Rebuilding the 6-Pack this Winter

Chargered · Oct 27, 2020

My winter project this year will be rebuilding the 6 pack carbs. I've been running this set up for about 10 years now and the guy who owned the car before me had been running it for many years prior to that. So my guess is these carbs haven't been touched for 20-30 years. Its done okay for me for the past 10 years, but in the past 1-2 years it has started to run very rough on the idle circuit.

As you can see in the pics, this is the old Direct Connection Hustle Stuff 6-pack set up. The outer carbs have the accelerator pumps and no idle adjustments. I'm considering switching this over to the factory vacuum operated secondary set up. For you guys who have experience with 6-packs, any recommendations on whether I should stick with this or convert over to the factory set-up. I think I would have better adjustability/tuning with the factory set-up. This is mostly just a street driven car. Your thoughts?

biomedtechguy · Oct 27, 2020

Let me know if you want to sell the old parts.
I had all 3 of my Holley 2bbl carbs that were running pretty good modded and rebuilt/gone through by Promax. I have their center carb metering block, which works well and is much more flexible for hotter than stock cams. Also if you switch over to the vacuum actuated outboard carbs (they work great when you have the right springs in the pods) you will want to have the angled idle mixture screws on the rear carb throttle blade plate that Promax makes, and if the front screws have lead plugs remove the lead so they can be tuned.
THIS information changed what having a factory 6bbl means from a tuning hassle to an epiphany:

Zoomed in on the critical data:

This is the rear plate w/angled idle mixture screws:

Chargered · Oct 27, 2020

biomedtechguy said:
Let me know if you want to sell the old parts.
I had all 3 of my Holley 2bbl carbs that were running pretty good modded and rebuilt/gone through by Promax. I have their center carb metering block, which works well and is much more flexible for hotter than stock cams. Also if you switch over to the vacuum actuated outboard carbs (they work great when you have the right springs in the pods) you will want to have the angled idle mixture screws on the rear carb throttle blade plate that Promax makes, and if the front screws have lead plugs remove the lead so they can be tuned.
THIS information changed what having a factory 6bbl means from a tuning hassle to an epiphany:
View attachment 1019607
Zoomed in on the critical data:
View attachment 1019608
This is the rear plate w/angled idle mixture screws:
View attachment 1019609

Good advice. If I go the factory vacuum route, I'll definitely get that Promax base plate for the rear carb. I think I might have better luck on the street tuning the factory set up. I just need to decide if I want to keep my current set up or change it over to factory vacuum actuated (I think buying all the parts will be a bit expensive).

biomedtechguy · Oct 27, 2020

Chargered said:
(I think buying all the parts will be a bit expensive).

But that cost can be offset by a guy who is interested in your old parts since he has a Weiand P3690982 6bbl Super Stock intake and is building a 541 stroker...
:thumbsup:

Chargered · Oct 27, 2020

biomedtechguy said:
But that cost can be offset by a guy who is interested in your old parts since he has a Weiand P3690982 6bbl Super Stock intake and is building a 541 stroker...

Just curious, you can't use the factory set up with that Weiand super stock? What would be the driving reason to use a mechanical set up on that? ……….. (trying to learn the good and bad of both options)

biomedtechguy · Oct 27, 2020

Chargered said:
Just curious, you can't use the factory set up with that Weiand super stock? What would be the driving reason to use a mechanical set up on that? ……….. (trying to learn the good and bad of both options)

I plan on using my 6bbl w/the Promax mods to lend toward flexibility in tuning, and my dual wideband O2 sensor system to be a tool to judge the results.
From the insane amount of research I've done on 6bbl and performance modifications, I am interested in having the type of setup you have as an option, but I do plan on making the most of what I have already heavily invested in and familiarized myself with.
It would be difficult for me to spend much on parts to convert to the setup you have when this is the "other option" that I am most inclined to pursue should I feel like my current setup, modded to its greatest capabilities, should leave me wanting for more. This setup takes away the biggest negative inherent in the Weiand intake, fuel atomization and distribution and fuel pudding, right OUT of the equation by making it a dry system due to direct port injection:

Picture that on the polished finish of that intake, that looks like this:

and I can get ALL of that done by F&B...
There are a couple of Mopar guys who have done this exact setup, but I don't know of any that have their projects running yet.

BSB67 · Oct 27, 2020

There is no reason you cannot get the mechanical carbs to run well. Generally, they will perform better than the factory vacuum. And, I would never sell those carbs. My 2 cents.

Chargered · Oct 28, 2020

BSB67 said:
There is no reason you cannot get the mechanical carbs to run well. Generally, they will perform better than the factory vacuum. And, I would never sell those carbs. My 2 cents.

Thanks. That is the kind of feedback I was looking for. I'm leaning towards just sticking with my current set-up.

