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I have a 1966 F100 i picked up last year. I am just getting around to tweaking it to be mine. I runs but has a stalling issue and idle. The previous owner said he rebuilt the carb. I just had it at a local 50's shop for disc brakes installed and also asked he to look at the way it is running. So he said the carb was dirty and he cleaned it and readjusted the idle. however he also said it i idle it any slower it will be stalling once again. He mentioned I may need a new carb. The one that is on the truck is a motorcraft 6R 3507 B (stamped on the carb) it is a 240 6cylinder engine. I would just buy a new one if needed since apparently the rebuild the previous owner did did not help. Anyone have suggestions or experience on what they used and has the same fuel line locations etc. thanks Jeff
Assuming your 240 still has the original style Load-O-Matic distributor the Motorcraft 6R 3507 B carburetor might not be the best match for the Load-O-Matic distributor. Load-O-Matic distributors rely entirely on vacuum signals from the carburetor for timing advance, and they require a carburetor with a spark control valve to function properly. Based on discussions, the 6R 3507 B carburetor may not have this valve, which could lead to poor performance and improper timing advance.
If you're using a Load-O-Matic distributor, it's generally recommended to pair it with a carburetor specifically designed to work with its vacuum advance system. Otherwise, you might experience weak acceleration and inconsistent timing. Some people opt to swap out the Load-O-Matic distributor for a later model with vacuum AND mechanical advance to improve performance. Then you can use a carburetor without the spark control valve, too.
Thanks for the info, I will check on that distributor as it may very well be the LOM. SO it would most likey be better to swap the distributor out for the non LOM? Or should i go find the Autolite 1100 carb and swap it that way. As of now the truck dosent idle good unless it idle screw it up otherwise it stalls. SO does anyone have info on what to replace the distributor with to match the carb or is it eaiser to swap the carb to match the distributor. thanks Jeff
FYI,
I am going to the F100 truck show in Pigeon Forge this weekend so if anyone has pics or things I can look for to help run the engine better like the correct carb or ignition that would help.
You can go either way with it. I personally do not like the LOM distributors and do like a dual advance distributor instead. Even on a good day that LOM system is a terrible design.
I agree with TA455 the LOM isn't one of Fords better ideas. A 300 I6 distributor will go right in there and they are all dual advance. Be aware if you have a carburetor with a spark control valve do not hook the vacuum line on a dual advance distributor to that fitting because it won't supply the amount of vacuum needed by a dual advance distributor, they need full manifold vacuum.
Here are a few pics of my current setup on my truck. Can anyone tell me if these are compatible or does one of them need to be switched out.
Carb is a Motorcraft 6R 3507 B thanks Jeff
I'm not used to the metal identification tag on the side of your distributor. I have several around here from 1963 through 1966 and they all look roughly like this picture with the 12127 numbers and FoMoCo cast into the housing and a stamping for the Prefix and Suffix as well as the date code.
This example is a C6TF-12127-AF which corresponds to the 300 L/D 6-cylinder engine. The C6TF is the Prefix and the AF is the Suffix. The date code of 6BC is 1966 February 3rd.
If we go by what your tag seems to show it seems it also has the Prefix of C6TF and the Suffix of AC meaning C6TF-12127-AC which corresponds to a 240 6-cylinder engine. The date code looks like 5HD which would be 1965 August 4th. Fine for a 1965 or early 1966. I sort of suspect that distributor has seen a rebuilder at some point in its life so it may or may not be original to your truck.
My current hunch is that is a LOM distributor. The centrifugal weights are underneath the top breaker plate, so it takes closer inspection to see if they are in place or not.
On the carburetor I think that is a Spark Control Valve (SCV) near the fuel inlet. Silver color and looks like a Holley power valve or an Autolite Economizer Valve. It might be that it simple isn't working correctly - meaning the SCV. They do unscrew and can be replaced.
You definitely have a Load-O-Matic distributor, those springs are a dead giveaway. I don't believe the numbers on the side of the carb tells exactly what it is. I suspect it is a universal replacement for the original Autolite carb. The advance curve for that distributor is 10 degrees @ 1.20 inches of vacuum and 22 degrees at 4.90 inches of vacuum at the crank. The distributor is kinda ugly inside, but it may still work OK. When I trouble shoot that system the first thing I do is disconnect the vacuum line and set the timing to 6 degrees using a good dial back type timing light. Then reconnect the vacuum line and see what the advance is at idle. With your distributor it should be in a perfect world 28 degrees but anything up 35 degrees is OK.
If it passes that test you know the distributor is working, to check the spark control valve disconnect the vacuum line and connect a vacuum gauge to it then start the engine it should read between 4 and 5-1/2 inches of vacuum.
Try that and let us know the results.
I saw Mikes carburetor sells replacements SCV for like 10 bucks so i may replace that anyways. It sure looks old the one that is on there. I just got this truck last fall and just now have time to get to it since i retired and this is my project. New to me is the Load O Matic stuff and the SCV etc. Basic motor stuff i get but that part is new. Im going to the F100 show tomorrow and my pick up a new carb there if I find the exact replacement. Maybe one that has been cleaned and already rebuilt thanks for this help. Jeff
There are two ways to repair a problem.
Trouble shoot it, identify what is wrong and repair it.
Throw parts at it hoping one of them will fix it. Your call.
If you have a vacuum gauge it's a pretty easy test to do and might save time versus waiting for a part that possibly doesn't end up changing the situation/symptom. I mentioned it might be the SCV itself since likely not changed with a carb rebuild and it's a critical piece in the LOM system. Good to know it can go bad and is replaceable. But I'm often wrong so don't take my word for it. If you don't have a vacuum gauge I can recommend getting one. Handy for troubleshooting various things. Mine came in an older Sun brand set that included a timing light, compression tester, tach/dwell meter and remote starter switch. Nice case it all comes in, too. Sun was one of the best back in the day. But, doesn't need to be fancy to get a reading.
I was told the card was rebuilt when i bought the truck. Looking at the gaskets etc I do agree, I did check for vacuum leaks yesterday and didn't find any. I re cleaned the carburetor already once so far and it did have some crud in it. May be some more still. Still a work in progress but keep going everyday little by little. thanks for the help here guys. Jeff
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Carburetor advice
