Hemi carb tuning at idle

[dammstrate]

The Hemi in my 66 Coronet tribute is 472cu, World block, 10.5:1 compression, slightly hotter cam although I don't know the specs. Carbs are Ebrock 650s. Did 490 hp at 5600 at the rear wheels. After it's warmed and settled down it idles at about 1000-1100 rpm which seem high. Backing off the throttle stop to lower the idle makes it die almost immediately, indicates the idle mixture is off. I know how to set this on a single carb, but how to do this on a dual carb setup? Does the back carb do anything at idle? If I set the front carb, then how to set the back carb?

 

[Runcharger]

It uses the idle circuit on both carbs.

 

[snakeoil24]

The back carb sets first order a carb hat from td or harms to sunc them proprly

 

[Moparnocar]

Check for possible vacuum leaks too

 

[Fran Blacker]

The back carb sets first order a carb hat from td or harms to sunc them proprly

Nothing wrong with ordering from either one of them. I have Amozon prime so no shipping. Wish Summit, Jegs, Rock Auto and others would offer free shipping on small orders. They could have a yearly fee $50 or $75 for small order shipping. Went to Rock Auto to order non-resistor spark plugs, price with shipping was the same as buying local.

 

[dammstrate]

The back carb sets first order a carb hat from td or harms to sunc them proprly

Why would I need a carb hat, this is naturally aspirated.

 

[snakeoil24]

the carb hat sits on top and has a vacumr draw meter to measure vacume to help you set the lonkage and also detect leaks.

 

[AR67GTX]

Anyone have a picture of one of these or a link?

 

[Fran Blacker]

I'd be interested too. Was thinking a carb hat with a hole for a uni-syn.

 

[Fran Blacker]

Something like this? Think you still need a carb hat with a hole in it?
https://www.amazon.com/Latest-Rage-...ocphy=9003318&hvtargid=pla-568420224882&psc=1

 

[Moparnocar]

Something like this? Think you still need a carb hat with a hole in it?
https://www.amazon.com/Latest-Rage-...ocphy=9003318&hvtargid=pla-568420224882&psc=1

Interesting...ive never heard of these, they would of came in handy

 

[AR67GTX]

I would be interested but wonder what size carb throats it will fit? I have dual quad Holley and AFB carbs with different size throats.

 

[Fran Blacker]

Bought a Uni-Syn will buy an aluminum carb hat and make a hole to fit Uni-Syn. Plastic carb hats are cheaper but wonder about collapsing? Think the aluminum can be found for $16. Not mine.

https://www.ebay.com/itm/1517176683...R4S8_2_Gun0EgGrn94HylP5lV-BPPKuRoCkXwQAvD_BwE

https://www.amazon.com/Aluminum-Car...+hat&qid=1627320400&s=automotive&sr=1-16&th=1

 

[Dragon Slayer]

Original Hemi Carb are not in sync that way for a street motor. Rear carb is primary and opens 60% before Front secondary Carb starts to open. The progressive is set via the throttle levers built into the carbs. The linkage is adjusted between them to ensure they front carb is full open when the rear carb is. That is the only linkage adjustment.

Ideally you ensure front carb is fully closed and not contributing and then adjust the air mixture. Then idle up with front carb and off with rear and set front idle mixture. At that point go back to an idle with the rear. Many then like to raise idle on front so that it contributes about 50-100 rpm so not to lean out any cylinders.

BUT since your motor is not stock and you probably have a healthy cam, your required idle may have the blades above the idle ports with less contribution from idle mixture.