I just purchased a Carter 1bbl carb to use with my original carb (a Carter BBS2985S) on an Offy dual intake. The seller, who appears reputable, said that the carb was a rebuild for a 60-61 Slant (2985S/2986S-3098S/3099S). Everything looks identical on the "new" carb except for the fast idle cam. The cam on the "new" carb has a deep cutout or drop-off after the step-downs, the cam on my original carb does not have this cut-out.
What kind of problem is this going to cause? Am I going to have to locate, or possibly fabricate, a new fast idle cam?

Thanks for any and all input.

Bill
60 Dart Pioneer 2D Sedan
Slant 6 A/T

The original carb you're working with has only a single idle speed adjustment screw. This caused no end of problems in '60, because it was nearly impossible to get both the fast and curb idle speeds adjusted correctly. For '61, the fast idle cam hold-down screw's head was greatly enlarged (made thicker), the bottom part of the fast idle cam ramp was clearanced so the fast idle speed screw wouldn't touch the cam at all when on curb idle, and a second (curb/hot/slow) idle screw was added, aft of the fast idle screw, to bear on the enlarged cam fixing screw's head.

Using one of each is going to make it tough to synchronise the carbs...and those '60-'63 carbs are tough to adapt to the dual-carb setup in the first place, due to the integral choke air bleed. You've got a task on your hand if you're bound and determined to use those carbs.

But yeah, the jetting'll match!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

In warm weather areas, I have successfully run the dual carb set-up with one of the 2 carbs having a working choke, or with no chokes at all.
As noted, you will have some issues with cold engine settings but once hot, things should work fine.
DD

Thanks again Dan, I see what you are describing...and thanks Doc.

Unfortunately, I live in Northern Illinois. Winters are fairly mild (temps in the 20's) with an occassional cold snap. I don't plan on driving the car in the winter, but would like to start it up and get it warm once in a while until spring.

I am planning on fabricating a choke linkage to tie both carbs to a modified automatic choke. With this and the Offy linkage, can I control one carb with the other? Will this help the situation?

I have already considered the possibility of fabricating a matching fast idle cam.

Should I continue being a glutton for punishment, or should I just look for two identical post '63 carbs?

Thanks again!

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Bill

'60 Dodge Dart Pioneer

Vivian

You can rely on just the one carb for fast and curb idle speed regulation, but it will be very difficult to get satisfactory carb synchronisation that way, so idle and low-speed running quality may suffer. Remember, the final step in tuning this setup is to disconnect the linkage that connects the two carbs and set each carb independently. Even the best linkage has some free travel in it...typically what happens when trying to use the throttle stop screws of one carb to regulate both carbs is you get the carbs synchronised, but then you operate the throttle, both carbs open and close...

...and you find them out of synch.

Another '61-'63 carb or a set of later items would probably work better for you, but there's less expense involved in trying out what you've already got and seeing if you can make it work satisfactorily. Carb swaps are easy.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

also for a choke setup, I got some info from Dan on an electronic choke and an old diagram for fabbing up a dual carb choke. Haven't done it yet, but plan to
MJ

I spent a couple hours this weekend removing the stock intake/exhaust on the 225 on my 68 Dart GT, installed headers and an offy dual single intake and 2 Carter BBS's. Bought the carbs before I realized the linkage that came with the intake was built for Holley's, so I'm working on some fabricated linkage to maintain the kickdown geometry and throttle cable positioning.

That part is going ok so far simply by re-hanging the cable/kickdown bracket 2" below the intake using the available mounting holes and some spacers on the intake. Fabricating the throttle linkage looks do-able also with a couple bell cranks and brackets, but I'm interested in your ideas also if you are willing to share. Also your choke diagram if you still have it, haven't even looked at that yet (I'm up north also, but in NY, so I'll have to deal with that eventually).

My problem right now is with an idle at 1500 RPM that won't drop below that. I checked the fast idle screw is off the choke cam (choke is open) and the low idle screw is off its stop. It acts like the butterflies are stuck open a bit but they look ok (next step is to remove the carb and recheck). It doesn't seem to be running on the normal idle circuit because I can screw the mixture screws in all the way with no effect.

I haven't messed with the insides (jetting) as these carbs were bought new/rebuilt at Carlisle this summer (one looks NOS, the other rebuilt).

Any ideas what to check to bring my idle down to the normal 600 RPM? I'm not a carb expert by any means, but able to rebuild if necessary, but would like to rule out something dumb I did first. Suggestions welcome.

Thanks, Mike

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Mike Allen - 68 Dart GT

does your carbs has a calibrated vacuum leak near the throttle blade? our factory equipped 2x 1bbl cars had a 1.35 mm hole on the base of each carb, slanted so hole would start at the outside base of the carb and extend to below the throttle blade on the inside.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

It's not that the linkage was intended for Holleys. Holley 1920 and Carter BBS carbs use the same linkage. It's that the manifold and linkage were designed for use on '60-'66 cars with the rotating-rod throttle control, and you are putting it on a car with cable throttle control. So yeah, some fabrication will be necessary. The fast-idle problem is probably down to one of the carbs being improperly assembled (throttle plate not centred correctly on throttle shaft) or a linkage problem that holds one or both of the throttles slightly open. Try disconnecting the interconnect link and see if you can get it to idle down.

It is absolutely critical that carbs used on this manifold be exactly matched. The "one new and one rebuilt" makes the hair on the back of my neck stand up...I hope you can make them work.

The calibrated vacuum leak Argentina_Slantsixer talks about is present on some but not all of these carburetors. It's there to assist with smooth transition in the power circuit and to help trim the vacuum advance kick-in. However, I haven't seen the type he describes, leading to below the closed throttle plate -- only ever well above it. It's possible the Argentinian-market carbs are configured differently. In any event, this isn't causing your problem.

One additional question: How is your PCV valve plumbed in?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I'll have to remove the carb and check in the am. I seem to recall one of the two carbs may have this. The carbs are identical in the top and center castings, but the base plate on one is different from the other (it has an extra vacuum port that I plugged). I thought I had checked and plugged the nipple on this, but maybe its not what I thought it was.

On that same track, I'm running the PCV and vaccuum advance off of one carb, and plugged the other....is that the right approach or should I be using a "T" and connecting to both?

Thanks for the baseplate idea.

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Mike Allen - 68 Dart GT

I'm wondering the same thing about the rebuilt one not being assembled correctly, so my next step was to disassemble that one....its the same one that's not pumping correctly when the plunger is pushed (and the same one that might be sporting the vacuum leak). A vacuum leak was my first guess but didn't find one. It is flowing fuel however, the headers get hot and the plugs looked ok (but obviously not flowing it right).

I'll pull that carb tommorrow and take a look.

Are rebuild kits for these BBS's readily available? I've had a spare one apart before just to see what was inside but didn't actually rebuild it.

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Mike Allen - 68 Dart GT

Its plumbed to one carb, not both...the other is plugged....should it be split between the two? what about the vacuum advance, same approach?

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Mike Allen - 68 Dart GT

There's a threaded tap in the crossover passage that runs between the two carbs. Install an appropriately-sized vacuum nipple in that threaded tap and run your PCV hose there. Plug the PCV port on both carbs. Vacuum advance...my tendency is to build a "tree" out of short lengths of vacuum hose and a Wye fitting, connect to both carbs' vacuum advance ports, and run the single resultant hose to the distributor.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

ditto

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

I have a picture of what you're looking for here: Offy Setup