Ok guys I have a 85 f150 300i6 carbureted and I have some pretty bad hissing along with rough idle I'm pretty positive I have a vacuum leak but I'd like to just replace all of my lines while I'm at it they don't look the best but I don't even know where to start. I hooked a vacuum gauge up and adjusted my carb awhile back and it was pulling 16 1/2 pounds I believe idk what the normal is but that's the best I can get so any input on that? My other question is if I wanted to replace all my main vacuum lines where would I even start and anyone know a good place to get em? My local auto parts stores don't have much of a variety at all. Also I was having a problem with my brakes where if I press the brake pedal down my trucks idle dies down to about 300-400 rpms and runs really rough the second I let off it goes back to about a grand now I pulled the vacuum line going to the booster and if I put my thumb over the line it does the same thing it dies down real low and runs rough. So would this be a vacuum line or you think this is the brake booster itself going bad? Sorry for bunching a lot of questions together I just really wanna figure this out. Thank you in advance for any help you guys always point me in the right direction.

 

Stsrt behind the carb and pick one and follow it out and replace,if you find a line your not sure of or its in a bad place spray some wd-40 or what ever on the connection and if your motor slow a bit well its a vacuum leak and replace. It's a pain in ther *** i know i spent the whole summer chasing vacuum lines on my 1982 f-150. The cool thing is you get an education in the process and you know your truck better and you didn't pay some mechanic who probably doesn't really know the older trucks any way and would wind up doing what you must do any way. Gatta love the old ones.