TUNING A SIX PACK

[biomedtechguy]

The guy who I stole the intake mods from had a 12:1 TF240 headed 512 in a full steel 70 bee running 10.40’s. That helped make up my mind to try it. He was kind enough to share some really good pics of the mods. His manifold was ported by MCH. Same car but slower dial as it had iron heads in the pic. Real V code as well!

Beautiful car, I am pretty sure I've read about that engine and those intake mods on "another" MOPAR forum.
The factory dual plane 6bbl intake and carbs, with a host of mods and options, or the mechanical 3x2 carb setup, have produced AMAZING power and torque, and the Hughes website is a source for some of those results.

 

[cj's mopar]

Just to let people know inset my 451 for initial start of fresh rebuild to the specs above with new carbs from summit out of the box and the end carbs were not even contributing fuel and had to figure out why my EGT temps were so high. I had to set idle mixture to 1 1/8 out on all the carbs to get the thing to run. With 350 deg temps on all cylinders. I am posting this because everyone including my self leans on this article and for break in on a new motor it could cause you some trouble if you did not watch everything very close.

 

[rumblefish360]

Good notation my man.



FWIW/FYI The carbs are sent directly from Holley to Summit Racing or your address from Holley.

 

[biomedtechguy]

I had to set idle mixture to 1 1/8 out on all the carbs to get the thing to run

I'll piggyback that with the "caution" that the outboard idle screws are MUCH more reactive to any adjustments vs the metering block on the center carb.
I can't offer a ratio for comparison, but when you adjust the outboard carbs idle screws, I suggest using small, incremental adjustments.
I knew I had a problem when my 440 6bbl smelled like a refinery. I turned the center carb metering block idle screws all the way in (no fuel) and it idled better. I knew my outboard carb(s) were dumping in too much fuel at idle.
THIS WAS MY EPIPHANY:

 

[66Satellite47]

In the mid '70's 6 Paks were readily available at very reasonable prices, they usually didn't work real well on the street and very few knew how to tune them. Bio points out a very important point, those end carb mixture screws need attention. On my '69 1/2 end carbs, richening the idle mixture by 1/4 to 1/2 turn out from stock made an amazing difference. The off the line performance was much smoother at the strip and around the pits. Later I learned about the end carb throttle position. There is a small adjustment screw under the base plate to adjust the blade position at idle. That was also very important on my '70 carbs, in addition to the mixture screws. The '70 carbs worked the best for me for some reason. I used the A12 EDE aluminum manifold untouched.

 

[69 GTX]

sounds like it works pretty good. I’d consider modifying the stock intake If you go back. I worked the dividers down a bit on mine. I picked this mod up from a guy with a really good running six pack stroker. It seemed to strigten up some of the low speed manors and it flat screams at WOT. Then I seen a very similar mod on a dyno test on YouTube the other day.
View attachment 1203392 View attachment 1203393

Could you share some close up pictures & approximate dimensions for the intake mod?
Thanks.

 

[BeeFast]

I'll piggyback that with the "caution" that the outboard idle screws are MUCH more reactive to any adjustments vs the metering block on the center carb.
I can't offer a ratio for comparison, but when you adjust the outboard carbs idle screws, I suggest using small, incremental adjustments.
I knew I had a problem when my 440 6bbl smelled like a refinery. I turned the center carb metering block idle screws all the way in (no fuel) and it idled better. I knew my outboard carb(s) were dumping in too much fuel at idle.
THIS WAS MY EPIPHANY:
View attachment 1300290

Where are the air idle bleed holes located?

 

[66Satellite47]

The air bleeds are on the top of the air horn below the air cleaner flange. Little brass plugs with small holes.

 

[bigpetesbee]

As far as I know, Indy Cylinder heads has the best deal on 3 carbs or try Summitt Racing. I would buy new carbs and try them but save your carbs esp. if they are the original ones. You would probably have to adjust rear mixture screws on the new ones to 1/4-1/2 out. Once you get them dialed in, they will throw you back in your seat. DON'T put a 4 barrel on it. Rebuilding your set is pretty easy. Soak them in carb cleaner and lightly blast them with your air compressor.
Holley 37-396 Renew Kit Carburetor Rebuild Kit
Holley 37-933 Trick Kit Carburetor Rebuild Kit
View attachment 981705

Rvert nice looking job, my only advise to rebuilding them yourself which I have done to mine many times is if all your doing is re gasketing them easy peasy. But if these were anything like mine that someone tried to set up as a race sixpack ie: they drilled out the air bleeds took off the outboard diaphragms put some cool looking mechanical linkage on it, it screamed after about 3000 rpm but drivability was an issue under that, with that being said I found a gentleman in Indiana Phil Fish rebuilt mine and it runs like never has since 1980 when I bought it. If you do rebuild your own check base plates for level Most people crank the snot out of them and the bend slightly