Argh... Stripped out Motor Mount Bracket Bolt Hole

[930LDR]

I guess things had been going too good on the rebuild for a little too long... Tonight while reinstalling the motor mount bracket I managed to strip out the threads of one of the three bolt holes in the case (circled in Red below). Backed the bolt out and the threads were neatly coiled up on it like a spring.

I'm thinking I need to put a case saver in there but am unsure if the right size is out there and more importantly how to go about installing given that the hole is on a vertical surface rather than a horizontal one.

Any thoughts or suggestions would be much appreciated.

A somewhat related question I had relates to the threaded hole that is circled in blue. What is this for? It appears to be covered by the motor mount bracket once its installed.

[johnman001]

I believe you have a later case (post 1983) it would accept either an early mount or a late mount. The later cases have both bosses. The earlier cases didnt have both bosses.

I stripped one of those once. I used a helicoil.

[dtw]

Repair with Helicoils or even better, TimeCerts.

Then install the correct studs - this happened because you were trying to use bolts.

[930LDR]

I don't follow the last comment regarding the use of bolts. That's what was in the case when I took it apart. We're thee supposed to be studs?

[johnman001]

All the ones I have worked on use 3 bolts and 1 stud.

[Ronnie's.930]

I did the exact same thing about 4 years ago when trying to modify and mount a turbo bracket (it uses that engine bracket/bolt/boss combination that you have circled). I was sick when I did it, but I easily repaired it with a helicoil and it is a strong repair that has held up to many more removals and re-installs . . . the most difficult thing was keeping the drill, and then tap, straight and true . . . if for some reason your new hole places the bolt at an angle your can recover by drilling the engine bracket hole bigger in diameter . . .

[Flat6pac]

Using the case savers or time certs standard is the same as the timecerts used on the head studs for the mag cases. I believe it 10x1.5.
Bruce

[Walt Fricke]

Helicoils are often found in stud or bolt holes where the engine and tranny bolt together. Work fine, better than threaded aluminum if you use a bolt too.

[930LDR]

I ordered a timesert install kit today and will give that a whirl.

[Henry Schmidt]

Originally Posted by 930LDR

I don't follow the last comment regarding the use of bolts. That's what was in the case when I took it apart. We're thee supposed to be studs?

Hi Rob
The turbos use bolts in this application to facilitate the removal of the turbo mounting bracket with the engine in the car.

TimeSerts are the correct choice and I recommend (probably already were) you do all three holes where bolts are installed.

[930LDR]

Thanks Henry I did order enough of the serts to do the other three as well. Little nervous about getting the drill lined up straight so as not to end up with crooked threads...

[Henry Schmidt]

You may be able to use the cradle as a pilot tool.
If the drill fits freely you're in.
The tough part is aligning the tap. Be patient and you'll do fine.

[herman maire]

Mine are also stripped. I was wondering what to do.... perfect timing for this tread.

[VitoV]

Originally Posted by 930LDR

Thanks Henry I did order enough of the serts to do the other three as well. Little nervous about getting the drill lined up straight so as not to end up with crooked threads...

Drill a hole the same size as the TimeCert drill bit in a piece of scrap. Aluminum, plastic, wood, whatever. Then place that piece over the stud hole in your case as a guide for your drill.

If you use a nice, thick piece of whatever, say 3/8" or more, you won't have any problems getting the drill in there straight. You could also mark the drill bit with a sharpie so that you know how deep to drill. If your guide block is X thickness, and the stud hole is Y deep, then make a mark on your drill bit at X+Y inches (mm) and drill until that mark is level with your guide block. Takes out all the guesswork and makes it a quick and painless job.

[930LDR]

All solid suggestions. Thanks guys.

[Henry Schmidt]

You could just jam an over-sized wood screw in the hole and call it good!!
My memory sucks these days but whenever I see a stripped hole in an engine case it brings back memories from my Type I days. People would use a Case Saver stud to kluge together an engine with a pulled head stud. It was basically a long head stud with a cobby, self tapping, wood screw like end that you could install in the case without removing the head.
Where's Snowman when you need him.

[JFairman]

I like Henry's idea of using the motor mount cradle as a drill guide. Wrap some masking tape around the drill bit so it doesn't catch on the hole in the cradle and start to enlarge it if you move off center.

You can wrap the masking tape around the drill bit so it works as a visual stop block if you're worried about drilling too deep.
Probably won't be able to see that with the cradle on there though.

I put time sets in there on my 930 because one of those 2 bottom 10x1.5 bolts had stripped the case threads.
When drilling out the old threads before tapping the hole for the time sert you can feel the drilling process slow down when the stripped threads are drilled out and the drill bit has reached the end of the hole.. you really want to stop there.

[Porschekid962]

McMaster-Carr

Thick inserts are great for this sort of application. With the key locks there are no worries about the piece backing itself out and a bit more insurance than green bearing retaining compound. This is standard stuff on racecar repairs in aluminum, magnesium, titanium and especially carbon.

Cheers.

[930LDR]

Just got the timesert kit. Looks like the drill bit will fit nicely inside the bore of the cradle. Great suggestion.