You never answered my question about of you had a idle solenoid on that carb !

Now:
According to the info you posted about the truck I may have found your problem.

The application chart states a 14 BTDC timing setting with a choke setting of 3 rich.

Look under calibration code 7-72-R11 in the 351M part of the charts on this page of mine.
This code is for your truck.

http://mil1ion.clubfte.com/78Calibra...e-upSpecs.html.

 

It also sounds like the mixture screws on the bottom of tha carb are in too far causing a lean idle.

 

While timming is very importiant Im not so sure that, in this case, its the root. Get it close and if the probs are still there take a sec for some stupid questions? Might be a simple problem.
Have you actually hooked up a vac gauge to the intake man? If so what does it say?
Is all the smog hooked up?
Does it run better when cold?
Or
Does it do the same thing warm or cold?
At idol does the exaust smell sweet or does it make your eyes burn?

 

Sorry, I should have posted this first.

Before setting the timing, are you disconnecting the vac line to the dist and plugging the carb port?

After timing and reconnecting the vac line does the engine run bad?

 

Wow. thanks for all of the input. No, I cannot find an idle solenoid. Yes, the mixture screws are too far in. (Granddad used to rebuild Carters...says to set the screws and bring them out 1 1/4 turns then adjust...apparently, this doesn't apply to Motorcraft carb...). No, I don't have a vacuum gauge. I don't see any smog pump or related vacuum lines...Same idle issue hot or cold. Exhaust doesn't smell sweet or make my eyes burn. Yes, I removed the vacuum advance from the distributer before setting timing. And no, it had the opposite effect. I knew that when I removed the vacuum advance, the truck would struggle. As I lowered (?) the timing to 8 btdc, the idle got rougher and rougher...truck was barely running. When I reconnected the vacuum advance, the engine ran much nicer.

The idle is sounding decent, but I still have to keep it jacked up to prevent stalling in gear.

 

Does your truck have a catalytic converter?

You will need to verify the catalytic is not plugged and you have proper exhaust flow and that the exhaust flow is not restricted.

Have you checked the fuel filter? How clean is the diode on the spark plugs?

When is the last time you gave the engine a major tune up?

 

Man lets find this minor prob before you distroy your trans...

No smog?

Do you have thermal/vac switches? (Colored plug things on the intake man that go into the water jacket, with 2 or more vac lines hooked to the top)
Do you have a functioning EGR valve?

On a stock distributor the timing is set with the vac advance line removed and the port on the carb plugged. Before reconnecting vac you should have a good running engine. After timing and at idle, you should notice little or no diff when vac is reconnected.

My guess………and its only a guess.

If there is a dramatic engine change you may have the vac advan line to the incorrect port on the carb and the engine adjusted to run anyway.

Sorry this would be a lot easer if I could be workin’ on the motor rather than this stupid keyboard.

Whatever it is, I bet its simple.

 

I'm so pleasantly surprised at all of the help guys. Much appreciated. 1975ford- I dunno if I have a cat on it or not...I'll look tonite. Haven't checked the fuel filter as it doesn't seem to be a power cut out, but for five bucks, I can put one in. I haven't checked the spark plugs yet. I just bought this truck 03 April and am planning a trip in July when I'll need it. Right now, I pretty much drive it to the parts store and back, as well as various test drives. So far I've done the brakes which were screaming, and the power booster which was leaking. As I mentioned earlier, I did go buy a timing light to set the ignition timing last weekend. Previous owner had done the power steering box, alternator, plugs, wires, cap, and rotor. As I can see that the cap and wires are new and beautiful, I haven't bothered to check the plugs, but I certainly can.

Craig-yes, I have an EGR valve and it looks to be hooked up properly. How do I know if it's working? I will check for thermal/vac switches this evening. When I set the timing, I unplugged the vacuum line from the distributor and plugged the line to the carb with a torx driver. Seemed tight enough to me...with that port on the carb wide open, the truck stalls so I believe that I had a good seal plugging that port. As for being the wrong port, I really don't know. It's the only port facing the distributor...a little north and east of the mixture screw. Don't you dare apologize, I appreciate all of the help. I'll play with it some more tonight.

