The Six-Pack Manifold Thread

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The Six-Pack Manifold Thread

Post by Aussie Chrysler »

Not being able to decide whether to go six-pack or EFI, I ended up with both for my 408 small-block Mopar.
DSC_8290.jpg
The six-pack manifold came extensively ported from F&B Throttle Bodies, who do the conversion.
DSC_8288.jpg
I've read all I can find on six-pack manifold flow numbers and porting, but info is limited, as it's not a common topic.

I've got the Six-Pack Engine Handbook by Larry Shepherd, but it's not much help as there is no info on equalising flow on stock manifolds. Jetting recommendations do not indicate which ports flow better than others.

From what I've read, #1 and #7 (right-hand port in above photo) are the hardest ports to flow - does anyone know if this is correct?

The manifold itself can be ported and made to flow good numbers, but apparently the port spread stays the same: http://www.hotrod.com/articles/mopar-sm ... flow-test/

Looking at the manifold, I can see why #1 and #7 would be handicapped - they both have 90-degree bends from the outer carb/TB openings to the port. While #4 and #6 are similar, they are both in the middle, meaning they get more help from the centre carb/TB opening.

So what can be done - if anything - to even up flow? The manifold is already ported, so I'm assuming options are now limited. On a stock manifold, I'm guessing you'd want to work #1 and #7 heavily to improve flow while keeping the other ports pretty mild.

On this one, I'm really not sure where to start. Also, would there be anything to be gained by notching the dividing walls between venturies to even up pressure? Again, I'm assuming this isn't necessary because the dual/single-plane design means all ports are connected to each other somewhere along the line.

If anyone has any tips or experience with six-pack manifold porting or equalising, I would love to hear them!

I'm also wondering if it's worth running O2 sensors on all 8 cylinders (exhaust) - instead of right/left bank - to compensate for uneven flow. If #1 and #7 are the problem, then a left-bank O2 sensor might be able to compensate. The ECU I'm planning on running will be able to compensate for individual cylinders on a sequential fire basis with up to 8x O2 inputs and 8x injector outputs.

Thanks.
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Re: The Six-Pack Manifold Thread

Post by MadBill »

Once you've done what you can re equalizing flow, if it's at all financially feasible, I'd run 8 sensors and trim the fueling as needed. You'll be able to make significantly more power more safely, not having to richen the whole engine to band aid a lean cylinder or two.

The main purpose of a plenum divider (for simplicity, considering a single carb V-8) is to provide a sharper velocity 'pulse' to the associated venturis, thus enhancing low speed fuel atomization and distribution. With EFI this is a non-issue and I'd say any dividers should be removed for better, possibly more equal, flow.
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Re: The Six-Pack Manifold Thread

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With the six-pack, it's a bit hard to know what will work and what won't. It's clearly a good design for what it is, and I was hoping to achieve the perennial "holy grail" of drivability, economy and performance.

I expect to be a little down on power from the current M1/4bbl combo, but I'm also hoping the six-pack will still work like it should with EFI: that is, offer the long-runner torque and isolated intake pulse of a 180-degree dual-plane on the street, but with open-runner performance up top.

I understand fuel atomisation at the intake level isn't an issue on an EFI engine like it is on a carbed engine, but runner length, turbulence and port velocity still play a part, yes? So while I guess I'm open to notching the dividers - like other dual-planes - to equalise pressure within the manifold, I would have thought completely removing them might defeat the purpose of running a six-pack in the first place?

Obviously, if I knew the answer to that myself, I wouldn't be asking! :D
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Re: The Six-Pack Manifold Thread

Post by ProPower engines »

I noticed that you have what appears to be a #6 cross over fuel line between the to fuel rails.Do you think there will be enough fuel volume for the other side of the engine??

the reason I ask is I just finished up a 383 using the holley system and it was lean on the other side.I used a #8 cross over line and the issue went away =D>

I should mention this was a single 4 barrel style base plate not a 6pak set up.
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Re: The Six-Pack Manifold Thread

Post by Caprimaniac »

Instead of fuel crossover, it’s better to let the fuel in at the front, via an y, to both banks. Tie together at rear to a regulator.

It looks like this is a progressive system, just like the carb setup?

