Carter RBS adjustment.

[60s Refugee]

Hi all,

Friend of mine just got a 1971 Mustang with a 250 CID RBS Carter carb set up. His idle is too high. Before I screw it up for him I thought I'd ask you all about how to reset it!

Harry

 

[CZLN6]

Howdy Back Harry:

There are two adjustments that effect idle on an RBS. The first is the curb idle, which is the effective one after the engine is completely warmed up and the automatic choke fast idle no longer has effect. It is a slotted screw head just to the rigne of the distributor vacuum nipple.

The other screw that effects idle is the fast idle setting screw. It is only in effect when the choke is not fully open. Or, whe the choke or linkage is sticking. This screw is located almost directly opposite of the curb idle screw. it has a tensions spring on it's collar.

Ist, verify that the choke is opening properly and fully. If not spray it down with carb cleaner and/or reset the spring cap so that the choke opens fully once the engine is warm. That should be about 7 to 10 minutes after cold startup.

2nd, Once that is done set the curb idle screw, Is this an auto trans or manual car. If auto set the curb idle with the car in drive and with the brake on.

The only other adjustment is the low speed air screw which is located near the base of the carb next to the fuel bowl. It can effect idle and off idle transition. Adjust it to achieve the highest idle rpm. It the idle increases, be sure to lower the idle speed again.

All other adjustments are internal and may not be necessary if this carb is still on its original engine.

Is this an auto trans car? Give me some feedback, please.

adios, David

 

[60s Refugee]

It's an automatic. I looked it the carb and noticed a dash pot looking thing with a wire running to it. There was a hex head on the plunger and I wondered if that might be the problem. It seems to be preventing the linkage from returning to idle.

Harry

 

[CZLN6]

Howdy Back Harry:

Yup, that's the 3rd adjustment. To adjust, turn the dashpot or the set out/away from the idle stop. IIRC both are threaded and either can be used to adjust the point of engagement of the dashpot. Once there is clearance, finish adjusting the curb idle stop, the fast idle setting, and the low speed air screw setting. When you're satisfied with all of these, adjust the dashpots point of engagement.

The dashpost is designed to slow the rate of deceleration of the engine rpm with a vacuum canister. This is only an issue on engines with an automatic trans. These engines have a dendency to die when coming to a stop in traffic. If yours has a wire to it it may also have a solenoid activation. Either is adjusted with the same procedure. About the only adjustment is the point of activation. The farther out/sooner it makes contact with the linkage the sooner it slows the rate of deceleration. Farther in/away from the linkage it begins to function at a lower rpm. Once contact is made with it the rate of deceleration will be the same.

Personally, I like a quick rate of deceleration and have had little or no contact with the dashpot. With an auto trans, you will have to set the curb idle about 200 rpms faster than with a standard trans anyway. Which may be enough to keep the engine from killing when coming to a stop.

Let me know how it works out.

Adios, David