i have a 76 f350 with a 360 4bbl i know no 360 4bbl were made so theres no telling what else was tinkered on when they added this. the problem is it runs realy rough almost like its missing but its not, it shakes and vibrates alot more than my other 360 or my dads 390 my uncle is prety savy when it comes to issues liek this, he says it could be a valve or a carb issue??? any ideas i was thinking maybe a timeing issue?

 

I got this out of the latest of Mustangs Monthly so most of it applies to our Dents. I added the ignition stuff.

Possible Causes
Carb choke sticking (flooding with a rich mixture)
Idle air mixture bleed(s) plugged or out of adjustment.
Intake manifold vacuum leak - check gasket, carb spacer, vacuum hoses.
Arcing distributor cap, burned spark plug wire, or the ignition module crapping out.Check all wiring.

Diagnosis
1. Manifold vacuum should read btwn 15 and 22 inches at idle
2. Spray carb cleaner around the suspected vacuum leak area. If engine surges, congrats! You've found the leak. If engine operation dos not change - keep searching.
3. Vacuum leaks at carb/spacer base are typically due to warpage or defective gaskets. Check surfaces with a straight edge. Mill the surface to true them up.
4. Flaws in carb casting can also cause vacuum leaks.
5. Throttle shaft vacuum leak - worn shaft and bushings.
6. Vacuum leak at automatic/electric choke.
7. Manifold gasket leakage will usually cause engine oil to be draw up and cause blue or white smoke.
8. A faulty PCV valve or hose can cause an irregular vacuum leak and rough operation.
9. Ruptured vacuum modulator on an auto trans. Not only a vacuum leak but it can draw tranny fluid into the engine. Also causes smoke.

My money is on a vacuum leak cuz it sounds like the PO did a 4bbl swap.

 

I had the same problem on my 360. Turned out to be intake gasket mainly. it was leaking. Fixed that still not quite right but got alot better. Retuned carb and ran like a champ again.

 

i never thought of a vacum leak but with all the shinanigans that has been done by jack leg mechanics before i bought it i am suprised at nothing il run through your list.