RJRENTON · Oct 28, 2020

BSB67 said:
There is no reason you cannot get the mechanical carbs to run well. Generally, they will perform better than the factory vacuum. And, I would never sell those carbs. My 2 cents.

Out of curiosity, your quote: "they will perform better than the factory vacuum", relating to the mechanical carb configuration, how was this determination arrived at....dyno runs or ET slips or "seat of the pants" feel? Since I'm a proponent of origionality, my choice is the vacuum actuated set up, especially for a mostly street driven vehicle, with subtle modifications that, to the average person, would be undetectable. These modifications would be the Promax throttle body for the rear carb and the screw in metering jet plates for the front and rear carbs, to allow for stagger jetting of these carbs, which in my opinion, significantly improves fuel mixture distribution issues and subsequently "fixes" any WOT fuel distribution problems, which is difficult to achieve with the factory metering plates. Just my opinion of course.
BOB RENTON

BSB67 · Oct 28, 2020

Track results

biomedtechguy · Oct 28, 2020

RJRENTON said:
Out of curiosity, your quote: "they will perform better than the factory vacuum", relating to the mechanical carb configuration, how was this determination arrived at....dyno runs or ET slips or "seat of the pants" feel? Since I'm a proponent of origionality, my choice is the vacuum actuated set up, especially for a mostly street driven vehicle, with subtle modifications that, to the average person, would be undetectable. These modifications would be the Promax throttle body for the rear carb and the screw in metering jet plates for the front and rear carbs, to allow for stagger jetting of these carbs, which in my opinion, significantly improves fuel mixture distribution issues and subsequently "fixes" any WOT fuel distribution problems, which is difficult to achieve with the factory metering plates. Just my opinion of course.
BOB RENTON

@RJRENTON ,
I have the jetable metering plates, and for now, the factory dual plane 6bbl intake. I also have a Chrysler Performance book that deals with the Weiand P3690982 6bbl CrossFlow Super Stock intake, and jetting for the stock intake.
What kind of staggered jets are you using and what mods are in the engine?

biomedtechguy · Oct 28, 2020

Chargered said:
I'm leaning towards just sticking with my current set-up.

BSB67 said:
I would never sell those carbs.

Hey man! I'm trying to get a deal!

I actually have a source for allegedly "NOS" carbs like the OP has from the guy I bought my Weiand intake from, BUT after the first intake he sent me not being the one in the pictures he posted, and it was such a mangled intake I immediately sent it back, but fortunately he had a 2nd unmodified one that's very nice that I wound up with, I would proceed very carefully if I move on a deal with him, like lots of pictures of the actual carbs he intends on selling.
Then again, that F&B EFI/DPI setup sure is sweet!

RJRENTON · Oct 28, 2020

biomedtechguy said:
@RJRENTON ,
I have the jetable metering plates, and for now, the factory dual plane 6bbl intake. I also have a Chrysler Performance book that deals with the Weiand P3690982 6bbl CrossFlow Super Stock intake, and jetting for the stock intake.
What kind of staggered jets are you using and what mods are in the engine?

The RS23V0A****** GTX is fairly origional, with these simple changes:
1. 0.030 over with 906 heads bronze guides std size valves
2. Crane equilivant to the Mopar 292° 0.509" with 1.6 ratio roller rockers @ 4° Retarded
3. TRW forged pistons w/ advertised ratio of 11.1 with valve reliefs with 0.004" clearance and moly filled rings, full floating pins and Waldes Tru-Arc retainers.
4. Clevite 77 tri metal bearings (full groove mains) @ ~ 0.0025" clearance and 0.002"-0.0025" rod bearings.
5. ARP HARDWARE holding it together.
6. High VOLUME oil pump running 10W-30 Mobil1 with ZDDP. Yielding ~ 75 psi hot at 3000 RPM and 60 psi hot at ~ 1100 RPM.
7. ORIGINAL Prestolite dual point distributor (recurved) with ~ 36° total advance all in by 2400 RPM no vacuum advance, Champion UJ-11G or HO-8A non projected nose plugs @ 0.035".
8. 180°F t-stat with Flowkooler pump, 2806070 fan clutch 7 blade fan with shroud 2998956 rad running 60% Dexcool/Water.
9. Holley vacuum actuated carbs...center carb w/ #66 main jet, std PVCR, 6.0" PV, End carbs... I'll have to review my notes as they were rejetted front to back, side to side (slightly richer) due to increased Ethanol content in the fuel
10. 4.10:1 Dana 60 rear A833 18 spline transmission. 275 x 60 x 15" tires.
The car has been in storage this year due to the Covid problem....just nowhere to go.
Anything more specific and I'll have to dig out the notes....
BOB RENTON

