repairing trans bolt holes

[Alan L]

Is there any special trick to re-drilling these holes? My track car has thrown a trans bolt - the hole was a bit suspect before, but has held up OK for past few years. I suspect a bad case of clutch judder/wheelspin has ripped it free.
Was going to helicoil it, or maybe tap a bigger bolt thread in (whichever gives best option).
But is there any way to drill the hole perfectly straight while lying under the car - only get one shot at this.
Thanks
Alan

[Scott Douglas]

Heli-coil is the way to go and yes it can be done lying under the car.
Just be sure to get the car as level as you can on the jack stands and/or compensate for the angle it is sitting. If you can, get a piece of aluminum and drill a hole in it to use as a drill block/guide. Even a piece of wood would work, just something to help establish perpendicularity of the drill bit.
I had to do it so it can't be all that hard to do.

[Jcslocum]

Originally Posted by Scott Douglas

If you can, get a piece of aluminum and drill a hole in it to use as a drill block/guide. Even a piece of wood would work, just something to help establish perpendicularity of the drill bit.

^^^^

What he says! Get a block of alum to put onto the hole and next bolt if you can. This will guide the bit in straightest.

[Alan L]

Excellent suggestion guys - that is precisely what I was looking for.
Thanks
Alan

[Porsche84]

I prefer Time-Certs over Helicoil. Much stronger. ++ TIME-SERT Threaded inserts for stripped threads, threaded inserts, thread repair stripped sparkplug's, Ford sparkplug blowouts, threaded inserts threaded, repair stripped threads, stripped threads, inserts threaded inserts, Ford spark plug repair,

[Alan L]

Jerry, I did a search on these threads previously - since the issue comes up regularly. What they seemed to show was that helicoil offered the widest options, in that time serts apparently require more metal removed, and no options after that?
Helicoil at least will be stronger than the old, re-tapped thread I used to have in there, and that lasted OK til I shook the hell out of the beast.
So at this point, I was planning on the least invasive of the options?
regards
Alan

[Porsche84]

That makes sense. I actually have not used Helicoils for many years. I keep a full range of Time certs on hand. Aluminum just doesn't hold up. Which part are you repairing? I haver many 915 parts if you get to a point that you can't save what you have.

Regards

[roblav]

I would have done an insert too.

[Alan L]

Hi Jerry, I just want to repair the trans bolt hole in the chassis.
regards
Alan

[Scott Douglas]

[uwanna]

Kinda off topic, but a hint to prevent cross threading the trans mount bolts when reinstalling
an engine. Loosen all four of the nuts on the mount that bolt it to the trans. That allows you to "wiggle" the mount around and finger install the big bolts to the chassis so you don't get them cross threaded. Learned this trick the hard way!!

[JP911]

Used a helicoil in the exact same spot about 3 years ago and it has held up just fine (at least 20 days at the track and 2 engine drops/reinstalls).

[Porsche84]

Nice repair!

[Walt Fricke]

I have at least one Helicoil approaching maybe 20 years service in this application.

Timecert may be stronger, but I've never seen any evidence that the Helicoil isn't up to the job. And if you succeed in buggering it up, you can pull it out and put in another one.

[Alan L]

Thats me then guys - Helicoil. If it works for Walt, it'll work for me. Hope mine turns out as nice as Scotts - then I'll be happy.
yes loosening the 4 mount bolts is the way to go, but I and the PO obviously hadn't thought of that one.
Thanks guys.
Alan

[Alan L]

Got my kit. No instructions. Do you use any loctite on the outer helicoil thread - what stops it unwinding when you take the bolt out?
And does the tang end go to the top of the thread - seems likely by direction of wind/insertion.
Thanks
Alan

[Walt Fricke]

1) No Loctite
2) Magic
3) Tang end in first (the ridge on the end of the insertion tool fits up against the ridge so it can be screwed in.If you try it the other way, you'll immediately find out which way to go).
4) When well and truely screwed (in, that is), and tool screwed back out, break off the tang with some suitable tool and fish it out. That way the bolt end can go beyond the insert if need be.

[rsscotty]

Video link

Yahoo! Video Detail for Heli Coil Installation

[Alan L]

Thanks guys.
Wish me luck - never done one before. As always, the Porsche takes you on a new journey everytime you go near it.
Alan

[pwujszuf]

I keep a full range of Time certs on hand.