car run with choke on but dies when off

AMEN....take the time to adjust that carburetor for YOUR engine , when that carb was assembled they had no idea where it was going.

 

First thing I do with a brand new carb out of the box is open it up and clean it and set the floats.

 

Hey zman,it sounds like you know what your doing with carbs, but advice to take a new carb apart, clean it, set the floats,then adjust it,to someone who might not, sounds like worse advice than mine.

Although a new carb might not be adjusted for maximum performance for a built engine etc. I wouldnt think it would normaly be doing what he described straight out of the box.

 

Most likely.

 

If you think a new carb out of the box is ready to go then you are asking for it to not work. They are not. Half the time they are not right. Dirty. Floats off. They are not ready to go out of the box. If you get lucky fine, but why not do it right. If you can't handle taking a carb apart and cleaning it and setting the floats you need to either have someone who is do it, or stick with late models.

 

Wow. I can not believe a few of these answers for this guy. Some members just can not take themselves to say " I dont know".
For me its Vacuum Leak. too much air and when you close the choke you reduce the amount of air intake. Air is coming in someplace else.

 

That's my guess, too, but I'm telling you that my neighbor wasted a couple weeks this past summer chasing that and it turned out to be something specific wrong with his carburetor. (He told me what, but I don't remember.) This was a guy who worked as in vehicle maintainence for the school district for 35 years. He was convinced it had to be a vacuum leak right up until he finally gave in and replaced the carb.

Granted, that was an OLD carb not a new one, but the truck idled perfectly and you could rev it IF you held the choke mostly closed, but it would die when the choke was open regardless of whether or not it was warmed up.

And my experience with vacuum leaks is that the car runs better with the choke closed, but usually it will run with the choke open but just not idle. And they usually rev high when the choke is closed, too.

Therefore I am going to say that IF there is no major vacuum leak it IS something with the carb. I'll leave it to the carb experts to say what it is, exactly, that causes that problem.

 

i took out 1 idle screw at a time and blew air in the screw hole , idles fine now. that is on a edelbrock CD so it might work with a holly. spray wd 40 at the mating surfaces and if it disapears thats the leak
bob

 

a vacuum leak or plugged/mis-adjusted idle mixture setting will cause a lean idle mixture, both can be over come by choking.

 

Check carb jets for gas shellac build up or other debris clog.

 

vacuum leak

 

Take a small squirt bottle and drip fuel down both left and then right primary venturies at idle. If the idle smoothes out on one side then loads up (too rich) on the other you have a carb problem. You will have to experiment with the amount of fuel you squirt down the venturies by increasing the amount of fuel you squirt in them to see if both sides of the carb are balanced. Just squirt approximately the same amoount of fuel in the venturies If both sides makes it run better you have a vacuum problem. Look at your plugs. If they are all white it would indicate a vacuum problem. If 1,4,6,7 and 2,3,5,8 noticably differ in color would again be related to a carb problem and be related to the lean side of the carb. I dont recall if you mentioned if it runs ok under load. Fuel delivery (pump pressure low, plugged filter, pinched line) would be related to fuel starvation under load. Pinch off vac booster with needle nosed vice grips or vice grips with washers over the hose to verify booster is not leaking (if equipped). Did you flip the carb over and test fit the base basket to the carb before the installation, base gasket to manifold, manifold gasket to heads? Check PVC? This is not an electrical issue which would result in a miss. This is too lean.

New, used, or rebuilt Holley? I'm not a fan of commercial rebuilders. They are not (usuallly)calibrated to specific purpose.

 

Vacuum leak. The choke being closed compensates for a leak somewhere. I like the carb cleaner test, or if it'll run somewhat with the choke off or partially closed, place your hand over the top of the carb. If it smooths out and the idle picks up, you have a vacuum leak.

Bob