Mechanical six pack idle circuits

[68 HEMI GTS]

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

This will be where the idle circuit passes through to the base plate

Origional weep holes. I plugged these with brass tube and epoxy to kill them.

 

[68 HEMI GTS]

Time to fire up the drill

As you can see this just needs touched up with a hand drill

These will need to be hand drilled, this is your new idle fuel supply. Steady hand and take your time.

 

[68 HEMI GTS]

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.

Will relocate to here

These blocks have extra emulsion, don’t need that so I plugged the middle.

Ready for assembly

 

[68 HEMI GTS]

Still unable to obtain my desired A/F target I pulled the carbs back down and added adjutable idle bleeds to all 3 carbs

Set screws installed, you can drill and swap blanks till you get what you need.

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.

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.

 

[jos51700]

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

DAMN that car sounds good

 

[68 HEMI GTS]

I still shouldn’t have to take any crap off mildly modded hell cats either, unless it’s from a high speed roll.

 

[Jadaharabi]

Do you still have the same setup? How has it held up?

 

[67Dart273]

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

 

[68 HEMI GTS]

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.

 

[67Dart273]

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

 

[68 HEMI GTS]

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.

 

[67Dart273]

Thanks. I've never screwed with these "in the day."

 

[68 HEMI GTS]

Just in case anyone was wondering these carbs aren’t worth a ****…

 

[polyjohn]

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

 

[68 HEMI GTS]

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

Complete build

roadrunner 8.4

 

[68 HEMI GTS]

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.