As you have injector in each runner- even if you cannot get the flow 100% equal on all runners, ypu can use individual cylinder control to get the afr right.

But- I’m not convinced- is it better to have correct afr in all cyls, and thereby different hp- output in each- or un same fuel amount giving the cyls the opportunity to equal output.... even if some will run fat? Made my mind up- correct afr wins. Fat cyls will be even more down in power.

Good luck on your porting mission.

Im fortunate to have a more forgiving six- pack setup, IR 6- cyl- much easier to get the flow equal.
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Re: The Six-Pack Manifold Thread

Post by In-Tech »

Caprimaniac wrote: Wed Feb 21, 2018 3:24 am But- I’m not convinced- is it better to have correct afr in all cyls, and thereby different hp- output in each- or un same fuel amount giving the cyls the opportunity to equal output.... even if some will run fat? Made my mind up- correct afr wins. Fat cyls will be even more down in power.

Good luck on your porting mission.
You had me for a sec, lol.

The beauty of a carb/plenum setup is the carb doesn't care, it does its' job and as long as everything underneath it does its' job.

Having 3d tuning ability will always help EFI. The sadness is most aftermarket ECU's don't allow this kind of tuning and those that do forgot that air temp and valve temp matters along with transport delay.
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Re: The Six-Pack Manifold Thread

Post by Aussie Chrysler »

6AN should be OK, as it's similar to 3/8", which is the fuel line I'm currently running with the carb (800cfm BG). I haven't decided whether I'll run a return line or a bypass inside/outside the tank (it will be an in-tank pump set-up), but if I do it will likely be 3/8" in and 5/16" out. The car runs 11s and has been dynoed at 440rwhp, so I'm guessing it's around the 520fwhp mark. 1/2" or 8AN seems like it might be overkill.
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Re: The Six-Pack Manifold Thread

Post by Aussie Chrysler »

Caprimaniac wrote: Wed Feb 21, 2018 3:24 amIt looks like this is a progressive system, just like the carb setup?
Yes, adjustable progressive mechanical linkage. The throttle bodies are all 48mm. The TBs, injector rails, hoses and fittings were all matched for a 500-55hp engine.

Caprimaniac wrote: Wed Feb 21, 2018 3:24 amMade my mind up- correct afr wins. Fat cyls will be even more down in power.

Good luck on your porting mission.

Im fortunate to have a more forgiving six- pack setup, IR 6- cyl- much easier to get the flow equal.
Individual injector trimming would be best, but there's obviously a little more cost and complexity involved. Having sensors and wires poking out of my headers like a hedgehog would also detract from the "old-skool" look of the engine bay (fuel rails aside).

If I could confirm the lean ports are both on the same bank (left side), then I could feasibly run dual O2 sensors knowing each bank will be in the ballpark. But it would really help to know - roughly - which ports flow what before I start planning this.

I could try to get the manifold flow-tested at a local shop, but not sure if they could accommodate the six-pack intake. At the very least, they would need to flow the middle TB and one of the outers for each 4cyls front and back. For true flow figures, I guess you'd need to flow through all three TBs at the same time
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Re: The Six-Pack Manifold Thread

Post by Aussie Chrysler »

Here's a top shot to give you an idea.
DSC_8294.jpg
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Re: The Six-Pack Manifold Thread

Post by turbo2256b »

#S IN THAT article dont mean that much to me Unless its flowed bolted to a cylinder head. Also what the cylinder head flows can have an affect on the intakes flow when bolted to the head. I have flowed intakes bolted to a head. Also when porting an intake the right side in most cases needs to be done different than the left. single dual planes are the worst to port but dual quad and 3 2bbls offer better access most single planes also. intake on my 302 dual quad started out with the same flow as a performer RPM. after 2 weeks 6 to 8 hours a night after work it flowed 35 more CFM than a VrJr that had the draft removed. it also flowed the same on each port 215 cfm bolted to a head that flowed 235 cfm.
Bolting a rpm to the head flowed about 160 average, a performer about 145 average, torqer II about 180 about the same for a VrJr.
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Re: The Six-Pack Manifold Thread

Post by turbo2256b »

flow test
These are flow numbers for IK 180 Brodix cylinder heads stock and after port work
70cc combustion chambers
Valves 2.02/1.60
Intake 180cc after port work 190cc
Gasket match In FP- 1204..........Exh 1404



