The Dodge Challenger Message Board

I promist Ade i would post what i discover on the BG carbs and what i do to them so here is the start of that topic and feel free to jump in if you guy´s think im wrong !

I tock the outer carbs apart as i have to make them bigger in there venturis becas they are rated to 355 cfm so what i will try is to copy the opening area from the Holley´s 500 cfm carbs into the BG´s and i mesiured the openings on the BG to 35,2 mm and the Holley whas 40,3 so i will try to make a electrode at work and do this in a spark machine as i do not whant to drill out and take of the anual booster´s in the BG carbs or i could mill up the venturis ! The pic show the carb body from the BG close to a Holley outer carb and as you can see the anual booster in the BG is bigger and it has 8 feeding holes under it !

One other thing i havent seen before that stumbels me a bit is the center Holley carb has an venturi opening area (Diameter) of 30,7 mm so how can that carb flow 355 cfm !? That can not even be close but mabee 290 cfm !?

I will try to post more later when i have made more on them and i also plan to cut of the choke tower on al carbs to inprove the flow !

Good topic Pat thanks for takin the time to post it up
My first question is why are the BG carbs that much smaller than the Holleys? Is it for signal strength?
Secondly, exactly what was the true flow rating of the factory setup?

Holley rates their 2bbl carbs differently to their 4bbl carbs. They use a different pressure difference.

100 cfm on a 2bbl is only 71.4 cfm on a 4bbl.

So a six pack outer carb rated at 500 cfm is only really equivalent to a 375 cfm 4bbl

The middle 350cfm Holley is only really 250 cfm in 4bbl terms.

So the 1350cfm six pack is the same as a 964cfm 4bbl. Just as well really because otherwise it would be too big for a stock 440 and WAY too big for a 340.

Now, I can't remember exactly but I have a feeling BG rate there carbs in a slightly different way to either Holley type.

You can't go just by size. A smaller opening can flow just as well as a larger one. The air can just flow faster in the restriction which improves signal strength and mixture quality.

The ONLY way to know for sure is to use a flow bench. Any other way is just guesswork.

Is that in the same way that I've heard of some manufacturers, like Demon carbs, describe flow rates as 'wet'?

Yeah that is to take into account the change in flow due to the density and mass increase from where the fuel is added to the airflow. However I don't know which way this effects flow ratings.

Dave,
I just whant to try this out as no one out there seems to have done this to the BG carbs and al say they wount flow as mutch as my stoker needs so im simply going to try to do the venturis on the outer carbs on the BG the same zice as the Holley´s but the center carbs will stay the same and it is already bigger than the Holley so something must come out of this but will it be crap or good i dont know but hopefully i will be abel to tell the tale so to speak ! I also whas lucky to find a set of NOS Direct Connetion mecanical Holley 82&83 carbs but i dont dare to try those at this time however if anyone out there can help me out whit the corekt linkage for those carbs pleas let me know.

Very interested in hearing what results you get.

The mechanical Holley six pack you have there I have only seen over here once before.
Many years ago it was on this car here;
http://www.ebay.co.uk/itm/72-Plymouth-C ... 2c774fce52

But from the description in the ad it has been removed at some point.

http://victorylibrary.com/mopar/log-2.htm has some tips on constructing a linkage.

The mechanical set-up on mine was a "Six Packs to Go" conversion. The centre carb opened 50% on a sliding rod before the outer carbs started to open. All three fully open at the same time. There will be some photos of the linkage somewhere on here.

Thanks Dave

I do understan how the linkage is surpose to work and shore i can make a nice set my self but i would prefere the one that came whit the carbs over the counter at the local mopar dealer if it´s possibel but these carbs are hard to find in this conditon thoe i have to take them apart if i ever diside to use them !

Pleas bare whit me on the updates on the BG carbs becas i will not be abel to get in the machines at work before xxmas holliday as i plan to do that then when the shop is closed but Abe i will continue i promis It would be great if i could get them to work properly and prove to some that it is possibel to make a difference in realety and not just have lots of negative opinion´s behind a computer (no offence to any one on this board) but if i fale i can always drop back the vacume once again as i wount sell them.

Result on these new Holley parts and centre carb, got the lot for just 150 quid

Ade that sounds like a great deal =) Always good to have some spare parts to !

Grab it while you can eh? Buying that lot new would be 4 times that, easy
If you get stuck for any bits of linkage Pat, have a look at that pic and if there's anything there you need I'll post it to you

Im doing some inprovement now at work on the carbs bodys ! The first pic show bouth rigged in the spark machine and it is on its way down the first venturi but it is a bit blury pic becas there is fluid in the container !

The second pic show´s one carb body and the right venturi you can see that the electrode has taken some
but there is more before im compleatly down so this is just to see what im doing to them now and there will be more pic later showing the finisht results and some other inprovents i will do but for now im just doing the venturis larger.

Exactly how much are you taking them out to Pat? Is it just a few millimetres?

Ade it is mm in the opening area and 0 at the throttel blade opening so the venturi will be more strait like the Holley ! The way im doing this in a spark machine is very time consuming but the venturis will be extremly alike in al 4 corners and way more than a cast carb body as the cast moves around alot when it cools down. The center carbs is bigger than the Holley center and my hope is that that alone will inprove alot but whe will see if this will work or if it will be a sacrifice to the speed gods

Now im almost ready whit the carbs ! I have milled of the choke towers on al 3 carbs to make them flow as mutch as they can at that end and the venturis on the outer carbs are done so im just going to take of the sharp edges after the milling on the choke tower and then flow test them to see what it realy did on the flow !

