Helicoil, insert or tap out to next size ?

[v8ivor]

I have got one head bolt thread (One of the front centre bolts ) stripped in a 52 plunger barrel. I was going to helicoil it but a guy told me today that in his opinion Helicoils were useless, but the insert kits cost around £90. So, has anyone had experience with Helicoils under these torque pressures ? Or, if I tap it out to a bigger size and make a shouldered stud with a 3/8" BSF thread nut (A bit like the one inside the rocker box ) What should I make it with ?
Ivor.

[muskrat]

G'day Ivor. I'd use a helicoil. I think bsa-bill did a couple in his barrels recently.
Cheers

[v8ivor]

G'day Musky, thanks, I will wait and to hear what Bill says then. Cheers.

[trevinoz]

Over nearly 50 years I have used Helicoils in barrels with no problems.
Rather than buy a kit, is there an engineering shop which will do the job?

[v8ivor]

That's good to hear Trevor, I was thinking of just getting the tap and inserts rather than the kit and although I haven't got a 9.8mm drill bit, I was hoping a 9.5mm will do.

[Tomcat]

G'day Ivor, a helicoil is stronger than standard. There is more surface area on the outside of the helicoil which gives better purchase on cast iron or alloys. And, the bonus is you can use the standard size fastener. If anyone has problems with them it is usually poor workmanship.
Cheers Tomcat.

[bsa-bill]

Hi Ivor
yes I did use then to renew stripped/almost stripped threads on my barrels, no problems other than getting the drill perpendicular (got one a wee bit off but filed the hole in the head a tad to let it in , now thats a confession to make given the expertise here).
I've read since that a helicoill is as strong as an original thread, can't see why that would not be true once the stud is back in (oops just seen Tomcats post which states the same.)

bit surprised at your estimate of cost for a kit try here http://www.tracytools.com/helicoil-thread-repair-kits/bsf-thread-repair-kits

[chaterlea25]

Hi, All,
If I am fitting a thread repair in situ I first take a block of ally and drill two holes in it on the drill stand,
one is the tapping drill size, the other a clearance hole to suit the nearest adjacent bolt or screw hole
The alloy block is fastened to the nearest bolt hole and the tapping drill is then kept square to the bolt hole needing drilling out,
Then back to the drill stand and the block is tapped with the helecoil tap, replace the block and this will keep the tap straight
As to what to use ?? whatever will get the job done 

John

[BSA_54A10]

Helicoils are fine.
If you want a proof. Rolls Royce helicoil every bolt hole in the alloy 6.5 & 6.75 L blocks, from new.
Now the downside.
The old ones were the correct shape for each thread
The new ones are a diamond cross section and it is the same for all thread profiles so there is not as much contact area between the bolt and the insert so there is less friction and a slightly loose bolt will happily undo.
Also the reading on your tension wrench will be a bit lower due to the reduced friction.

[beezermacc]

I have come across quite a few barrels where the threads are starting to feel weak. This is mainly because the original bolts, and some of the replacement bolts available, do not use the full extent of the thread. Nowadays, if I'm building an engine where originality is not critical, I use 3/8 BSF high tensile allen bolts. I bought a stack of these a while ago and they have proved to be invaluable as they have suitably small heads, plain shanks, and can be cut to the desired length.

[v8ivor]

Thanks for all of your help ! I have ordered the Helicoil stuff (Maybe here tomorrow ) The guy that told me that Helicoils are rubbish told me that  the ridged inserts were good but cost around £90 each or set. But you have all given me confidence to go with Helicoils.
Thanks again.

[coater87]

I have never had trouble with helicoils, especially for spark plugs. The secret there is to use the ones especially made for airplanes. They are a bit pricey, but you will never worry about them again.

[Rocket Racer]

I have bought bikes with engines where people have drilled out worn threads to the next size and that can make ever taking the fasteners back to standard a real problem.
I prefer to keep bolts std, they were that size for a good reason.
So even when I find something oversized I prefer to take it back to std.

[muskrat]

I have been guilty of going oversize. In my defense I was building my A7SS racer in my humpy (bush shack) out in the bush with no electricity and kero lamps. The four rocker box bolts were stripped so they went up to 3/8". That top end is now on the '51 plunger so "one day" it'll be taken back to std.
Cheers

[v8ivor]

Well, the Helicoil 2xd inserts, tap and drill came this-morning and the thread is now repaired. After reading bills experience, I loosely fitted the head to guide the drill, then I cut a slot in the end of an old bolt to insert the coil. I was going to use a 9.5 mm drill but I'm glad that I got the correct 9.9mm drill because I think it helped centre the tap. It all looks good to me, but why the chap that I spoke to on Thursday told me that Helicoils were only any good for holding plastic will remain a mystery to me, I mean, he owns a successful motorcycle workshop (Mostly British bikes ) And built and restored an untold amount of bikes