Adding idle circuits to Holley DC six pack

[68 HEMI GTS]

the out of the box calibration on the dc mechanical outboards is pre-set and non adjustable. They probably work fine for most applications but were not sufficient for my large cammed, low idle vacuum 511. They struggled to provide enough fuel at idle to keep the engine happy. The addition of idle circuits will solve that problem.

These are the original weep holes. I plugged these with some brass tube and a bit of epoxy.

The main body has the idle hole pre-drilled on the face. I did have to go a bit deeper to intersect the hole I drilled on the bottom of the main body.

As you can see the hole didn’t completely intersect. A quick touch with the hand drill fixed that

 

[68 HEMI GTS]

Next the base plate needs drilled

 

[68 HEMI GTS]

A set of aftermarket blocks with idle circuits

Note original location of IFR.

And moving to here

Done

Next I will be adding adjustable idle bleeds as I have some work to do on the off idle cruise A/F ratio. Should have parts this week. Stay tuned. This mod can apply for any Holley carb that you want to add 4 corner idle too with a few minor differences.

 

[69 GTX]

Very nice!

 

[Paul_G]

Nice work.

 

[68 HEMI GTS]

Had a little time today so I added adjustable idle air bleeds. Once I could adjust those she started coming right around

Original bleeds removed

Drilled and tapped

And done

 

[68 HEMI GTS]

Been tuning on it here and there for about a month. Running real good, ready to pull the O2 meter out. Idles 14.0 on neutral, 15.0 in gear. Low speed cruise is 13.0-13.5. High speed cruise is 14.0 -14.5. I have a forsaken 8.5 high flow powervalve in it with .065 PVCR. Just to show it idles at 8” in neutral and 5” in gear and as I have stated several times the PV has no effect on the idle or low speed cruise A/F ratio. I gotta re-route the supply line to the distribution block to prevent vapor lock. Took a bit work but, was defiantly worth the effort. Runs strong at WOT but, the dominator has it for all out performance. Single plane on this big motor is a bit better as far as idle charistics. The mechanical carbs are a bit stronger than the vacuum carbs as it should be. Mechanical outboards flow a small bit more. I plan on leaving this set up on it as I have a real A12 hood and air cleaner. Mechanical carbs will be fun when I slip the 4 speed back in.i guess if it was easy everyone would do it..

 

[biomedtechguy]

Watched and commented on YouTube.
Your knowledge of carburetor functions and willingness and ability to work with them is a skill I admire and would very much like to attain.
In what little time I have outside of running my one man small business and the endless "honey-do" list, I am reading all I can about 6 bbl carbs, single vs dual plane intake manifold designs and function, reading spark plugs, wideband O2 sensors/gauges/data loggers. I just invested $750 in Promax parts and I am sending them my carbs and the basics of the statistics on my 440 (not many mods, but I am going to convey them) so they can "pretune" them on their dyno mule that will hopefully get me close to where I need to be.
After I got my outboard carbs opening properly, I have addressed the idle mixture screws on all 3 carbs with some success, but I know that there is room for improvement, and when a 6 bbl is working right-man, what a rush!

 

[68 HEMI GTS]

Thanks, I’ve learned a lot from my dad over the years plus some from the dyno work I did a Livernois. Lately I’ve been doing a lot of reading and just studying the parts. Once I installed the 02 meter in the roadrunner and bought a numbered drill set it was on. I just started testing carbs and messing with about everything circuit and bleed I could just to see the effects were. Tuning for WOT is easy. Tuning for good drivability and clean plugs with big cams and low vacuum is a challenge. I’m still learning as, you always should.

Some of the set ups on just the roadrunner in the last 2 years

4412 center with vacuum outboards. Went 10.95 through the mufflers

How the proform started out. 850

Next reincarnation of the proform, 1.45 Venturi. Still seemed small.

Screw it, let’s make the proform a 1050An. 10.92 through the mufflers

Well if a 1050/4150 is good, let’s try a 1050/4500!! Best carb to date for all out.

And lastly my highly modified mechanical six pack. Time to play with a different car... except for making that clutch pedal work again !!

 

[biomedtechguy]

Nice setups.
Naturally I am a 6 bbl fan.
There are reasons other than the 6 bbl (like the purple stripe cam, less weight, SureGrip 3.54 and now 4.10, manual transmission) why my 70 V-code Roadrunner with a 71 440 is faster, a LOT faster than the stock 4bbl 71 Charger R/T I had in 78-79. The Charger had to weigh at least 400 pounds more, 727 Auto and an open 8 3/4 w/3.23 gears.
Having said that, when I bought my Roadrunner the outboard carbs weren't opening. When I resolved that, wow. Just WOW!

 

[69 GTX]

Great info! Thanks for sharing!