Heilcoil help

I, don't know about helicoil , but if you have suitable amount of material around the hole , you can use a GARDSERT, we put them in cast iron platens in sizes up to 1.5 inches they are pretty damn near indestructible

Are we talking bottom end main bearing caps, connecting rod caps, or head bolts?

If it's critical (a main cap is) and going into cast iron, I wouldn't go helicoil, get the solid time-sert style repairs

- they have a lot more 'meat' to them, and they have a top flange to keep them from going too deep, and the threads lock in at the bottom so they wont back out.

They also have the Big-sert style with a thicker sleeve, if it has been fixed once already and the heli-coil failed.

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On the bolt? That's what your sentence seems to say, though I suspect that you mean in the casting.

I can give you a definite "Maybe!". :-)

It depends on what is around that hole. Remember that the Helicoil requires you to drill the hole larger and then tap it with a (usually) special tap, since the tap has to be the same TPI as the original bolt, but much larger in diameter.

So -- you need to see whether there is sufficient meat around the hole to allow this. Will the threads cut into the cooling water cavities? Or into the combustion chamber? If not, it should work, and be stronger than the original thread was.

Note that you can also get self-locking Helicoils, About one in three turns has a kink in it to serve to bind the thread a bit, but you should still be able to unscrew the stud. This might be more convenient, if you don't have to replace the studs each time the heads come off.

O.K. But fun also needs to consider whether it will fail at some point when you are out on the water and a serious squall is coming.

Good Luck, DoN.

Helicoils are a standard repair for missiles, certainly ought to work for you.

Dan

Neal I would suggest a Keensert insert. They are solid metal thread repair inserts with locking tabs to prevent movement. They also use standard taps to install as oppose to helicoils which require special taps. They are available in thinwall and thickwall. The main question is how much wall thickness is available around the hole. Check the chart on the url here,

In repairing aircraft turbine engines the repair process was in order of damage.

1- helicoil 2-twinsert(a helicoil in a helicoil) 3-keensert 4-HD keensert. You can also get solid keenserts that allow you to move misplaced holes.

Neal wrote:

I have put a

devastated by having

in to

spin. All of

this

into this block

60ft/lbs when the

installing this

Neal, try a Keensert, they use the next size up tapped hole and lock the insert in with 2 pins. We use them all the time in heat-treat fixtures that take a lot of abuse and have found them the only way to go. JD

Interesting. I've never seen, nor heard about, the double helicoil repair. Is that so the inner one can be changed in case of wear, or does it make a stronger repair somehow?

Heh. Sort of like those 'bolts with a bend in them' you see on the special bolts chart! :)

Jim

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I've built a lot of small-block chevy race engines and can't figure this one out. Do you mean the *main* bolts for the crank? The connecting rod bolts? Or the head bolts. If it's the cap bolts for the crank (or the rod) you are putting way too much torque on them. Also, did you clean them on a wire wheel? Also, tapped out the female end?

Also, a fix that "works" is go buy some Belzona liquid metal. They make stuff for the Navy subs and commercial. One kind will machine nicely and I have fixed cracked *heads* with it......Look for a distributor in your area. Another option is to tap to the next larger size, if there's room in the walls....HTH..

I Don't understand the confusion. I AM REPLACING THE CRANK SHAFT MAIN BEARING CAP BOLTS. I ordered NEW bolts, ran a NEW tap down the threaded holes and blew out the holes with compressed air. THE THREADS PULLED OUT OF THE CAST IRON BLOCK. I have rebuilt many engines (mostly diesel)and as long as I can remember have heard the main bearing cap bolts referred to as MAIN BOLTS, sorry if I confused any of you who don't understand my frame of reference. I have no idea why anyone would think I would want to helicoil a BOLT!!! NO I DID NOT OVERTORQUE, the torque for this engine is 75 ft/lbs and I never achieved 60. Because the bolt hole is close to the bearing and the fact that only about half of the original hole was tapped in the first place, I am going to use a long helicoil to double the amount of the original threads. The new bolts have enough threads to allow for this. I sincerely thank those of you with HELPFULL input.

Well, I understand your frustration, and hope you have indeed recieved some help. So "only half of the original hole was tapped./"

The new bolts have enough threads to allow for

Sorry, I will stay out of the discusson.

LOL. Questions about helicoils always seem to attract the fuckwits out of the woodwork. Your original question was quite clearly stated and obviously referred to the main bearing cap bolt threads in the block. A 1.5xD helicoil will take as much torque as you can put on the bolt that goes into it but longer ones are available and 2x would probably not be a bad idea. I'd be wary of altering the start position of the original thread by too much though because the unengaged length of the bolt affects the stretch and hence its ability to stay done up tight at a given torque.

I've never actually come across a stripped main cap bolt thread in 20 years of buillding race engines and I'm wondering if the new tap you ran down the holes had a burr on it or was faulty in some way and damaged the threads. If so it might be worth looking at the other threads you tapped out. Did any unusual amount of swarf come out?

I've also never found the need to tap out main cap bolt threads because nothing can ever get into them and theoretically they can't wear or corrode cos of all that oil slapping about all over the place. If a bolt runs into them cleanly and you give them a wash and blow out they should be fine without a tap.

As Dave says, stripping a main bearing bolt is very unusual. I would suggest a helicoil repair over the thick walled types as you are so close to the edge of the casting and a helicoil is the thinnest repair available. To insert a helicoil, the hole is drilled out to nominal size. A damaged 1/2"UNC is drilled out 1/2" and then tapped and helicoiled back to original. There are tabulated tapping drill sizes available but they are very close to this rule of thumb. I have tapped for helicoils without drilling when the old thread is cleanly stripped especially in soft metal. The helicoil tap is not a standard size as others have said. In addition to the points that Dave suggests, I would crack test the block. A hair line crack may allow that area to flex slightly opening the bolt hole when it's torqued. It may also be worth checking the new bolts. It isn't unknown for threads to be made undersize. His point about the stretch of bolts is a good one to consider when positioning the helicoil. I hadn't considered that before, thanks Dave

John

:)

Dave have you ever heard of doubling up helicoils, as another poster has indicated?

Thanks - Jim

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Based on a few searches - NOT the Helicoil site, you need to register and download all sorts of stuff - the twinsert is a special outer coil that you put in, then you put in the helicoil as an inner and final thread repair. No mention of why that's better.

||Jim || If you want to jump though all the hoops on the Helicoil site and ||register to get the downloads for the catalogs (a real pain) ||

||and look for Oversize and Twinserts catalog. || The Keenserts from Carr Lane are at |||| || I have used the solid ones to relocate a hole 1/8-1/4 away. I used ||an end mill to locate the new hole near the eage of the old hole and ||then drill and tap for the keensert.

All of the solid inserts require more metal removal than Helicoil and their clones. In my experience, Helicoil is the only way to go for a headbolt thread failure. Another possiblity is there are threads below the stripped ones, is a stud kit.

Texas Parts Guy

Not until I used Google no. I've never personally come across a thread restoration job where a standard helicoil wasn't the obvious and easiest answer so that's all I've ever used. Let's face it, if the original thread was properly designed and up to the job then a helicoil repair will be stronger still. I've also never known a properly inserted helicoil fail. Only if the parent hole has been chewed up to a larger diameter than the drilling size for the helicoil will some sort of larger insert be required.

Others mentioned using a stud kit. This is a good idea. Another thing to consider is using the kits out there to turn a standard 2-bolt bottom end into a 4-bolt. If it is a 4-bolt already, you do not have the luxury.