Helicoil

[Andy8421]

I have managed to remove the exhaust studs from the head of the Sprint I am restoring. Not too much drama, but in two of the stud holes the threads have corroded such the the top couple of threads are pretty much gone.

I can still screw a stud fully into the remaining thread (which seems fine), but I am thinking it would make sense to install Helicoil or similar inserts while I can get to the head, rather than wait until I have a problem and the head is in the car. Do those of you who have done this think this is a good idea?

I have never tried Helicoil, but my son tells me aerospace companies use Helicoil as matter of course in threads in aluminium, so this sounds like a robust solution. Again for those who have used Helicoil, should I use Loctite or similar to lock the insert in place? Opinion on the web seems split 50:50. There is a gentleman who seems to know his onions on the web who recommends Loctite 2620 for studs for 'headers' (whatever they may be) as the Loctite is high strength / high temperature.

Finally, I expect I may well face other thread problems, particularly in the body bobbins. Has anyone experience of using non-Helicoil 'lookee likeee' products? Chronos (reasonably well thought of engineering / model engineering supplier) have their own brand kit which covers most of the sizes in the Elan. It is helpful having the kit, or should I stick with Helicoil?

https://www.amazon.co.uk/Chronos-HELICOIL-MASTER-THREAD-REPAIR/dp/B08MQHW8YV/ref=sr_1_4?adgrpid=102525008062&gclid=EAIaIQobChMIwaXwkJCb-QIVCu_tCh3HrgnFEAAYAiAAEgJr8_D_BwE&hvadid=606133513387&hvdev=c&hvlocphy=9045777&hvnetw=g&hvqmt=e&hvrand=14527314186537796524&hvtargid=kwd-931414727945&hydadcr=8460_2283976&keywords=5%2F16+unc+helicoil+kit&qid=1658995719&sr=8-4

As always, any advice most welcome.

Andy.

[smo17003]

Recoil is another thread repair insert brand that we used successfully at work.

https://youtu.be/NcuCairFi2E

https://docs.rs-online.com/a06c/0900766b80033b89.pdf

[rgh0]

If using studs no real need for thread locker with the helicoil, just bottom out and tighten the stud. The threads in the head also run cool due to the head cooling so no need for high temp loctiite if you do use it.

cheers
Rohan

[Andy8421]

Thanks for the feedback. Helpful as always.

I took a picture of the stud hole, and have answered my own question about whether I should have a go with Helicoil. The thread is worse than I thought.

Exhaust stud hole

There is a guy on Youtube that my son follows - Abom79 who has done a helpful 'how to' for Helicoil. It doesn't look that difficult.

https://www.youtube.com/watch?v=zAXVvhpnuUU

[pharriso]

There is a gentleman who seems to know his onions on the web who recommends Loctite 2620 for studs for 'headers' (whatever they may be) as the Loctite is high strength / high temperature.
Andy.

Headers are Exhaust Manifolds in American, so relevant

[Andy8421]

There is a gentleman who seems to know his onions on the web who recommends Loctite 2620 for studs for 'headers' (whatever they may be) as the Loctite is high strength / high temperature.
Andy.

Headers are Exhaust Manifolds in American, so relevant

I am afraid the 'Headers' comment was my poor attempt at dry humour. I lived in the US for a number of years, and just about know my fender from my rocker panel (whatever they might be!) .....

[Elanman99]

I would only recommend Helicoil if you have the equipment or skills to ensure they are fitted perpendicular to the surface. I would not attempt to freehand drill and tap the head casting whilst it was still in the car. The studs need to be parallel to each other, if the manifold is to slip on the studs and line up accurately.

Several jobs (like engine and/or engine mount removal or manifold removal) on the Elan are made much easier if the exhaust manifold studs are removed using two nuts locked against each other.

There is probably enough material in the head casting to be able to tap the existing (5/16 UNC) a couple of threads deeper which would make up for the lost/damaged thread in your picture although, in practical terms, its probable that you already have enough good thread for the studs.

Ian

[mbell]

Again for those who have used Helicoil, should I use Loctite or similar to lock the insert in place?

You should follow the instructions for the insert type you are using. For heli coil that is no thread lock, they are designed to be self locking. When you fit them you winding them in compressing the outer diameter. After that the will un coil a little, expand and lock in place.

[RichardHawkins]

Andy,

I have used both Helicoil and Recoil, can’t really tell any difference in use. As others have said you do need to drill the holes square to the head. I first came across thread inserts in the 1960’s whilst working for GEC on some kit for the Admiralty, all the aluminium threaded holes had inserts.

Hope this helps,

Richard Hawkins

[Andy8421]

Thanks all.

I have the equipment, but not necessarily the skill. My undergrad degree is Electronic eng, but the first year of the degree was common across all engineering subjects, so I do have some basic workshop training - albeit many years ago.

Over the last 10 years or so, I have been collecting machine tools, and have a Harrison 140 lathe and a Bridgeport turret mill - both in pretty good shape. As long as I figure out what I am doing and take it slowly, I should be OK.

I will practice a few times on some scrap aluminium first.

[GLB]

I helicoiled the bobbins in the body to chassis location. Was easy and worked well. Plenty of meat in the bobbins. Gary

[2cams70]

Thanks all.

I have the equipment, but not necessarily the skill. My undergrad degree is Electronic eng, but the first year of the degree was common across all engineering subjects, so I do have some basic workshop training - albeit many years ago.

Over the last 10 years or so, I have been collecting machine tools, and have a Harrison 140 lathe and a Bridgeport turret mill - both in pretty good shape. As long as I figure out what I am doing and take it slowly, I should be OK.

I will practice a few times on some scrap aluminium first.

Don’t consider that an impediment! Although I’m a mechanical engineer the best teacher is practical experience. A lot of professional engineers especially in the corporate world are far more skilled in politics and would not be able to pick up a hand drill and use it even if their life depended on it!

[john.p.clegg]

Andy
Go for it , it's not rocket science and the helicoils will make a much better job than threads in aluminium , so much so that you will be able to fit and remove the studs ad infinitum , bearing that in mind you may wish to consider upgrading to socket cap screws which will make re-fitting the manifold in situ a much easier job...

John

[alan.barker]

Never use loctite on thread insert.
If you want it to lock and not unscrew use "helicoil locking insert" coloured red.
I just use standard "free running" inserts NOT coloured/dyed.
Alan

[fattogatto]

TIMESERT is a step up from basic Helicoil. More difficult to remove, though.

https://www.timesert.com/