Stroker BB 6 pack jetting

Hi Guys,

I have a 512 stroker and was wondering what people were running for jet sizes in their 6 packs? Motor was dynoed but we were still a little lean at 55 to 6 grand. My builder wanted to leave things alone while the dyno guy was insisting to do more pulls but we were on the dyno for a while and fought a phasing issue and I was pretty happy with the power 610 hp - 649 torque however the builder was shooting for 650 hp. Maybe left something on the table using this intake?

Motor is 11.2-1 compression, Promax cnc'd heads 330 flow on the intake side at 600 lift, Eagle 4.25 crank, Eagle rods 7.1, 260@ .50 solid flat tappet cam-crane-.600 lift, 1.5-1 roller tip ss rockers-crane,CP flat top pistons, 1969 aluminum 6 pack with vacuum secondaries-66 jet on the main and 81 on the end carbs all corners with promax metering plates. I am at 3500 feet above sea level.

Thanks for your input.

jet up on the center

My low deck Eddy dual plane six pak intake 400 block 512 C.I. 9.25 to 1 compression liked .092 on the drivers side and .096 hole size on the passenger side on both outboard carbs running and testing on 91 octane CA pump swill years ago I did run a set of 1970 440 carbs modified with the stock outboard metering blocks modded so I could change the set screws in the bottoms to bigger or smaller I.D., I used Holley #63,64 and finally 65 jets in the center carb. That motor had a custom ground solid roller cam with 260 @.050 intake side and 266 @ .050 on the exhaust ground on 108 LSA installed at 107 ILC with a set of Harland Sharp 1.6 ratio roller rockers. It made 612 HP and 644 Ft lbs with a set of large valve ported iron 906 heads back then, it ended up making 727 HP with similar torque after changing the heads to a set of Indy SR M.W. heads and single Indy 400-3 inatke with a 1050 Holley dominator carb, this was with 518 C.I.(4.300 stroke to raised the pistons up to zero deck height to increase the compression ratio) and 10.78 to 1 compression I love Mopar Wedge strokers, not so much with Hemiroid motors

mopars bulletin#2 june 1971 440 6bbl race setup: throttle side dia. side

front- .093" .089"

center- #65 #65
pvcr- .052" .052"

rear- .093" .099"

Cab - what elevation were you at with that motor? I'm at 3500 feet. I have plans to chassis dyno tune the car when I find some time this summer. I welded bungs in when I installed the exhaust. Thanks for the feedback.

Was any work done on the intake to improve the flow? Those old 2-plane Edelbrock intakes are capable of making some prodigious amounts of power, especially if you do some deep porting on them.

I have one on my 493" wedge with the mechanical secondary carbs making 715 hp at 5500 rpm. It was deep ported by Hughes Engines, and is bolted to a set of Hughes Stage 2 ported small port Indy EZ's. I'm running a smallish hydraulic roller.

The wide band was indispensible as far as dialing in the jetting and squirters. I found no need for a chassis dyno and dialed it in on the street using the data logging feature. It makes it pretty easy to do. My hat is off to the guys who dialed them in by the seat of their pants and reading the plugs. Now, that takes some skill!

Intake was port matched and also some extensive porting as well. Whether the builder did a good job - who knows? I never thought about installing a wide band gauge. Dialing it in on the street would be a lot more fun!! We thought with this cam and heads the motor would put out a little more hp...however it is just a street car that will never see the track but even so, making this thing run correct is important.

When I built and dynoed it the first time it was in Ontario, CA which is right at 800 Ft. I lived up in Hesperia,CA which is around 3500 Ft. I moved to Bend before the car was driveable and did most of the final tuning up here in Bend,OR between 4300 ft and 180 ft at Woodburn drag strip. I did put a wideban on the car and used it for testing the timing, spark plug heat range and the outboard jetting I never had to change the jetting for different elevation, I should have, but it ran fine so I didn't

Like Cab said 65 or 66 jets in center carb and this big engine likes fuel and respond to it so go up 2 to 4 steps on the sqirter on center carb ! You will feel the differens. On the outer carbs i ended up with 82-84 jets so i gues Cab reved his engine more than i did. If you realy whant to have fun with the six pack set up look for the mecanikal carbs that whas sold thru Direct Connetion whit list number 82&83 or if you can find the BG carbs that i run now that respond way better !

here is my 2 cents.....(take it for what its worth)
440 stroker 500ci 11.2. comp ported eddys hughes custom 650 lift ported six pack 70 center front 84 choke 88 throttle
rear 88 choke 90 throttle...when the six pack opens it pulls like a freight train

I read the BG carbs are significantly smaller than the Mopar Holleys. I love the DC mechanical carbs, but you have to know how they like to be driven. Nothing mysterious, but you can't mash them open at 2000 rpm and expect the port velocity to be high.

