How to measure converter clearance to engine / adapter plates.

First off, install the converter into the housing. on a Th350/Th400 you will install the torque to where you feel it click in three times and it spins freely. if it does not spin freely when it is fully seated in the tranny, you got a problem.

Next, lay a straightedge across the face of the bellhousing (engine side). I usually use a large carpenter’s square. With the converter installed in the transmission, take a ruler and measure the distance from the straight edge down to the mounting pad of the converter. The measurement should be as follows:
GM TH-350: 1 1/8″ from bellhousing to mounting pads
GM TH-400: 1 3/16″ from bellhousing to mounting pads
GM Powerglide: 1 1/8″ from bellhousing to mounting pads
Ford C-6: 1 1/8″ from bellhousing to mounting pads
Chrysler Torqueflite 727: 1 1/4″ from bellhousing to ring gear
Note: Distance may vary either way .050″.

when using a stock replacement converter, tranny, and engine there is usually no need to worry about this.

With the transmission installed to the engine ,you should have between 1/8″ to 3/16″ of clearance between the torque converter and flexplate before pulling the converter forward and bolting it to the flexplate. So, when using an adapter plate/distributor protector, you can use this as a guide to select the right thickness of shims to properly set your converter to not bind the engine, housing, or most of all the pump gears into the back face of the pump. for derby i like to lean more toward 3/16″ as the converter needs as much room room to expand as possible as it heats up quickly. It may seem like if isn’t in the pump that far but trust me, as it gets hot it will be in there just right.

commonly an adapter plate comes with shims of the correct thickness and these measurements become somewhat pointless when using a factory converter on a factory tranny. However, when you mix and match aftermarket performance converters it can be an issue. the only time i had a real problem with one though is when using a powerglide core custom built with a turbo spline installed in a th400.

also when using washers from the hardware store as converter shims you gotta be careful. most of the cheap washers like that don’t have identical thickness and can really screw things up. you are usually better off cutting shims from the same material as the adapter plate. you should also be aware of how the snout of the converter centers in the end of the crankshaft. some of these ungodly thick adapter plates i have seen can pull the converter out of the end of the crank and the converter never centers- causing a lot of problems and vibration.

Comments are closed.