big cam,carb idle ?

[67 coronet]

so i have a .030 over 383 with a 590 old school purple shaft flat tappet cam in it.about 9.85 to 1 comp ratio.minor port work and larger valves in the iron head.
idle is at around 1000 rpm.carb runs fat as hell at idle(we are talking eye watering bad here)throttle transitions are all smooth as glass and runs like a raped ape at upper rpms.
i have used several diff carbs with same prob.current carb is billet proform 750 double pump with correct power valve for idle vac.
now my question,has anyone run a carb with holes drilled into the primary butterfly?if so,how big did you start with?its about the only idea i can think of to keep the carb in the idle circuit and still idle with this big *** cam.

 

[lewtot184]

try bigger idle air bleeds. thats an awful lot of cam for a lower compression 383. mopars version of the racer brown stx22, i believe, somewhere between 90-100 degrees overlap. drilling the throttle plates is used when there's too much transfer slot exposed.

 

[Meep-Meep]

X2 Lew ^^^

Me personally I'd be pulling out that cam and putting in the .528" / 284 mechanical.

 

[Gpuller]

I started with 1/8" holes in my carb. Your probably running butt load of initial timing too?

 

[mopar 3 B]

That shaft was not really meant for street use and am surprised it idles at 1000. Put bigger air bleeds in the carb.

 

[lewtot184]

X2 Lew ^^^

Me personally I'd be pulling out that cam and putting in the .528" / 284 mechanical.

this is a good choice, or maybe a comp cams 282 magnum.

 

[Moparsmitty]

Like Lew and everybody says, that's just a bad cam for that combination, especially if you are running an auto trans. Do yourself a big favor and go to a more streetable cam.

 

[mopar 3 B]

What is your idle vacuum? If this is your cam 310/310 duration 100° lobe separation and .590 lift you definitely have a kickass ride over 3500 rpm but idles like a paint shaker.

 

[Cranky]

I'm also curious to know what the initial and total timing is.....and idle vac.

 

[67 coronet]

idle vac is about 7 or so(fluctuates a bit).air bleeds are already the biggest i could find.(got from a proform main body on other carb)initial timing is 20 deg advanced with 36 total all in by 3200 rpm or so.lewtot184 hit it on the head with too much transfer slot exposed.i am getting off the idle circuit to make it idle and it gets way too rich in a hurry.thats why i figured the plate hole to get a bit more air in there and allow a lower idle screw position,covering more of the slot.motor was built with spare race parts i had lying around from several old builds.thats why the weird combo of parts.

 

[mopar 3 B]

Curious as to what transmission you are using and what rear gearing is? I ran a similar configuration over 40 years ago and have saved most of the combination for future use of some sort. Have always wondered about using a 727 but torque converters just were not a desirable option years ago.