vacuum gauge. Guy looked at me like I had two heads. I actually had to explain that on older engines there are things called vacuum lines, he still didn't get it. Tried to sell me a compression tester. When did I lose touch with today's youth?

 

Mechanic's vacuum gauge is just a SteamPunk Scanner. OBD-0

Try FleaBay. Probably $15 delivered to your door, in a genuine blow-molded textured plastic POS case.

Once in a while a good used Snap-On or similar Tune-Up kit will show up. Compression gauge, Vacuum gauge, and timing light. Pick your poison.

 

That's pretty funny. But yeah it's going to have to be eBay Chinese sweat shop tools for that.

 

Walmart, Lowes, Advance auto parts, Harbor Freight all show them. Search for fuel pump and vacuum tester. They will read pressure and vacuum. I probably have 2 in my tool box.

 

I see no Spark Control Valve on this carburetor.

 

If you are talking about this thing, you are correct it doesn't have one. I thought it needed one too, but there is no provision for one

 

Right - but this is what people are referring with "LoadOmatic" distributor, the distributor needs two, (2) count 'em! kinds of vacuum to work correctly.

A metered venturi source, and a manifold source. There aren't any centrifugal weights or springs aka mechanical ignition advance in the LoadOmatic. Make sure that's the correct carburetor for that distributor, or it will never run right. They weren't very well loved back then.

 

Ya my wife's mustang has that on its carburetor, it's a 66. How do I tell if the distributor is loadomatic?

 

Take off the cap and rotor, take a picture of the guts, and post it.

 

Will do when I get home

 

G, you might prove that I don't know wtf I'm talking about on this particular diagnosis.
That's good! LOL
One thing's for sure... I never knew that any carburetor had a "spark control valve".

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It looks a bit like a Holley power valve, but appears on the outside of the carburetor.


It is what controls a Load-O-Matic distributor.

The trouble is, there are versions of several carburetors with, and without them. Without one, a Load-O-Matic distributor will not function properly. They have no centrifugal advance mechanism. They work on vacuum, via that valve, and springs.

Load-O-Matic distributors were terrible when they were new. Worn, they only get worse.

The solution here, should the OP have a Load-O-Matic, would be to get a modern distributor. It will seriously feel like a 30hp upgrade (because it probably is).

It certainly looks like one of the models of carburetor that interchange with one with an SCV, but does not have one.

 

Check the hole that I have circled in the second picture of my last post. See if there are threads in it.

Get some starting fluid, and spray it in that hole, when the engine is running, taking care to only get it in the hole.

If the idle goes up, your Spark Control Valve is missing!

This would be a decided vacuum leak.

If there are threads in there, and the starting fluid test works in raising the idle, buy a SCV. You only have $11.00 +shipping to lose.

https://www.carburetor-parts.com/Spark-Control-Valve_p_1166.html

 

The threads would be set in a bit.

About there.

The resolution of the picture is not good enough for me to blow it up enough to see threads, but there is a vague appearance of them.

 

Well they say a picture is worth a thousand words.
I had heard the term about the SCV on here,,,but had no idea what it was,,or where it went.
Very good pics From the op, and,,,,it does look like a Holley power valve as well
You’re a pretty sharp cookie Gimp,,,excellent commentary,,,and detailed explanations of what all it does.

The beauty of the Hamb is,,,,there are so many sharp cookies here !
I learn something new all the time ,,,,some things I know,,,,some I don’t.
That is why I usually let the smart ones comment about things that are over my head.
I just watch and read,,,,Lol.

Tommy

 

1307 heads are better than one.
Only glitch...
Snake owes all 1307 $0.25

LOL

Everybody have a good Sunday!

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Here are the requested photos of the carb and distributor. Sorry I took so long to get them. Even in retirement life has a way of keeping you busy.

It definitely does not have threads for a spark valve. I did some research and this vehicle came originally equipped with a Holley 1940, which is what it has now. But saying it came with THIS 1940 is difficult being how old it is.
Disclaimer; please disregard the embarrassing left over grease on my freshly rebuilt carb. I assure you the inside is clean, I just didn't do a great job cosmetically with the outside. Also it is wet due to condensation in the air today, it's not leaking. In fact it hasn't run long enough to leak that much since the rebuild.

I don't see anything that looks like counterweights in the distributor, but I haven't taken that plate off either.

 

That is a LOM distributor. Does it require a carburetor with a SCV? I dunno, but need to find out.

 

What is that module inside the distributor?
Almost looks electronic?
Is that what the load a matic looked like inside?
Also,,,,there are springs in there,,,I thought no weights for centrifugal advance ?

Pretty modern looking to me .

Tommy

 

The electronic module is a pertronix electronic ignition module. It replaces the points and condenser and is maintenance free, costs about $100 and totally worth it. Screws into existing holes, installs in about 10 min. The only drawback is you don't want to leave the key in run without the engine turning for more than a minute or so due to a small risk if burning out the module if it's lined up just wrong. The stuff were looking at to see if it's a load o matic is the mechanical components on the distributor below that, of which I have no clue.

 

Awesome, thanks man. Can you tell me what about it tips you off to know it's loadomatic? And should I think about replacing it with a non-loadomatic since the carb doesn't have the spark valve?

 

I will gladly pay you Tuesday for car advice today

 

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If you can find a "dual" distributor that has both centrifugal and vacuum advance that would be the way to go. Then you can use whatever carburetor you want as well.

This is where a Shop Manual is really useful, it will explain exactly what it had when it left the factory, exactly how it works, specifications, troubleshooting, repair and maintenance. It would spec what carburetor it needs if you want to retain the LoadOmatic.

I only know enough about the LoadOmatic distributors to ID them, and that they should probably be thrown away wherever they are encountered. Sorry can't be more help.