I figured out a repair for my cam

[rich]

I have a neighbor that owns a medium to large machine shop. I am going to have him rifle drill my cam about 1/2" into the bolt hole. The hole will be just smaller that the broken stub. Then I will have them thread the hole.
Then I'm going to have him make a new stub that will thread in. I will use red locktite to install it and make sure the threads will always be pulled in the tightening direction as it rotates.

[rich]

Here's the cam.

[Blau 5speed]

Rich,
Now I don't claim to be an engineer or a machinist, but I don't believe the repair your propose will last. What diameter do you plan to make the threaded portion of the new stub? My concern is that any workable size will be a much, much smaller diameter load member under lots of stress. Plus you have the shoulder area of the cam to machine that is probably full of stress cracks... I don't know. If it was me, I believe I would be looking for a replacement cam.

Best of luck though.

Bill

[rich]

The outside diameter of the stub is 23mm. The outside diameter of the cam at the front bearing surface is just under 30mm. The wall thickness after drilling a hole through the new stub for the sprocket bolt is 6mm.

My cylinder walls in my block are thinner than 6mm and under way more stress. It looks like these cams break because they are cast. A steel billet would never do this.

I was thinking my repair idea may even work better if I did the same repair only cut the cam off at the flange at the rear of the bearing support. Then drill and thread a repair section onto the cam at the flange. The threaded section then wouldn't be hollow. The repair stress would be supported by the bearing rather than hanging off the end of the cam.

These cams are only surface hardened. The center is drillable and tapable

[Danglerb]

Threaded I can't see working, but drill a hole and make a new end that slips down into it and gets "bonded", maybe via soldering or brazing "might" work. The angle needs to be accurate within a few degrees doesn't it?

OTOH any pair of good 16v cams will allow the engine to run decently well. Euro parts are only pricey when you don't want to wait a few months for a cheap source, they will eventually show up.

Cam breaks and that would kinda suck?

[rich]

Originally Posted by Danglerb

Threaded I can't see working, but drill a hole and make a new end that slips down into it and gets "bonded", maybe via soldering or brazing "might" work. The angle needs to be accurate within a few degrees doesn't it?

OTOH any pair of good 16v cams will allow the engine to run decently well. Euro parts are only pricey when you don't want to wait a few months for a cheap source, they will eventually show up.

Cam breaks and that would kinda suck?

Ya, I have two engines here to prove how much it sux.

Are you online? I pm'ed you my phone number. I have a question.

[Danglerb]

<<<<<<<<<<<<<<<<---------- Green dot means I am in the forum "recently".

PMed you my number if you still need help.

[rich]

Originally Posted by Danglerb

<<<<<<<<<<<<<<<<---------- Green dot means I am in the forum "recently".

PMed you my number if you still need help.

Thanks, Got it.

I was at the lake all day dropping trees and loading wood. I'm fricken dead.

[mistertate]

Even if it doesn't work it's an interesting idea. I think in some ways its going to work like a 'cracked' or 'fractured' rod if you've ever seen those. On cracked rods the interface between the two parts is rough like your broken cam and allows the use of a smaller rod bolt because of the peaks and valleys of the fracture resisting shear forces. So as long as the bolt you use has enough tensile force to keep the fractured ends together tight then the fractured ends will resist the torsional forces. It might be fun to do some napkin calculations to see if it will work...

[Danglerb]

The failure mode was too much tension on the cam gear, which snapped off the nose. A bolt and the rough surface might be ok for torsional forces, but it won't do squat against angular forces.

If this was flight of the Phoenix I could see fixing the cam, but other "good" options are out there for such a critical part.

[rich]

I've had a number of my friends caution against any type of repair. I guess it's the reverse engineer in in me. I'm always looking for the fix.

BTW: The first version of Flight of the Phoenix is one of my all time fav movies. During the filming a guy was killed flying a plane that looked like the one they were building in the desert. I'm all about that movie.