Cleaning up the idle.

What do we need to do to clean up the idle & get the "hunting" out on a BBC.
What actually causes the hunting? Thanks guys.

 

start by turning up the idle RPM a little, see if that does it

 

Fatten up the barrel a little. The reason it does it is it goes lean, the rpm goes up, the pump spins faster, it gets more fuel, the idle goes down, vicious circle...

 

idle

I found just raising the idle fixes it. We run a real lean barrel valve with a convertor. We always check the idle with it in gear when changing the tuneup because it's a fine line when it starts surging.Pain in the a$$ for the driver to stage.

 

lean the barrel valve out a little one flat at a time is one way set the butterflies a little wider thus raising the rpm a little should get you there

 

follow Jim's way it is the correct way to do it..also Jim if you read this have you done any racing to speak of this year??? money is very tight out here in the midwest plus all the rule changes..im parked for awile..Dave

 

dave i have a new look 47 fiat big rear wing and cool nose piece with carnards and every thing is a fresh as it can get with what i have but no i havent run it yet had some offers to go to the east coast area but it didnt pay enough to make the trip like you said money has been tight i cant afford to go and loose money i need to make a little so i can a least pay for the fuel to get there and back give me a call

 

Jim, what do you set your idle popett pressure to? I was told that setting it higher helps with the hunting as well. Do you set your throttle blades with feeler gauges or do you set it with the engine running. What %age leakdown do you give the barrel valve?
Thanks for the help.

 

I set my b/v to about 80%, and my butterflies to about .015. I have two quarter turn valves in my hat that i can use to lean it out with if it starts to roll/hunt. they also help with start up and warm up.

 

alot of people set there popit at 6 or so myself I set mine at 12# at idel it runs a bit cooler till we stage the car then it is out of the circut I leak around 75 to 78% blades 8 to 10 thou. car never hunts Dave

 

Set your barrel valve to 80-84%

what hat do you have? Depending on size, set butterflies with feeler gauge to about 12 thou

what is port poppet set to? Is this set to a diff pressure to idle one? Otherwise they will flutter between the two

 

i set the butterflies 8-12* barrel valve 80% idle poppet 12lbs i mine idles @2500rpms

 

jim we are on the same page..2200 to 2500 idle

 

My ole buddy jimmy rector has taught me many things

 

Thanks guys for all the help . We'll have a bit of a play with whats been mentioned.

 

idle

I set the BV 69% and adjust the blades running to 2200-2500. 14-71 superman with a quadstar hat. Keeps the oil clean too.

 

My stuff is for tractorpulling and its BBC, HH8's making 1600-1700 HP. I try and keep mine lean so the oil doesn't get so much alky in it. We are in the high 60's for leakdowns, they don't hunt/lope and we run more like 1500-1800 RPM.

 

We have a bird on a 1471, 520ci in a circuit boat. Off memory I think we set the blades around .008"- .010". Idle poppet is around 4lbs with the ports at 18-20lbs. BV leak around 75%.
I think I'll try more idle pressure & maybe less leakdown.We try to not have a high idle in the boat.