Retro-fitting modern, overdrive transmissions into early musclecars is nothing new, and with the rapid raise in gas prices (only two dollars a gallon as this is being written) the trend is sure to grow. The most popular swaps continue to be the 700R4 and the 200R4, both of which are good choices and have their advantages. The physical swaps are straightforward, but the one component that still mystifies many people is the throttle-valve (T.V.) cable setup. If the T.V. cable is not set correctly, the transmission can operate poorly, and its life can be greatly shortened. When connected to the throttle linkage mechanism, a correctly set up T.V. system will pull the cable, causing the part throttle/detent valve inside the transmission to immediately start moving with even slight carburetor-linkage movement.
Designing a pulling arm on your carburetor's linkage that pulls the T.V. cable this fixed distance is the easy part. The challenge really begins when you want the transmission to behave in a specific manner. The physical dynamics of this cable pull can vary radically with different pulling-arm designs which control the rate of plunger travel speed just off idle and determine the shift timing and shift feel of the transmission.
Bow Tie Overdrives has just released a quick, easy, and very precise throttle valve control system for correctly setting up this relationship in minutes, not hours, and allows a wide range of adjustments for fine tuning the transmission's shift timing and shift feel. The system is available for Edelbrock Performer series, Carter AFB, Demon and Holley 4100 series carburetors.
We started by removing the carburetor and gaskets and cleaning the intake surface. We then installed the supplied open-bore gasket and the new, square-bore base plate with the four, small, threaded holes positioned to the driver's side rear. The gasket with the four throttle-bore holes was next.
The new T.V. cable-mounting bracket was then bolted over the four holes in the base plate using the four 10/32-inch pan head bolts (Do not install any spacers between the base plate and the cable-mounting bracket). The new T.V. cable to the transmission was attached, routed up to the carburetor, and snapped into the T.V. cable-mounting bracket.
While the carburetor was off the engine, we installed the new linkage adapter. We pre-assembled the three-piece adapter to see how it went together. It will sandwich over the carburetor's stock linkage, indexing over the lower, stock cable-attachment hole with the raised lip.
We used the adapters front plate as a drill guide and drilled a hole approximately half the way through the carburetor's linkage with the supplied .144-inch (#27) drill bit. (Note: We didn't drill all of the way through the carburetor linkage at this time because it would have damaged the back plate's threads.)
The three-piece stack was placed over the stock, raised-lip, kick-down stud location and to the linkage using two 6/32-inch pan head bolts through the two unobstructed holes in the adapter stack. Only two of the three 6/32 pan-head bolts can be installed because the carburetor's linkage prevents installing the pan head bolt in the upper left hole. A hole needed to be drilled through the carburetor's linkage to allow the third pan-head bolt to be installed.