Thirsty beast! How did you tune yours if you don't mind me asking? Pulls like a freight train sounds good to me...I haven't had a chance to drive mine yet - I have been out of the country for the last 6 weeks and will be here another month or so. I think I will throw 84s up front and 88s in the back and hook up an AF gauge and go from there judging by what everyone else seems to be running. I was just checking on line and I see there is a remote one available usable through your smart phone if you don't want a gauge in the car - sounds kinda cool. Appreciate the input from everyone!

Stagger the jetting for the manifold, don't use the same size jets in the outboard carbs My carbs had the stock metering plates modded to accept # 6 brass set screws drilled to those numbers, which I opened up .004 on both sides to make it richer. If your using Holley jets or Holley air bleeds as your jets look at the hole size and go from there Remerber though it is way safer to start off richer than needed instead of to lean

You have been missinformed ! The flow are rated dry on some and wet on some so thats why the numbers vary but i have flow tested the outer stock Holley carbs that is rated to 500cfm and the BG carbs are only about 4 cfm under those BUT the center BG carb flow the same amount so al 3 carbs together in flow numbers the BG would be bigger and i can open mine from 1500 rpm to full in a 4 speed Challenger without any hesitation what so ever on a RB stroker of 505 cubes whit same cam as you use from Hughes so i gues you need to tune more then !?

First thing holley jets out of the box are no where what the number says.. Try to get a set of pins and gauge the jets.. I run 84/86 on a stock stroke 440 with 906 heads that are cleaned up with a good valve job.. 11.97 comp. with a hyd flat tappet cam..
For instants the 86 jet is my 84.. Sounds like you are very lean.. Good luck..

I think he is referring to the old DC mechanical carbs, those end carbs flow more than the stock vacuum 6 pack end carbs. They are basically a 850cfm DP cut in half, they have the slabbed throttle shafts. Flow is around 1050 to 1,100 true CFM.

I can floor my DC mechanical 6bbl off idle and no bog, cough, backfire.. Just acceleration!!! I do have it on a tiny 365ci maybe 400hp demon with a 4,400rpm stall and drag radials! My A/F meter still showes it lean at WOT 13.5 with 77/78's on the end carbs, 64 center.

Not how Holley`s work unlike BLP or maxi-jets where the number is the actual size.........two different animals..........

forgot to add I purchaced quick fuel metering blocks they make a kit for the six pack. Also didnt want to drill anything out and make a mistake ,and everbody I know that purchased the (other guys plates) had major issues. Im not saying my seup is perfect its working... ps cabis correct when mopar dynoed the six packs in the 69-70's they found staggering worked better.
thanks

Are you shore that the DC mecanical carbs list number 82 and 83 outer carbs have bigger venturi than the stock vacume !? i own two NOS sets of those and the throttel blades shore looks smaler on al 3 DC carbs ! Any way my BG six pack carbs as i stated before flow the same becaus they are same body and just about 4 cfm under the stock outer vacume carbs so they would have bigger flow numbers than the stock al 3 together as the stock center carb is way smaler than the outer carbs and they just work fantasic.

Perhaps there's a bit of a communication barrier between our posts regarding my statement. Opening all six barrels without a bog, hesitation or mis-fire at low rpm is not the issue. With the help of a wideband, I'm pretty confident my tune is pretty sharp at this point with the motor cranking out a respectable power curve beginning with over 500ft lbs of torque at 2000 rpm and culminating in 715 hp at 5500rpm. The drivability is excellent as well, especially with a Passon 5 speed and 3.73's.

In my comment about knowing how to drive them, I was referring to the concept of a driver keeping the velocity through the venturies at the maximum rate. Obviously, it varies depending on engine rpm and throttle blade positioning. You must be aware of this, and it's affect on power output during an rpm increasing throttle event. If the driver's ability to vary air velocity through the carbs isn't an issue, especially at low rpm, then why not adjust the progressive linkage to have all 3 carbs open at once?

John one of the resone you dont open al 3 carbs in a lockt linkage is fuel consumtion but if you recurved the carb i gues you could but thats the resone there is a progresive linkage in a normal multipel carb system regarding your statement on that the BG six pack set flowing less than the original or 82-83 carbs you are wrong if you put al 3 carbs together and compare becas the BG will out flow both sets but for some resone BG state there flow rate wet and Holley dry mabee you have a to lean fuel curve on fast throttel opening or your retracted electrode on your sparkplugs dont like the low rpm or maybe you runners in the intake are to big for low rpm flow !? a stroket b&rb block almost always responds positive to more fuel and i stay away from rectrakted plugs on street and strip engine becas they only work great on hi reving engines if you realy whant max power out of the engine you need to race against the clock on the strip and try to jet up or down on the strip regardles of what the wideband say !

