Mechanical six pack idle circuits

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68 HEMI GTS

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i posted some of this over on for B bodies only but thought it may be of interest for some guys over here also as it seems a lot of the “A” body guys run the 4782 & 4783 direct connection or “hustle stuff” carbs. In my case I’m running a set on a 511 low deck with Indy SR heads and solid 260/266 @ .050 camshaft. I decided to run a 4412 “500 cfm” center instead of the anemic 4782 center. The issue I experienced was the unadjustabe outboard idle circuits just did not supply enough fuel at idle on my low vacuum big cube engine. My first “fix” is I went up .010 on the weep holes that supply the fuel. Unsatisfied with that I ended up adding full idle circuits as well as adjustable idle bleeds. While this was a bit involved, I’ve been able to really dial in the cabs to have excellent A/F readings at idle & cruise while maintains great drivability and WOT performance.

Tools needed;
Numbered drill bits
Small harbor freight drill press
Center punch
Some QFT/proform metering blocks ( I went without powervalves although you could add those too if desired).

For adjustable air bleeds
8/32 tap & 8/32 brass set screws

First step is identify where we need to add the circuits

The main body face is predrilled although it will need to be drilled slightly deeper
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This will be where the idle circuit passes through to the base plate
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Origional weep holes. I plugged these with brass tube and epoxy to kill them.
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Time to fire up the drill
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As you can see this just needs touched up with a hand drill
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These will need to be hand drilled, this is your new idle fuel supply. Steady hand and take your time.
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I went with these blocks because they were the cheapest quality block I could find


High idle feed restriction. Seems to be a topic of debate. I like to run them lower.
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Will relocate to here
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These blocks have extra emulsion, don’t need that so I plugged the middle.
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Ready for assembly
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Still unable to obtain my desired A/F target I pulled the carbs back down and added adjutable idle bleeds to all 3 carbs

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Set screws installed, you can drill and swap blanks till you get what you need.
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Once I got it where I was happy I relocated the supply line and insulated the fuel lines, I have wrap too insulate the fuel log for long drives. It just looks like crap so I’ll leave it off for local cruising.

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With some tuning and tweaking she’s right on. I would caution that if you plan on going off the deep end that you have a quality A/F meter as well as a good understanding of carburators and what you are affecting with your changes.

 
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Ohmygod, I hope she doesn't get pregnant...I just nutted

DAMN that car sounds good
 
I still shouldn’t have to take any crap off mildly modded hell cats either, unless it’s from a high speed roll. :steering:

 
How do adjustable bleeds "adjust?" I've no experience with 'em
 
How do adjustable bleeds "adjust?" I've no experience with 'em

you have 4 air bleeds on a normal 2 circuit holley. 2 outter bleeds control air to the idle/transfer circuit while the inner bleeds control air to the main circuit. You adjust them to fine tune your a/f ratio along with some other factors.
 
No I mean how do they adjust mechanically? Do they have interference fit like some rockers and you just turn them like needle valves , or do you pull them and change them like fuel jets or what? I'm 72, never screwed with 'em. No doubt you have some awesome stuff
 
No I mean how do they adjust mechanically? Do they have interference fit like some rockers and you just turn them like needle valves , or do you pull them and change them like fuel jets or what? I'm 72, never screwed with 'em. No doubt you have some awesome stuff

no, in this case I drill them different sizes with numbered drill bits and swap them out till I get what I need.
 
Wow I only just seen this and I'm very impressed indeed!
I have a 71 GTX that I'm gonna run in UK Superstocks.
It will be a 512 with a six-barrel set up.
Now I know exactly where to set my sites!
In the high tens lol:thumbsup::thumbsup::thumbsup:
 
One thing I should add to the thread as I did some intake work that really helped out the drivability and distribution on the bigger cube engine. Idle quality greatly improved. I believe it’s faster as well but I changed a few things so I can’t quantify a number.

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