Hey all, been reading here for a few weeks, in April I came into possession of a '77 F150 Ranger 4x4. It's a 351M with the NP435 4 spd and NP205 transfer. I'll post another thread on how I got the truck and all the cool details. Anyway, truck has the 2150 2bbl carb, and I've got a lean condition. Truck misses and stumbles badly under light throttle, under load and with no load. Plugs are very light tan in color. All vac. lines have been checked and verified, and I replaced the EGR as it was all carboned up and wouldn't close completely. The vacuum switch in the thermostat housing appears to be working correctly, opening at the right temp. I noticed, however, that the metal line from the PCV valve to the carb base, seems to fit very loosely into the carb base, to the point that if you remove the PCV valve, the movement of the metal line will cause it to fall out of the hole on the carb base. Is this the way it is supposed to be? I gotta believe that I have a vacuum leak there at the carb base/pcv union, but unless something is missing(a vacuum nipple?), I see no way to seal the union unless sealant of some sort is applied. Thoughts? I'm also assuming that I'm sucking some air thru the throttle plate shaft bushings due to wear, but I'm really interested in the PCV connection at the carb. FYI- I've rebuilt/cleaned the carb several times, this lean issue is the only thing still not right. Appreciate any insights!

Pat D.
'77 F150 4x4
'73 Dodge B300 camper
'70 AMC AMX
'67 Rambler American
'94 Nissan D21 4x4

 

The metal PVC line to Carburator base should have a 1-2 inch rubber line to seal any vacuum leaks.

 

Running the engine at idle with a vacuum gauge will tell you if you've got a vacuum leak. A vacuum gauge is a priceless tool.

 

There should be no vacuum to the EGR valve when idling and some vacuum when the engine is accelerated.
The rubber vacuum union from carburator nipple to metal line to PCV is a special vacuum rubber line, and this will cause the engine to incorrectly. The local part stores used to stock these rubber lines or maybe an aftermarket catalog.