Case Saver Installation

Germaneighter · 10-07-2019, 01:41 PM

After (5) months I finally got some time to work on the case saver installation on my 1972 2.4 4R case. I had posted back in April about the quality of the case savers I received from Pelican (Case Saver Quality). I ended up purchasing some from the local VW guy to practice with. I sourced a junk VW mag case as my guinea pig. I have an older Rockwell mill that's in good condition I'm working with. I used a 12mm 3 flute end mill to help keep the hole centered over the existing M10 threaded hole. This was a dry cut with many chip cleaning stops because this is a blind hole. I threaded the 14 X 2 first using a tapered tap then switching to a bottom tap. (all mills & taps are new). I did both dry and lubricated tapping and think I like the dry tapping better. The case savers went in very easily until the last 1.5 mm due to the small, non-threaded top edge of the case saver. This last bit took a little more effort to make the case saver flush. My questions & concerns:
1.) while screwing the case saver into it's new hole I noticed it would rock back & forth just a small bit. That is until the non-threaded end hit the threads. I screwed an original head stud into the M10 threads of my 2.4 911 case and that too had a very small amount of rocking back & forth (but less than the case saver). Is this normal? Should I be using a slightly smaller diameter end mill?
2.) Should I be concerned about the small, non-threaded section that deforms the first thread(s) in the case when driven in flush? I used an EZ-Out to remove one of the practice case savers and there seems to be minimal thread damage.

In the actual install I'll be using Loctite.

Any advise/comments from those who have actually done this, or similar work, would be much appreciated.

Flat6pac · 10-07-2019, 03:09 PM

Seems like a lot of unnecessary work as there wasn’t a problem until the 2.7 with pulled studs because the factory used mag cases, steel studs, aluminum cylinders, and heat. 2 out of 4 made for self destruction.
Bruce

cmcfaul · cmcfaul's Garage

My 2.4 911 E 7R case pulled a head stud. replaced with case savers. Also stripped a thread where the trans mounts and installed one there. These old cases get brittle.

Chris

Germaneighter · 10-08-2019, 12:47 PM

Thanks Chris, this is what I've heard on the forum from numerous members.

I'd love to hear from anyone who has performed the work themselves.

thanks

r lane · 10-09-2019, 05:22 AM

I would at its age, thread the head bolt holes. I have a jig purchased in the 70's for just this job, but access to a mill is a better way. I generally lack scientific approach to most of what I attempt. I machined a pilot to slip fit the holes and set up on each one in that manner. There is a spec size drill or end mill for the insert so that it is crisp with no play. When running in the tap, I pilot it with a centering mandrel from the mill head. Most people seem to prefer the time certs, but in this application, I like the helicoils. Have never had a problem and the helicoil does not encroach on the cylinder spigot area as does the time cert. Bob

boosted79 · 10-12-2019, 05:46 AM

"Should I be using a slightly smaller diameter end mill?"

Yes. I've done a VW case and used a smaller tap drill than the tap chart recommends to get a nice tight fit. Mag is so soft you can get away with it.

Germaneighter · 10-14-2019, 11:33 AM

r lane
Thanks for the response. Since my mill does not have a DRO (yet) I machined a M10 bolt head & slightly center-drilled it on a lathe. Threaded into the original M10 head stud hole, I pick up the center using a ball end wiggler. Threading is done with the tap mounted in the mill (in a drill chuck) and turned manually with a small strap wrench. It seems to work well except for the loose thread engagement.

boosted79
Thanks for your response. I think I'll try a 11.5 end mill in my test VW mag case and see if that yields tighter thread engagement.