 

If your idle speed is correct and your are connected to the proper place on the carb (ported vacuum) then when you plug back up the vacuum advance the timing should not change. The vacuum source for the vacuum advance does not have vacuum at normal idle. What was your idle speed after setting the timing with the vacuum advance disconnected?

I wonder if your harmonic balancer has slipped. If so, then the timing marks are not at the correct location. You can check this by putting #1 on TDC...check with a wooden dowel down the spark plug hole...the TDC mark of the balancer should be right on. If it has slipped then you need to remark it to be able to time it properly.

I would get a vacuum gauge. It will help you to verify timing, engine vacuum, and should be used to set the carb.

Is this engine stock? I just want to make sure it doesn't have a wild cam in it as that would be screwing up all the good advice being posted.

Good Luck!

Tracy

 

The reason I asked about the smog was to find out how much, if any has been removed. Hooked up wrong or defective smog parts can cause similar probs but I wouldn’t worry about that now.

Timing and advance need to be corrected before you can explore for any additional probs. It is necessary that you have no vac leaks to continue, look good or this wont work. Pay attention to the vac tree behind the carb and make sure all the ports are used or plugged. Feel around here, as some will be hidden. pinching lines to see if running gets better. A vac guage is a valuable tool.

If you have a single diaphragm vac advance (one vac line), it should go to the venture vac port on the carb. If, at idle you have strong vac at the port you are using, you are probably incorrectly hooked to manifold vac. Look close and you will find another port on the carb, it should have a little black rubber cap and at idle it should have little or no vac.

Time the engine as advised above, and with vac line still disconnected and ports plugged (spend .50 and get the rubber caps), adjust mixture and idle until she runs well. Now plug the vac line to the venture vac port. Little should change. With your light connected, accelerate and you should see the timing mark advance.

One more question, Have you had the top off of the carb?

Got to go.........

 

No, I haven't taken the top off of the carb. I believe I'm working on the stock 351m. I'm absolutely certain that at least some of the vacuum lines are incorrectly installed. (Had a check valve on the way to the modulator...) I've got a few vacuum schematics that do match eachother but are a little difficult to translate into english. (I know what a vcv is, but there are other abreviations that I'm not so sure of...) I'm thinking I'll need to trace and research each of them to get this set up right.

I do have very strong vacuum at idle on that port, so either I'm hooked to the wrong port, or something is very wrong. (It's a Motorcraft carb #2100 or 2150...no id tag).

God, I love it! It's been a while since I've gotten to play with an old Ford!

 

to find the proper port on the carb, it will be one thats above the throttle plate....but honestly any port should work well enought to get a smooth idle...my 460 used to run just fine on a manifold vacuum, my friend runs his on manifold vacuum without problems and has gobs of power...but the ported line is the one you want...you said that the closer you got the timing to where you wanted it the worse it ran, then you where going the wrong direction, turn that dizzy until you get the best idle you can and see what the timing set-up is, my 351m calls for 12* BTDC at 650 rpms....if timing it to 8 made it worse then you definitely need to go the other way with it, cause even without vacuum advance you should get a smooth idle, you should even be able to drive without vacuum advance with just a slight hesitation on takeoff before the mechanical advance takes over, cause after about 1500 RPMs the vacuum advance isnt doing anything anymore its all in the mechanical advance....

 

Quote:
Yes, I removed the vacuum advance from the distributer before setting timing.

But did you PLUG that hose with a golf tee or something after you removed it ?

I didn't real the replies after this quote.So if it was mentioned ...pardon me

 

How many miles on this engine.

Just because the timing light says 8* or 12* doesn't mean it really is.
Once the timing chain and gears are stripped or wornout the timing changes.

You may have it set at 8* but it could be higher or lower.

I would do a timing gear to chain slop test to verify the Timing gears/chain aren't wornout before doing anything else.


This emission diagram should be close enough for your application.


http://www.clubfte.com/users/mil1ion/7_72J_R11.jpg

 

Tcbofade, this sounds like you have the vacuum advance hooked up to manifold vacuum, instead of the timed/ported vacuum these engines take.

Assuming it's a 2V 2150 carb, confirm the VA hose is connected to the carb port that's below the choke housing on the passenger side.