Lookin good Pat
Did you flow test the same carbs before you started the machine work or are you gonna compare them to factory figures?

Ade i dident toutch the center carb and it is the same carb body as the outboard that i enlarged so i will compare the center to the outboard and i will also flow test one Holley outboard mostly to see what that one
realy flow in same betch ! I will flow test late tomorow so i gues i have the result in two days here !

There are some guy´s out here that say the BG six pack carbs flow whay less than the Holley`s but i whas surpriced today when i got the chans to flow test them at a well known head porting guy that have a flow bentch.

Whe started out whit flow testing a brand new out of the box Holley outboard carbs that Holley say 500cfm and it flowed 532,6 cfm

And a out of the box BG that whas stated at 355 cfm flowed 510,5 cfm at same underpresiure so i almost dropt my face

There is no way these are as smal as some say only about good for a 383 engine

If you consider al 3 carbs flow above 510 out of the box and compare that to a Holley set whit that smal center carb i would be very supriced if there not at least almost equal whit al 3 carbs on full throttel

The only modification i did on the center BG carbs whas that i milled of the choke tower and that cant make sutch a big difference !?

I have to take of some sharp edges in the outer carbs venturis that i dident think would do any difference but i whas terrebly wrong about that becas they only flowed 495 so the guy showed me how to do it right and just smothed out the edges some (NOT AT AL MUTCH) but then it jumpt up to 517,5 so i gues that i will make them flow more after al but how mutch i dont know yet but bare whit me Ade i will come back and tell the tale and where are also going to compare the jet signal on the modifyed outer carbs to the un toutcht center carb !

That's turned out to be a big difference in what you measured and what the BG carbs are rated at, but is that cos BG flow test 'wet' and the Holley are tested 'dry'?
Still definitely worth milling off the choke horns tho eh?
Keep at it Pat

Remember what I said a while back?

dave-r wrote:You can't go just by size. A smaller opening can flow just as well as a larger one. The air can just flow faster in the restriction which improves signal strength and mixture quality.

The ONLY way to know for sure is to use a flow bench. Any other way is just guesswork.

Adrian Worman wrote:That's turned out to be a big difference in what you measured and what the BG carbs are rated at, but is that cos BG flow test 'wet' and the Holley are tested 'dry'?
Still definitely worth milling off the choke horns tho eh?
Keep at it Pat

Ade yes it must defenetly be that BG is rated wet and Holley must be dry becas my dry test tell the tale !

No i dont beleve the choke tower mill of make soutch a bif differens but since the free space to the
air cleaner lid if as it is on the stock air cleaner it should be a good benefit on the flow when the
air cleaner on but im no expert on the subject yet.

But im still glad i whas curius and dared to try to make the outer carbs biger on the venturi becas i would be surpiced if i cant make them flow as moutch as the Holley outer carbs when im done.

Today i smothed out the sharp edges around the venturis and the outer carbs now flow 527 on the rear carbs and front flow 525.8 and i will have to leave them like that so that´s about only 6-7 cfm from the Holley outboard carbs and about 16-17 gain per carb in flow from out of the box and have in mind that i straitend the venturis to same status as the Holleys but the throttel opening on the BG´S is about 1,4mm less that the Holleys and whit the total flow numbers of about 1562,8 in total on the Barry Grant set at the moment and i doubt that the Holleys will flow that moutch whit soutch a smal center carb so i gues i made my goal on the flow !? But now i dont know yet if i have knock of the ballance on the fuel curve to mutch or if i can jet my way back and that will have to be done in spring i gues

Well you achieved your goal of increasing flow with some solid success so I guess it's just a case of seein what affect it has on the motor and how much tuning is involved.
Like you say it must have some effect on signal strength but how much we'll have to wait and see eh?
Ta for takin the time to go thru it and post it up

Sorry that everything is taking so long but i have had some time to spend on the carbs trying to put them back together and what i dident like whas the fuel level valves as they were REALY sticky but i whas already thinking of buying big flow once so i did and have them almost ready to put on the intake.... Just need 2 new pump nozzels for the outer carbs becas they also dident pass my qalety inspection =) Realy bad directed
holes in them on passenger side so i orderd new Holley insted. Will post more later whit pic !

Are the BG squirters badly machined? I would have expected them to be pretty accurate.
Are you going to experiment with different nozzle sizes Pat?

Hi Ade Yes the squirters hole were badly located for the passenger side ! I will run the center carb whit a bit bigger squirter 35 and the outer carbs will be 32. The main jets out of the box on these carbs are 68 in al of them but that will be to smal on the outer carbs for my stroker so i changed to larger in the outer carbs. Ade if your going to run your stroker whit a six pack stock setup like i have done for 2 year you will have to calulate whit a bigger acc pump on the center carb 50cc and change the squirter to 35-38 zise and larger main jets will also be needed and a set of Pro Max billet main jet blocks for the outer carbs will make your engine smile but i cant say i had any luck whit the center main block that Pro Max sells on my early 440 six pack engine so i stayed whit the stock block on the center carb and it works perfect.

Now im on the way and fighting whit fitting of al components around the carbs and of corse the among al i need to do a new air cleaner

Pat that looks wicked

Nice work Pat!

Thanks Guy´s ! Im gona try to make a new air cleaner whit the KN filter that is for Ford becas its not that wide but i dont like Ford mutch other than the filter Il keap you updated whit more pic later if i make any progress. How are you comeing along whit yours ? Id realy like some motivations !!!!!!!!!!!!!!!!!