Hitchcocks Forum

Hi guys. Amongst the electrical failures of last month on my 1996 Indian 535cc (dual coil and regulator) I’d almost forgotten the unexpectedly loose head nut (nearside, by the plughole) – which I thought had loosened after running in post-rebuild.br>
But NO. The stud threads are OK and it turns in OK up to ~15ft-lb then turns without going deeper (I only ever use ~20ft-lb using a tested torque wrench). On retrieving the stud, lots of curled pieces of aluminium meaning the stud has pulled out of the crankcase - gives that sick feeling!!<

So it must be Helicoiled or Timesert or Recoil or “an other type” of re-threaded studhole. I’ve read up on the several discussions on this board over the past 10 years and see it is possible with helicoil examples, but our hosts sell “Recoil” types which may differ from the helicoil examples discussed, hence my 3 questions below:

1. Can a Recoil thread repair be done with the engine in situ or must I remove the whole b***y lot (which I’ve just put together after work on the crankshaft)?

2. Can anyone suggest which is the better type of repair type to use? (note I am not interested in fitting a threaded insert unless I have to remove the crank etc).

3. Since the other 4 such threaded holes are all the same age, and all in the same crappy indian aluminium, do you think I should thread repair them too even though they don’t appear to need it now?

Any thoughts or advice?

Thanks, ChrisD

Recoil - Helicoil; 6 of one, Half a dozen of t'other.


5/16 BSF, do all five threads.

Hi, yes it is possible to do the repair with crankcase in situ.You must be accurate with getting the drill and thread tap dead vertical. Vince

Imagine stripping it all down, repairing one thread, putting it all back together again only to find a second one has failed as you torque it up.... So do all of them! . This reminds me, I need to do a similar job on my tuned Reliant 850 engine that was in my Liege trials car. I treated it to a ££££ professional rebuild, only for a stud to pull out of the block after 3,000 miles and the head gasket to go. The final straw for that engine - the car now has a supercharged 1.0 Suzuki engine.

The two risks of doing it in-situ are the potential for wandering off centre with your drill/tap and the possibility of getting swarf in the engine. You can mitigate both these risks by a slow, careful approach. I generally heavily grease the drill and tap as well as thoroughly packing any open engine orifices if doing this kind of work in-situ and frequently wipe and re-grease them to remove swarf.



If you were particularly paranoid about wandering off-centre, it would be comparatively simple to manufacture a drill guide on a pillar drill using the head gasket as a template and slide it down over the adjacent studs. However, there is an existing hole to centre the drill so as long as you don't go mad, it should be fine (if you ever rolled a standard bullet engine studs on a sheet of glass, you'd see there is a fairly high tolerance we're working within). The alloy is pretty soft so you can even use a hand drill if you want to take it really slowly.



I'd be tempted to do all of them.

I should add that if I was particularly worried, I'd take the whole thing to my local light engineers who has a small drill press and boring bar be can fix to the top of the engine.

The alternative would be for our hosts (or somebody) to come up with a couple of suitable jigs to ensure that the drills and taps are applied perpendicular to the crankcase mouth, supplied with a bit of Hitchcocks' Performance branded rag to keep any out of the crankcase!



A.

Sorry, insert the word "swarf" into he last line of the above. Aagh!!!



A.

Drilling jigs would be compaaratively easy to make. They could just slice up any sub-standard barrels they get sent.

A drill guide can be made from an old alloy barrel. The stud holes may need to be enlarged first, but a drill bit will self centre as it goes down the holes. then, you just need a long drill bit of the required size and drill with the barrel placed as it would normally be and you can drill nice, straight holes in the right positions. It works, I have done it and it also helps control any swarf, although it doesn't hurt to stuff some rags into the crankcase mouth.