You are still missing my point. You are obviously well-informed. It's all good. My tune is fine.

If you say 3 - 250cfm rated BG carbs flow more at 3" of vacuum than the three Holley's 960 cfm rated do at the 4-barrel rated measurement of 3" of vacuum; I'm not going to argue with you about that. You might have better measuring equipment than BG or Holley.

However you came up with your flow ratings, the physical size of the throttle openings are in the BG's, are physically smaller, which is what I originally said. I understand that you believe they flow more, and you could very well be right. But, we are continuing to have some sort of communication issue, which is ok. It sounds like you are having great success with whatever it is you are doing, and I always enjoy hearing about Mopars being hot rodded in other countries.

You sure you have the right outer carbs mine are exactly like a 850dp, and the throttle blades are the thin type with slabbed shafts, stock 6 pack carbs have thicker throttle plates with full round shafts.

John im gona try to explain this one last time then i give up !

Barry Grant mesiure and rate there wet flow and Holley mesiure there rate dry flow ! There is a hughe differens in numbers as if you rate the flow wet the numbers falls down compared to dry flow as Holley do so the numbers you are refering to if they are corekt (250cfm) is a wet flow !

I can reashore you that i do know what im doing and have been doing for the past 15 years on race car engines in development and inproving them.

Reply to ademon !

Im pretty sure but im not home ! Im dead shore they are the DC sold list number 82-83 carbs and i do have two NOS sets that never had fuel in them and one NOS throttel linkage that are realy rare to find ! I will look close at them when i get back home again. Do you know the size of your throttel blades ?

Ok, Ok, since you keep wanting to focus on every issue but what I am talking about, I did some quick research on the flow ratings of both carbs.

There is at least a 210 cfm difference between the stock Holley carbs compared to the BG's, and possibly even more of a difference between the mechanical secondary DC carbs, especially with a milled choke horn. So, its also a commonly accepted fact in all the information I found that a wet flowed BG 750 4-barrel is the equivalent of a dry flowed 850 Holley 4-barrel. If this holds true, your still only talking about 100 cfm more.

If that is in fact the case, then there is no way the BG's flow more. There is a 210 cfm difference between the 960 cfm dry flowed Holleys and the 750 cfm wet flowed BG's. Maybe you've out research both Holley and BG in your 15 years of experience, but you haven't convinced me at this point, but then again you already gave your last gasp attempt at educating me. I do appreciate your efforts, and assure you I mean no disrespect.

John im just trying to tell you the facts ! I dont know were you find your numbers to compare and witch carbs of BG six shooter you find numbers on becas he made some for Chevy sb that maybe is smaler i dont know but i flow tested the so caled 500cfm Holley stock outboard carb and compared that to the flow test i made on the outer BG carb and the BG carb flowed about 4cfm less than the Holley did al in a flow bentch but the center BG carb is as big in the venturi as the outboard BG´s so what im still trying to tell you is that if you put al 3 carb together the BG carbs must flow more on full throttel than the Holley stock set as the center Holley stock carb is smaler than the outer as it is rated at 350cfm. The ones i use were sold only for Mopar engines and sold thru INDY and some other vedors like Jegs i gues.

I have not flow tested the DC carbs so i have no cold hard facts on those but i will some day !

I mean now dissrepect of any kind to you or anybody else im just trying to present the facts i found out in a flow test but you still say that it isent so ! If you still dont beleve me flow test your self !?

This is starting to get realy rediculess so i rest my case here and now.

Good enough. Thanks for posting.

Ok John here it goes,

I have now flow tested the NOS over the counter DC sold 82&83 carb for you and spent some money doing it but i can live whit that !

Al numbers are cold facts and you are welcome to do the test your self. Al dry flow test have been done at 28" and in same place on same fixture.

The DC center carb flow 326,4 cfm and the outboard flow 553,6 cfm so that set of al 3 carbs will flow 1433,6 cfm.


The out of the box BG six Shooter carbs for Mopar flow 510,5 cfm on center carbs and outboard carb flow the same so al 3 carbs together will flow 1531,5 so yes i whas right al along the BG flow more.

I also flow tested the stock replacement outboard carb for 440 and it whas 532,6 cfm but i dont have any spare stock center carb that i can test at this moment.

Hope this whas educating and thanks for posting.

