carb adjustments

[westernkansas]

there sure are a lot of pages to go through to find answers to my problem. If there is already a topic about my problem please refer me to it. On my 72 390 it just smells real gassy and sometimes will diesle when turned off, stalls out at stops, and sometime it will idle real high or real rough. not sure if i should mess with the choke, or the two adjustments on the front or the screw/bolt on the choke side or the one on the linkage side, or just play with everything. Do have a carb shop in my town but he charges $75 per hour labor which is too rich for my blood and he doesn't do much car/ truck work anymore and is turning to lawn equipment work.

[westernkansas]

it is a motorcraft numbers on tag are D2TF YA
A 20 11 sounds like it is sucking a lot of air through the throttle body itself, all bolts are tight and the vacuum lines are in great shape and connected. it does backfire through the carb now and then but not all the time while trying to start. still deisels some when turned off. useing more gas then normal.

[Thunderfoot]

If it has been backfiring and running rich it sounds like you need to pull the carb off and replace the "Power Valve" on the bottom of the carb... After doing that then check the adjustments of the carb.

[Dragon]

dieseling on a car is caused by several probs. 2, mainly carbon build up in the cylinders keeping real hot, hot spots glowing and too fast an idle. The engine needs a ignition source (the carbon) and fuel (more with a fast idle). The engine doesn't run smooth as the carbon fuel mix is not firing at the same time every time the cylinder fires.

Gassy smell trash the carb or better use it as a core and take it to Checker/Kragen/AutoZone/Pep Boys and get a factory rebuilt one. My 69 F350 went from 10 on me rebuilding the original carb to 12 with a bolt on, adjust the idle mix and speed, drive off in 30 minutes.

[westernkansas]

update.......think the carb is cured. a coworker that is also into old fords told me to screw in the two screws all the way in then come out 2 1/2 turns and then adjust the idle a little, will know if it works later when i get off work.

[Dragon]

2.5 I use 1.5 and go from there

[charger01]

Let me know how it turns out for ya. I have similiar problems.

[westernkansas]

seems to be doing ok, a little bit of dieseling but not much may go in to 2 instead of the 2.5.......may even start at the 1.5. another question wich screw is the air and which one is the gas?

[Dragon]

Idle jets adjust air/Gas mix they are under the front of the carb. Idle speed is on the drivers side by the throttle linkage. big screw with a spring on it.

[westernkansas]

so what is the best setting for idle speed

[Dragon]

Auto or manual?
800 auto to start
650 on Manual

[westernkansas]

automatic so 800 rpms on startup cold engine

[Dragon]

800 warm near 1250 to 2000 cold on choke

[willowbilly3]

Run on or dieseling is almost always caused by too high of idle speed. Know the engineering deficiencies of the choke system I would suspect you have a lazy choke, in addition to the power valve problem.
This is one of the easiest carbs ever to rebuild so don't be intimidated by it. There is plenty of good knowledge on this board to walk you through it.
BTW, the idle settings, as well as base timing, are just the baseline. I have found 800 to be a little high on some engines.

[westernkansas]

well the rebuild will have to wait this old truck is all i am down to after my two other cars bit the dust within a month of each other. but once I get enough saved up to get another vehicle i will look into rebuilding the carb.