While replacing the water pump on my 4.9, I managed to strip one of the bolt holes for the 10mm bolts (couldn't get the torque wrench in that spot). Does anyone here have experience with Helicoil or Time-Sert, and what are the pros and cons of each? Also, does anyone know what these thread repair kits run, price-wise? Just trying to make up my mind between the two, and leaning toward the Time-Sert.

Um, Time-Sert is considered far superior by many - my machine tech (machine shop) instructor swore by them. They're a solid, thin wall bushing that threads into place and has threads on the inside. The last few threads aren't formed, so when you run a form tap through it, when it forms the last few threads, it mashes the timesert into the outer threads, locking it in place. It all comes at a cost, of course. I think for a 10mm bolt, it's gonna be like 50 bucks, ballpark?

Helicoils, you know how they work, I assume. I bought a 10mmx1.5 Perma-Coil kit for 25 bucks. After debating on what I should use for the cam timing belt idler pulley bolt that stripped on my 3.4 TDC (note: critical), I finally decided to give Perma-Coil a shot. Despite the fact that I was repairing stripped threads in aluminum (Im assuming you will too) that had to hold 37 ft lbs, it worked like a charm.

Do the threads have to seal against water? It might change things some, but not by much I imagine. A little silicone ought to help.

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Chris

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I routinely helicoiled the threaded head-stud holes in the aluminum case halves of my Corvair race engines. Without the helicoils, the studs would pull out; with them, they never did. I never used Time-Serts, so I can't provide you with an A-B comparison.

Time-serts kick @$$ for Northstar head bolts.

The actual insert is very cheap <$5, but the tool kits to properly install can be expensive. I've never worked with one other than the N* head bolts. Try giving time-sert a call and talk to them about it.

For your application, a helicoil would probably be ok. They're not for the N* head bolts, but those are under a lot more tension.

Thanks for your help, all. Pluses to all who responded. I may wind up having to tip the cradle to do this repair; if that is the case, I will use time-serts on each hole (I used to have a Corvair, too) for the water pump. They'll be a bit more expensive than the helicoils, but the end result looks more stable.

[This message has been edited by Vonov (edited 02-10-2005).]

Just thought I would add this thought....
I have used Helicoils for many repairs and would suggest, if your setup will allow it, to use a stud rather than just bolt it back up. Using a stud will eliminate wear when many teardowns (racing purposes) are in order. Unfortunately, some orientations/tight places will not allow use of a stud.
Ebay is a cheep place for Helicoils!
Sandy

Thanks, Sandy, I believe I will implement that suggestion.

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Another, lesser-known option is the Keensert ( http://www.newmantools.com/kee.htm ). It fits somewhere between the Helicoil and Time-Sert. It is a solid piece, like the Time-Sert, so it is more durable than the Helicoil, but does not require the special installation tool, like the Time-Sert (they sell one, but the locking tabs can be pressed in with careful use of a hammer). The Helicoil generally requires the new hole to be drilled/tapped one sizer larger, whereas the Keensert, with its thicker body, requires the hole to be larger (they make several different thickness inserts). This could affect you if there isn't much material around the hole to be repaired. They are also removable, if needed. I have used the Keenserts several times, and they are easy to work with, and very robust.

Marty

Use the helicoil. Any solid thread insert is worthless. The engagement between a solid insert and the bolt will be better than the engagement between it and your hand tapped hole. Basically, it will come out with the bolt eventually. Helicoils are designed to lock in. Once they are in, there's really no way to remove them. Any CCW torsion will cause it to expand and hold the hole even better. I guess the question is: do you want it to last long enough to sell it, or forever.

Edit: wanted to add that I know this because I am a machinist, and I have tried most of the products out there for repairing fixtures our operator have ruined. For a bolt that gets tightened and loosened 300+ times a day, you will get 2 maybe 3 days out of a solid insert. The helicoils are good for months. The company I work for makes surveying equipment. We actually use helicoils in production to put steel threads in aluminum castings.

[This message has been edited by Azriel (edited 02-11-2005).]

You can actually remove a Heli-Coil (or Perma-Coil, same thing) - I messed up installing one... so I grabbed the end of the coil with a pair of pliers and ripped it straight out. Less destructive than it sounds since the wire simply unspools out of the threads without gouging them. Better yet if you grab the bottom instead of the top end.

No doubt about it, Time-Serts rock on but they're more expensive. Choose accordingly.

Edit to say: Those keenserts are new to me, cool idea. Time-serts probably lock in better though.

[This message has been edited by Blue Shift (edited 02-11-2005).]

quote Originally posted by Azriel: Use the helicoil. Any solid thread insert is worthless.

That's why Time-Sert sells two different inserts for the Northstar... one for a virgin hole that's never been repaired and another for the 2nd repair after the helicoil pulls out.

The two methods each have applications for which they are suited...

[This message has been edited by Will (edited 02-11-2005).]