How to fix 1150 valve cover towers (if you want to hold high mass)

[Greg B]

Have you ever bought a bike, and once you had to open it up you found things that made you say "Aw CRAP!"?
Here's what I went through. Kind of a PIA but hey, whadda ya want.

You can see the small crack. While not bad, doesn't give one the warm fuzzies. So, I made a fixture to mount in the lathe and get the hole running true.

Machining the register. Just wanted a true diameter. Size wasn't important.

Once that was done I turned a collar that was about a .001" slip fit on the register I had just machined.

Collar installed with some Loctite RC680. That ought to keep it in place.

[Greg B]

Oh, it gets worse. On to the second tower.

This one won't be so easy.

Using the same fixture, I bored and threaded what was left of the original hole. Being careful not to machine any deeper than the depth of original hole. Breaking into the cam journal is BAD.

Next, a threaded insert to screw in place. I also threaded the "tower" portion, because I intend to (in belt and suspenders fashion) slather JB Weld over it to (hopefully) make the repair as strong as possible.

Insert Loctited into place. Will finish it up tomorrow, after everything cures.

[rapidray]

THIS is why Greg is my friend! This is also why I help him with his motors & have HIM make special stuff for me! GREAT job pal! Ray.

[Greg B]

Finishing everything up.

Cam cap back in the lathe, faced to length, drilled and tapped. You can see how I coated the part with JB.

Ta Da.

I needed to machine clearance for the cap bolt since the epoxy had oozed.

[Greg B]

And there you have it. Two repaired towers. I realize not everyone has a shop in the garage. But I hope some folks enjoyed this.
Greg B.

[exhondaguy]

That's a really good fix!
How do they get so broken though?

[Greg B]

I suspect the previous owner was removing the valve cover and forgot to take one of the cover bolts out.
The tower with the crack looks like the bolt was overtightened.

[Nessism]

Impressive work Greg. You obviously have some significant skills.

[p_s]

Nice. How did you make the fixture that holds the bearing caps in the lathe?

[cbxchris]

I've had them so bad that I have had to rob a tower off a ruined head. Its amazing at how many will work. I either use a air gauge or plasti gauge to check them for clearance.

Nice work! If I'm not mistaken isn't that a 7mm bolt in those towers? I had a heck of a time getting heli coils for them.

[Greg B]

The "fixture" is really nothing more than a slug of aluminum bar I had. Faced in the lathe so it was dead perpindicular to the lathe axis. My chuck has a threaded back plate so I can unscrew the chuck without taking the slug out and it remains in the same orientation when I put the chuck back on. As you can see, I switched over to a collet to make the other parts.
I held a pin in the tailstock to roughly locate the cam cap. Then I marked the mounting hole in the slug. Drilled and tapped for 10-24 button head screws. That way I had plenty of clearance to indicate the cap.

I have two other 1150 heads but If I had scavenged caps from them I would need to come up with other caps when I got around to building those motors.
You can get 7X1mm Helicoils from McMaster Carr. I recommend you get the proper installation tool, the one that compresses the insert during installation.
I ended up buying a 7X1mm tap, again from McMaster. I have the Helicoil kit, but wanted to just tap the tower directly to keep the material as thick as possible. There is enough meat to Helicoil it later if necessary.