78 f150 351m with recently rebuilt 2150. I'm trying to get this thing diald in it runs good but not perfect. how many turns should my idle mixture screws be turned out. they were 2-1/2 before I took the carb appart. And when I put it back together I had to turn the screws out 5-1/2 to 6 turns to get it to idle at 650-750 rpm and to get my vachume gauge to read 18psi and sometimes the vachume will drop half a psi I feel like thats more turns than it should need. So i thought I have a vachume leak some were and I did. one of the lines had a hole in it so I replaced all the lines caped off any unused holes and deleted my non working plugged up egr valve. so after all that I hooked my vachume gauge back up and it's still doing the same thing no change. what else should I be looking for thanks.

 

Maybe some thing off of here will help?

 

Sounds to me like you still have a vacuum leak, Try spraying a non flammable solvent around the base and top of carb if it speeds up theirs your leak

 

I built one of these -
There is another version that is much simpler involving a soldering iron and a pickle jar. If I had it to do over I would build it instead, although you do need to plug it in. It does work well and doesn't involve spraying fluid all over the place. Also I just used a bit of tape over the hole where he used a rubber plug.

 

cool your own smoke machine that'll work

 

i check my vacuum leaks with blowing cigar smoke into the pcv vacuum port onthe back of the carb. works good, just need to make sure the choke plate is closed tightly. alot less hassle im just not a fan of cigars lol

it can be hard to find the smoke if it is at the carb base due to smoke being able to escape out of the choke plate but you can pin point it by spending some time there.