matv91, why do you feel there is such a large difference in CFM rating as per Carter carb specs?

You pointed out the major difference between the carbs is the venturi cluster screw.

1978 slant Dodge truck flowing 285 CFM and the cars 220 CFM.

How is this CFM rating figured out and what does it mean to a carb user. I understand it is a rating of air flow I.E cubic feet per minute ( I think ) but I dont understand what that actually means for driveability.

!930, the information provided by matv91 is exactly the same as I linked to in the beginning of this thread, the only difference is that in my link, the 3 manuals have been assembled into one manual. All the text that matv91 kindly reproduced for you here, is from those manuals. You should definitely try to read them, and - as matv91 has done - compare the numbers in the parts lists, as I told you.

As I wrote in the PM, there is no way you can tell if your carburetors have been modified since they were new, some 30-35 years ago. They can be assembled from parts from several BBDs, and the tags can be from any carb! Regarding all parts that doesn't have a number imprinted on them; unless you have new spare parts in their original, numbered packs, and can measure them and compare them to your old carburetor parts to confirm the identity, there is unfortunately no way you can build an exact clone of the old carburetor.

Another thing is the state of the BBD housing: Is the throttle shaft leaking air? Are your air horns bent like mine are, from hundreds of air filter removals and reattachments with an overtightened wing nut on the lid, making all adjustments that includes clearence to the choke throttle blade a nightmare? Are you jets and metering rods worn? Is there corrosion or deposits in the fuel passages? Is the bottom plate warped from thousands of heating/cooling cycles?

As I told you in the PM, the recipes for carb adjustments provided by other members in the forum, is based on their practical experiences with the BBD over decades! But, no two engines are alike, and unless your engine is bone stock, tight and new, and can only run perfect with a new original BBD, it doesn't matter which carburetor you put on the engine!
That is perhaps the single most important piece of information you have been given here.

You have to be able to adapt and tweak the BBD to your engine's and drive line's current condition, as well as your own driving habits, to make it work as intended, no matter which carb you use.

Olaf

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Aspenized

That is on my list of to-dos, I am also trying to find the time to read 392 pages of posts on this forum, 81 pages of posts on the for A bodies only forum, various books/literature/information that has been given/sent to me as well, all of this and still try and support a family by going to work long hours.

Not trying to make excuses or to have someone do for me what I need to be doing.

I would guess that matv91 has read those many pages before and specifically knew where within the pages that information was located......I did open the links and look thru the pages briefly, I could have spent multiple days scouring ( cause I typically do not have a few hours at any one time ) and then prob still would not have been clear on what I was looking at so it was a big help to have the specifics given to me, it will help my slant get back on the road that much faster.


Quote: there is no way you can tell if your carburetors have been modified since they were new, some 30-35 years ago. They can be assembled from parts from several BBDs, and the tags can be from any carb! Regarding all parts that doesn't have a number imprinted on them; unless you have new spare parts in their original, numbered packs, and can measure them and compare them to your old carburetor parts to confirm the identity, there is unfortunately no way you can build an exact clone of the old carburetor............

I understand and agree with this. I wont throw my hands up in the air however and just say its no use. I would rather educate myself on how they would have been originally set-up and the adapt to what problems I have to deal with.


Quote: Is the throttle shaft leaking air?...............I do not know how much play is too much play, I have read posts already that have asked this question and it seems by the replies that its sorta a call that cant be made over the internet.

I have one carb that does have a bit of play, not bad at all compared to some of the 1945 carbs I have collected and fiddled with.

The other BBD is super tight, so tight that the throttle shaft is barely turning at this point ( from sittin, not from rust necessarily ) and so I dont know its condition. Ill either have to make one very nice one from two or have them both re-bushed. Havent made it that far yet.

Quote: no two engines are alike, and unless your engine is bone stock, tight and new, ........

It is a new re-build, tight like new but yes overbored 40thou and all othe necessary machine work done. Close still I would say to a new engine.