____Intake flow_______/_______ Exhaust flow
____As cast___Ported_/__As cast____Ported______W/pipe
-Lift
.100__ 68_______71_______------________59_________59
.200_143_______149______112________128________128
.300_195_______210______149________168________181
.400_227_______262______167________189________208
.500_242_______288______175________198________221
.600_250_______292______178________203________232
.700_251_______290______-----________204________237



While at it flow tested a Torker II as cast bolted to these heads before and after port work.

before porting heads--------- after porting heads
----- lift----CFM-------------------------CFM
----.100----- 68----------------------------68
----.200----142---------------------------143
----.300----192---------------------------195
----.400----221---------------------------227
----.500----229---------------------------242
----.600----229---------------------------250
----.700----229---------------------------251
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Re: The Six-Pack Manifold Thread

Post by F-BIRD'88 »

Very cool... Another way to fly that you might try is using a Small block Mopar tunnel ram and make a new custom fabricated plenum top for it to fit the 3 ( six pack ) throttle bodies on top instead of 2x4 carbs. Add on the EFI fuel injector bosses as on yours.

Then you can try both (dual plane) six pack and tunnel ram style "Six Pack" to see which one serves you best. If you want the big top end the SIX SHOOTER tunnel ram will have the advantage. Both will drive very well with either 3 carbs or 3x2 EFI.
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Re: The Six-Pack Manifold Thread

Post by turbo2256b »

would start by finding out what your heads flow then bolt on the intake and do a flow test. runners on the intake not being tested must be taped off
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Re: The Six-Pack Manifold Thread

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Aussie Chrysler wrote: Tue Feb 20, 2018 9:54 pm On this one, I'm really not sure where to start. Also, would there be anything to be gained by notching the dividing walls between venturies to even up pressure? Again, I'm assuming this isn't necessary because the dual/single-plane design means all ports are connected to each other somewhere along the line.
You're not kidding when you say info on 6-Pack manifolds is hard to find. Hughes Engines does a lot of 6-Pack porting, but I am sure they are not willing to share.

I while back there was an article in one of the rags about modifying a Big Block 6-Pack for performance, one of the things they tried was cutting down the dividers, it turned it into a turd on the dyno. I don't know if that would hold true for EFI. I can't for the life of me find that article on line.

I have a complete BB 6-Pack sitting on the shelf, one of my future projects will be full porting, carb mods, and then a direct comparison to a big single combo. I will NOT be cutting down the dividers. :lol:
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Re: The Six-Pack Manifold Thread

Post by Aussie Chrysler »

F-BIRD'88 wrote: Wed Feb 21, 2018 2:23 pm Very cool... Another way to fly that you might try is using a Small block Mopar tunnel ram and make a new custom fabricated plenum top for it to fit the 3 ( six pack ) throttle bodies on top instead of 2x4 carbs. Add on the EFI fuel injector bosses as on yours.

Then you can try both (dual plane) six pack and tunnel ram style "Six Pack" to see which one serves you best. If you want the big top end the SIX SHOOTER tunnel ram will have the advantage. Both will drive very well with either 3 carbs or 3x2 EFI.
Weiand has already thought of that.
Image

Only problem is there is no SB version - only BB. However, there is a ton of information on this manifold both in The Six-Pack Engine Handbook, as well as Victory Library, here: http://victorylibrary.com/mopar/weiand-c.htm

The interesting thing about The Six-Pack Engine Handbook is that it gives jetting recommendations for the Weiand and Edelbrock STR-14-6 - another 6-pack common plenum design below:

Image

Jetting recommendations for both manifolds favour either the left or right corners of the end carbs to equalise fuel distribution. However, for a stock Mopar 6-pack manifold - both SB and BB - the book does not recommend unequal jetting (the end carbs actually have metering plates).

This suggests to me that unequal fuel distribution isn't a serious issue for the six-pack manifold. This information appears to be backed up in other Mopar books I have read.

In any case, the above manifolds are both single plane (cross ram) designs that are built for top-end racing without the benefits of dual-plane runners for the street - which was obviously the idea behind the original six-pack design.
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