Need proof of how the 5/16 inch holes in a GM-style mechanical clutch linkage distort over time? Check out the holes in this old linkage.

The fix for distorted holes is pretty simple—drill them out to 3/8-inch using a sharp drill bit. This allows the use of 3/8-inch rod ends.

You’ll have to do the same thing to the pair of holes on the Z-bar. The bolts we’re using have a 3/8 inch inch fine thread.

Many clutch pushrod setups have a pointed or semi-ball end on the clutch fork side. To make one, cut the head off a 3/8 inch fine thread bolt and grind the end to a shape that matches the fork. I put the bolt into an electric drill motor, which allowed me to grind the piece on a stone and a piece of coarse sandpaper to get a nice radius.

I used 5/8-inch OD chromoly tubing to build the linkage. To make this work with a 3/8-inch rod end bolt, I used some thin-wall (0.058-inch) tubing and 3/8-24 to 5/8-inch x 0.058-inch wall tubing adapters. Here’s how I made the push rods. I measured the stock push rods to get the proper overall length as shown. Then I cut the tubing to length, taking into account the length of each tubing adapter, along with approximately half the threads of a rod end for each side. The tubing adapters I used measure just under 7/8-inch each when pressed into the tube. Other adapters may be slightly shorter or longer.

To cut a piece of 5/8-inch, 0.058-inch wall chromoly to size, you can use a hacksaw butted up against a hose clamp at the cut line, or use a big tubing cutter as shown here. With either method, you’ll have to deburr the inside diameter of the tubing. A fine tooth round file is perfect for the job.

The ends of the tubing for the short pushrod were filed down and a pair of Mark Williams tube adapters was pressed into place. One side has left hand threads while the other has right hand threads. Repeat the process on the longer pushrod and weld the tubing adapters in place.

I used high quality, three-piece aircraft style 3/8-inch rod ends. You can use cheaper pieces, but it’s best to stick to top brands like FK Rod Ends, QA1, and AFCO Racing, all available at Summit Racing.

Another alternative to building your own linkage is to have it made by a competent chassis shop. Here is the linkage I had Jerry Bickel Race Cars make for another project. The biggest difference between this linkage and the linkage I built is the large adjusting nut on the Bickel parts. It allows me to adjust the clutch with an open end wrench instead of having to drop the entire linkage assembly.

Here’s a direct comparison of stock linkage from a 1969 Camaro with a Jerry Bickel linkage. It’s a wonder the OEM stuff lasted as long as it did behind all the horsepower we made back in the day. It sure wouldn’t hold up behind today’s 800 to 1,000 horsepower “street” engines!