i just put a holley 600cfm vacume secondary and it runs good when its fully warm. when its cold it will hesitate off idle mostly and when you accelerate when your under 1500rpms. would this be from running too lean? i had a edelbrock on it not long ago and it did the same thing when it was too lean.

 

set the choke when the motor is cold.

 

its not the choke, it runs like that for about 15-20minuites and it does it a little even when its totaly warm, long after the choke is off. i've tried it anyways and it runs like crap with the choke realy rich and dosn't stop it either. i put in some 70 jets in place of the 65s and its better when its warm but i'l have to see what it does when its cold.

 

any bog when the car is cold and you have a holley is perfectly normal. but once it warms up it should not be that way. I would have to say that your accelarator pump is not ajusted properly and you need to check it out. If you bought it used then there is a chance that the accelarator pump cam is not ment to be used with the setup that you are running.What ever it may be. also check to se what size squirters you have are not to big. you should have a 25.

 

cold air and/or cold engine will need a little more fuel on throttle opening. Give it a little more acellerator pump shot.

 

70's on a 600cfm what i hope you have a 400 sb other wise that is way to big need to go back down.

 

i guess 70s are a little big and its not the way i should solve the problem. what size jets would you recomend? should i go smaller than 65?

BTW, its a 283 right now, a 350 is going in soon though.

 

Electric choke, I presume. Set it more toward the rich direction so it doesn't come off as soon.

Since you said it does it a little even when warm, you probably need a higher number power valve. Could also be the open element air cleaner which I assume you're using. The factory put thermovac systems on the air cleaner snorkel to eliminate that off-idle stumble and still keep the engine clean enough for emissions purposes.

 

thx, i guess i'l turn the choke up some, put the 65s back in and put a 180 stat in(got a 160 now). my vacume at 1000 with no load is 18 inches, what powervalve should i use? is the powervalve the round thing with a spring in it between the jets?(sorry if i sound like a dumba$$ but this is my 1st holley)

 

dam 283 v8 thats an old motor man. how did you end up having that in your thirdgen.

your pv just opens at a sertian amount of vacum but it does not control the amount of fuel flow. Thats what your jets are for. depending on year and model of the carb you have you should run ehter a 65 wich opens at about 2 1/2 lbs of vacum or if its a really old model you should just get a 2.5 pv. you will know when you look at the pv wich is on the metter block and look for some # that are writen on it? but if you have the carb on the car then make sure that your ap is adjusted properly befor messing with the pv. you should have a 30cc ap it is not verry common for anybody to need a 50cc pump. if its a 50cc then that would explain your problem way to much fuel for a lil 283. but most likely it's just not adjusted right. when it is adjusted right you should be able to see gas come out of the squirters as soon as you tuch the throttle make sure thier is no play.