Quote: due to the differences in fuel today vs fuels of yesterday, experimenting with different combos may be very useful rather than try to mimick what chrysler did 30+ years ago..............

And it did not fall on deaf ears, again collecting information so I am educated on the subject to a certain degree.

Please do not feel as if I ignored your advice, that was not the case.

matv91, why do you feel there is such a large difference in CFM rating as per Carter carb specs?

Thats a typing error that was corrected in the 1979 version of that form. I have the paper one here it is not on the web.

D, W-1, 2, 3, B-2, 3 (Non-Calif.) ALL/T 225 285 8176S 902-325
That carb no 8176 was a different carb from the rest of them.Main jet 120-192 .092 much bigger than the others .086. Venturi cover assembly 118-335s different was used on some of the v8 carbs. And metering rod 75-2203 .071x.057. This metering rod was often used with the venturi cover 118-335s. Guess work, that 8176 was v8 carb set up for slant six. It would flow 285 cfm. Also note thats the only carb for the bigger trucks.

How is this CFM rating figured out. There are others on here that know more about that than me.

Someone on another forum was kind enough to share the specific FSM manual pages for the re-build of this particular version of BBD.

If anyone is interested I would be happy to post the pages here?

but I dont understand what that actually means for driveability.If the amount of air flow is the same but you change to a smaller venturi size this forces the air to speed up. Faster air flow breaks the gas into smaller sizes that burn better,the smaller sizes do not drop out of air stream etc. For example back in the day a quick fix for old wore out 318s with driveability problems was to put a smaller venturi slant six carb on it. Worked every time. Also worked the other way. Slants than seemed to have sags etc, some times the fix was to pull that v8 carb off.

1930, I hope I don't steal the thread with a related question:

matv91, do you know from your material if the later factory replacement BBD was narroved down to a single specification carb, or did mother Mopar provide several to choose from? If it eventually boiled down to a single BBD to cover all previous versions, do you have any number and specifications for that one?

If I remember and interpreted earlier post in the forum correctly, the later Holley replacement carb came in only one configuration, covering both SL6 and 318 engines.

Olaf

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Aspenized

Great question, I have some others as well that will be coming up.

information concerning how the carb was originally set-up internally? Id guess that info might be found in a factory service manual but at this point thats only a guess. The car service manual does not contain any info on carb internals. Only application numbers for example 8137s listed as federal and canda emissions 3500 pound class, 225 automatic, throttle bore 1-7/16, venturi 1-1/16. The service manuals were printed early in the model year so they do not have running production carb changes either. 8136s, 8137s,8217s,8177s,8218s are all slant carbs for 1978 .The service manual only list 3 of those numbers. Use the search in that pdf form any of those numbers should take you to right the correct page

8176S turns out this carb never produced. Can not find any after market mention of it.Not in carter after market book either.

Someone on another forum was kind enough to share the specific FSM manual pages for the re-build of this particular version of BBd . Yes like to see it.

1930, I hope I don't steal the thread with a related question:

matv91, do you know from your material if the later factory replacement BBD was narroved down to a single specification carb, or did mother Mopar provide several to choose from? If it eventually boiled down to a single BBD to cover all previous versions, do you have any number and specifications for that one?

If I remember and interpreted earlier post in the forum correctly, the later Holley replacement carb came in only one configuration, covering both SL6 and 318 engines.

Mopar would have got there replacement carbs from carter.!985 new carburetors book shows exact replacement numbers. So no . No one fits all. My holley book is from 1982. Carb 8691 shows for 1977 225 eng all trans. Carb 8870 for 1977 dodge truck 225 eng all trans after market replacement. Thats all i found. maybe after 1982 holley came up with other carbs.

Here is a link to that discussion. http://www.aspenandvolare.com/showthrea ... nual/page3

No sure if you can see the pics if you are not a member. If you cannot than just let me know, I can either post the pics here or send them to an e-mail, whichever you prefer.