Chargered · Oct 28, 2020

RJRENTON said:
Out of curiosity, your quote: "they will perform better than the factory vacuum", relating to the mechanical carb configuration, how was this determination arrived at....dyno runs or ET slips or "seat of the pants" feel? Since I'm a proponent of origionality, my choice is the vacuum actuated set up, especially for a mostly street driven vehicle, with subtle modifications that, to the average person, would be undetectable. These modifications would be the Promax throttle body for the rear carb and the screw in metering jet plates for the front and rear carbs, to allow for stagger jetting of these carbs, which in my opinion, significantly improves fuel mixture distribution issues and subsequently "fixes" any WOT fuel distribution problems, which is difficult to achieve with the factory metering plates. Just my opinion of course.
BOB RENTON

You mentioned you prefer the factory set up "especially for a mostly street driven vehicle", which mine is mostly 98% street driven. What makes the factory vacuum operated system better for the street over the mechanical? Just trying to learn the pros and cons. By the way, mine is a 4 speed with 3.23 gears.

RJRENTON · Oct 28, 2020

Chargered said:
You mentioned you prefer the factory set up "especially for a mostly street driven vehicle", which mine is mostly 98% street driven. What makes the factory vacuum operated system better for the street over the mechanical? Just trying to learn the pros and cons. By the way, mine is a 4 speed with 3.23 gears.

Personally, with the vacuum operated carb set up, the engine will determine the opening point of the end carbs based on air flow. Unless you have deep gearing that allows the engine to build RPM faster, IMO, it's too easy to over carb the engine and create a "bog" or flat spot in the acceleration curve, until the RPMs build. Too much air flow results in lower intake mixture velocity....possibly determined by the rear end ratio and the cam's profile and rate of change the distributor's advance curve. I think that mechanical opening carbs are best suited for the strip in a light weight car or if automatic transmission equipped with a higher stall speed torque converter, and rear gear....but....its up to the individual's preferences. I guess that the origional application was invented for the street...was the reason Mopar selected vacuum operated carbs. Even the Hemi used on demand AFB carbs, using velocity operated secondary butterfly valves.....so, do what ever suits you....
BOB RENTON

4406bbl · Oct 28, 2020

There is nothing wrong with those carbs since they have outer pumps, only reason to switch them would be to get the original look. I will only add this, when you rebuilt them the style of needle and seat you have are notorious for cleaning the threads out of the bowl when you remove them. Hold the needle with a screwdriver, remove the adjusting nut, squirt a little penetrating oil on the bowl and seat threads, let it sit a while to get oil down to the o-ring, work back and forth slowly. You will need 3 new adjusting screws and nuts, as the late style is different.

biomedtechguy · Oct 28, 2020

RJRENTON said:
Anything more specific and I'll have to dig out the notes.

Lol...
I appreciate the reply.
I am most interested now that I know what mods the engine has as to what jets you're using in the front and rear outboard carbs. We have the same basic cam.
When you get a chance. Thanks.

Chargered · Oct 29, 2020

RJRENTON said:
Personally, with the vacuum operated carb set up, the engine will determine the opening point of the end carbs based on air flow. Unless you have deep gearing that allows the engine to build RPM faster, IMO, it's too easy to over carb the engine and create a "bog" or flat spot in the acceleration curve, until the RPMs build. Too much air flow results in lower intake mixture velocity....possibly determined by the rear end ratio and the cam's profile and rate of change the distributor's advance curve. I think that mechanical opening carbs are best suited for the strip in a light weight car or if automatic transmission equipped with a higher stall speed torque converter, and rear gear....but....its up to the individual's preferences. I guess that the origional application was invented for the street...was the reason Mopar selected vacuum operated carbs. Even the Hemi used on demand AFB carbs, using velocity operated secondary butterfly valves.....so, do what ever suits you....
BOB RENTON

Thanks Bob, that explanation really helps me understand it better now.

62MAX · Oct 29, 2020

4406bbl said:
There is nothing wrong with those carbs since they have outer pumps, only reason to switch them would be to get the original look. I will only add this, when you rebuilt them the style of needle and seat you have are notorious for cleaning the threads out of the bowl when you remove them. Hold the needle with a screwdriver, remove the adjusting nut, squirt a little penetrating oil on the bowl and seat threads, let it sit a while to get oil down to the o-ring, work back and forth slowly. You will need 3 new adjusting screws and nuts, as the late style is different.

As your comment on needle/seat threads,you would be amazed how many I get with stripped threads.If I get six sets,I guarantee you that at least two bowls will need inserts,same with end base mixture screws with half the head broken off,then they try and drill,end result,also needs an insert. With the cost of these parts if you can even get them,about all you can do is fix what you can.

Chargered · Oct 29, 2020

Lots of good feedback here.
Okay so if I do go to the factory vacuum set-up, would you guys recommend I just buy a new set of carbs, or take my Direct Connection carbs and rework them with new bowls to get the fuel inlet on the other side and new base plates with the idle adjustments? I would also need to buy the vacuum pods and all the linkage, brackets, springs, choke mechanism and idle solenoid. Anything else I'm missing?

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