That thinking doesn't matter.........OF COURSE the Holley jets aren't sized as the #`s say because they use the LENGTH and TAPER on the inlet/outlets of the jets for flow. Kinda like vacuum at idle and pv`s...........

How come stroker 6-pack guys don't look at the Holley 4412's for the center carb? They flow 500cfm out of the box.... And them roundy, roundy, guys have a few outlaw carbs that flow well over there 500cfm rating cfm. Just mill off the round back section so that the six pack base can sit on top call it done and few look twice?

Just wondering.....

There are more than one street sixpak set up running like that In fact Holley use to make a 600 CFM two barrel for roundy round racing that had no venturi boosters in them at all, the fuel was fed through the sides of the main body
The Carb Shop in Ontario,CA was buying those 500 CFM carbs. new and converting them for six paks many years ago back in the early 2000s

Thanks, if I were doing any 6 pack, big or normal that's the direction I would go in (4412) and no one would be any the wiser. I see 4412's going for dirt cheap on flea bay. You could even send it out for a tweek or two and still be into it cheaper than a new 2300 center pot.

Even the hard core six-pack guy's don't catch them, even when there starring directly right at them 2ft away.

That's my .02 worth.

Them 500 cfm 2 barrels don't work on strokers ... my new 511 I just built

SHHhhhhh, I wasn't going too tell anyone.. Back too your hole!

Cab i whas considering the roundy carbs when i whas looking for carbs that could breath better and mostly the center carb that realy made my stroker more alert up to 3200rpm so the throttel response inproved alot ! I just found these BG on Fle Bag first and became intrested as they are more uncommon i gues !

I even tryed to find some more cfm on the outer carbs by stratening out the venturi on those in a spark machine but i only made about 17 cfm doing that stunt

I was under the impression that the BG six pak carbs flowed less than the stock Hollet six pak carbs did I'm glad you helped straighten that myth out Thanks a LOT

My six pack had a 4412 center carb.

And Barry Grant is a hack

I don't think the 4412 has the vacuum hose provisions for diaphragms on secondary end carbs; now mechanical sec. end carbs yea they may be a good choice.

This is going back sometime, but Dunnuck was looking into doing some deep porting Six Pack testing. I think he fell of the face earth as I haven't seen him post in a long time?

Correct, however the boss is there in the main body and would require drilling. Take a second look at 68 Hemi GTS picture, its right there....

Well, this thread certainly has a variety of theories in it.

The easiest way to (roughly)compare two barrel and four barrel holley style carbs for flow capacity, since they are tested and rated at different pressures, is to compare the Venturi and throttle bore diameters.
For example, a secondary OE 6bbl carb has the same size venturi and throttle bore of an 850dp Holley # 4781. A 4412 is the same as a 750dp Holley # 4779.
In other words, when tested under the same parameters, 2 4412 Holley carbs don't flow 250cfm more than one 4779. The 2 4412's basically flow the same as a 4779....... Or roughly 375cfm when tested at the 4bbl pressure.

To the OP........ Compared to the stroker 6bbl motors I've tested, that jetting would be pretty lean. For the power levels you're at, we usually end up with secondary jets in the mid-80's.
I also agree that with 330cfm heads on a 11:1 shortblock and a 260 @ .050 cam you should have seen a bit more power. 650?? Who knows...... Dynos can vary a lot, but 610 seems like there might be some left on the table.

Just wondering where did you get two 4412's? The 4412 has a factory rating of 500cfm however they rated at, and it replaces the center carb.

Let me rephrase, do you think that a 4412 in the center would move more air than the stock six-pack center?

I was using the two 4412's as an example to compare to one 750 4 bbl.
The two 4412's equal the one 750 in terms of Venturi area and throttle bore area.
Does it seem logical that the two 4412's would flow 250cfm more than the 750?

Does a stock 6 pak center carb flow more or less than a 4412?
Look up the Venturi diameter and throttle bore diameter for both, then you tell me.

The stock center for a 440 is a 4144 carb, it has a 1.187 venturii and a 1.5 throttle bore for 350cfm. The 4412 has a 1.376 venturii with a 1.688 throttle bore for 500cfm. So I say that the 4412 moves more air. This was from Holley's web sight.

ayye aye cap .. love my Lm1 and 2 great to have these tools today .

Yep, my junk was runnin low 10`s till I chassis dynoed it w/air fuel capabilities then right into the 9`s............invaluable tuning AID not end all but a directional tool......

the "real" 6bbl flow numbers were 250cfm center and 390cfm for each end carb. venturi area is a little over 9.8sqin's. i don't get overly lost in cfm numbers because they're manipulated, but you can't lie about venturi area.