Original 427 Street Cobra Suspension Rebuild

[David Kirkham]

Oh yes! Back to the bolts!

The bolts are 7/16 BSF--or British Standard Fine. If you look closely, you can see the bolts actually have a shoulder on them that fits down into the upright. The threads on the bolt are 55 degrees instead of the standard 60 degree threads that are universal today. I remember looking at the bolt under the optical comparator with Professor Kohkonen. We were perplexed by the 55 degree threads--until his face lit up and he said, "I bet those are Whitworth threads!" He was right. He convinced the Sandvik salesman to "donate" some 55 degree threading inserts to the university which Professor Kohkonen eventually gave to me for all the work I helped him with in the labs. I still have those inserts in the top drawer of my tool box! I remember making my first bolts out of 4130 chromoly. Chromoly was the buzz word then (and now). You wouldn't believe how many people think chromoly is made in heaven. It has SERIOUS drawbacks. I will get into that a little later. As I look back it wasn't the best choice for a number of reasons. Today I would make them from 17-4 PH H1150.

[David Kirkham]

Back to the rear Hub Bolt.

Here Sandwich has taken the bolt out.

[David Kirkham]

Here Sandwich has put a puller on the drive flange. The puller we use has a special tapered end on it which fits right into the hub--so we don't make those little divot marks in the rear hub bolt.

[David Kirkham]

Flange is now off and you can see the splines on the rear hub.

[David Kirkham]

Jim,

I have been posting like a fiend and I just went back to proof the thread and noticed you posted! Sorry I missed it.

I am going to show you the tricks we do to correct the original problems the car had. There are many little things you can do to make the car better and safer. I will show you some really ugly things coming up that NO ONE ever thinks of with these cars. I will discuss metallurgy and why we do what we do and why the original guys did what they did--complete with the advantages and disadvantages of both. It will be an interesting thread. I will move on to the front suspension when I am done with the rear suspension.

Stand by!

David

[David Kirkham]

Here is a picture of the drive flange that Sandwich just took off. It has to be taken off with a puller. I have seen a few of these come off without a puller and that is BAD!!! What happens is setting up the rear bearings on an original Cobra is a LOT of work. It is much easier if the drive flange does not have to be pressed on. You will understand why later when I show you what is inside of these hubs. Anyway, if the flange is pressed on, it helps to keep the entire system rigid so you are not entirely relying on the bolt to keep everything tight. If the flange can move, it will begin to "fret." Fretting is when two parts rub together and start to transfer metal from one surface to the other. The metal literally turns to powder as it grinds away. It is very BAD to have a flange move on a shaft. We use Loctite on loose ones when customers are dead set on keeping the original parts.

[David Kirkham]

Now the upright will simply pull away from the hub and rotor.

Notice the two shims that are still on the hub shaft...they smell like trouble. They always are trouble when you see bent hub washers like the washer above.