I got a 75 f-250 and recently been having brake problems I did a full replacement as the rear were almost shot and front needed replaced and I tthen replaced master cylinder and power booster but after I replaced the booster it seems the engine now runs like crap. It refuses to idle and its running very rich I advances the timing and tuned the carb but to no avail. It seems no matter what I do it will not idle. I checked and rechecked all my vacume lines and ignition setup ( points coil etc) and all are fine. Anything would help I am compmetly stumped at this point. I have little experience in this field as this is my first fe 390 iv ever had the pleasure to deal with

 

The new booster appears to have a vacum leak. Unplug the vacum to the booster. If the engine idles that's the problem.

 

I tried that and it didn't help...I sprayed down all of my vacum hoses and connections with either and I even thought that it could be the carburetor gasket where is bolts to the intake but that wasent it either...I talked to a mechanic the other day and he said that if my timing chain had to much slack that could be my problem but he wasent sure. Everybody I ask seems to be stumped when I explain my problem.