Lotus Elan

Helicoil. advice on an issue please

PostPost by: alan.barker » Tue Jun 16, 2020 2:20 pm

If a little Copperslip grease is used on Plug thread it can help with heat transfer
Alan
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PostPost by: wotsisname » Tue Jun 16, 2020 3:53 pm

nmauduit - I think you have identified the why. It was more difficult to start this one, compared with the first and I definitley used a bit more pressure on the tool.. the first went in very smoothly, so a learning there.


Elanman99 - The bolts that came out were 3/8" UNC.. the parts list (for the +2) isn't very helpful, so I assumed this was correct.
The head looks like this bit has been worked on before. The recess for the thermostat to sit on is deeper on the camshaft side (1.6mm vs 0.5mm) and the face is flat. I suspect it has been refaced but was not set up level.
I had the head rebuilt some years ago , possible it was done then, or more likely prior to my purchase. It was run on a dyno, but the car has been off the road for some time since.

"unless the holes are blind the gasket around the fixing holes will be very narrow" I'm not sure what you mean by blind in this context.
The gap for the gasket (between bolt hole and recess for the thermostat) is 3mm & 4mm.
Would it make sense to use a thicker gasket in this application ? I was considering RTV silicon or blue hylomar.. what is the current concensus ?


2cams70. Thanks for the info about the tool.. I will look for that in the UK... I really don't want to make this problem any worse, so might be a good investment.
I made a jig from 1" square aluminium bar using a drill guide to give me two vertical holes (3/8" & 9.9mm for the helicoil kit) with the correct separation. I did the worst thread first, bolting the jig to the "other" side using an exhaust type stud with brass nut and also clamped it with a G clamp. I used the same to guide the tap in, for the top 1/2 or so of the thread. [in case this helps anyone else - but in an ideal world I would probably take the head to a machine shop ]


Thanks for ALL the input.. The extra information about helicoils /inserts is all really useful. I will try the blob of grease.. have been using a small vacuum cleaner.. but that approach seems likely to cost me a lot of my brownie points..

Adrian

[hopefully this posts OK.. third time I have tried to reply to the topic]
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PostPost by: wotsisname » Tue Jun 16, 2020 4:25 pm

I decided to buy the tool. I had a little (gentle) attempt - filled the hole with a bit of oil and gently tried to rotate the coil. It rotated out about 1/4 turn and then seemed reluctant... I think it's worth hanging on a couple of days

Amazon/ebay not too useful for the extract tool, either out of stock or from China.. so could be a while.
If it helps anyone in the UK

Recoil RC50003 3/16"-5/8" (M4-M24) ~£16 inc VAT & P&P
https://www.recoilshop.net/index.php
has a range of the inserts that have been mentioned, etc

Adrian
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PostPost by: Elanman99 » Tue Jun 16, 2020 6:32 pm

By 'blind' I meant a hole that is closed at the bottom and not one that breaks through into the water jacket.

I have a spare head but its not to hand at the moment so I cannot easily check, but from memory I think both these stud holes are blind. As it happens the water valve tapping on the head on my car has been fitted with a helicoil which is a really poor solution because, firstly its supposed to be tapered thread (and helicoils are not) and secondly a being a wire thread insert its has a built in leak path!

It was the leak possibility that prompted me to to comment on the reduced annular width of gasket with larger diameter threads but since there is no coolant in contact with the stud its not going to be a problem.

I had not seen the extraction until it was linked to here, but I am far from convinced that it work very successfully on your failed insert. To remove the insert mechanically requires it to be unscrewed, imparting the rotation force with that tool relies on its two sharp edges digging in to the insert metal, to do that it also tries to expand the insert diameter making it locally larger diameter, that seems counter intuitive.

I think I would slightly modify what I said originally. Using pliers or mole grips pull up enough of the exposed turns, and put a loose fitting bit of steel rod into the insert and clamp the exposed tail of the insert to the rod. If you then rotate the rod, clamp and insert in an anti clockwise direction the insert should just wind out.

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PostPost by: wotsisname » Tue Jun 16, 2020 9:08 pm

Ian,
Yes both holes are blind, and I took a lot of care to go no deeper. I am thinking the insertion tool (forked rod) might be useful in the way you describe. I've got a few other jobs to do so will wait and see if the tool does the job first... I'm a bit nervous about the whole thing...
Adrian
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2000 Elise S1 - Sold
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PostPost by: alan.barker » Wed Jun 17, 2020 4:48 am

A few tips:
1.When the Heilicoil has been fitted try a Set Screw inside right down to the bottom using your fingers only. To check that the bottom of Helicoil has not jumped.
2. Use only Set Screws to attach Thermostat Housing (stud or bolts will jam in the Helicoil with their plain section).
3. Flatten surface of Thermostat Housing emery cloth on flat surface. Use thin Gasket with sealant to assemble( a thick gasket if over tightened will bow housing).
Alan
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PostPost by: 2cams70 » Thu Jun 18, 2020 10:28 am

Elanman99 wrote:I had not seen the extraction until it was linked to here, but I am far from convinced that it work very successfully on your failed insert. To remove the insert mechanically requires it to be unscrewed, imparting the rotation force with that tool relies on its two sharp edges digging in to the insert metal, to do that it also tries to expand the insert diameter making it locally larger diameter, that seems counter intuitive.


Having bought and used one in the past I can assure everyone that it's a piece of cake removing an insert with this tool and there is no risk of damage to the threads that have already been cut to fit the insert. The tool like a chisel cuts a small groove in the top face of the insert thereby creating a key so the tool can lock in and so the insert can be then unscrewed. The action of winding the insert in an anticlockwise direction also reduces it's diameter like a coil spring that is held stationary at one end whilst being rotated at the other. This relieves the friction between the insert and the hole it is screwed into so that it comes out really easily.
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PostPost by: wotsisname » Thu Jun 18, 2020 10:01 pm

20200618_211230~2.jpg and
nuff said


Tool arrived and worked a treat. you position it at 90degrees to the end and tap with a hammer to create the grip. The coil tightens as it shrinks, then rotates and relaxes and repeat until it winds out.
Ran the tap in and out a few times then (carefully) put the new helicoil in. The top of the thread was hard to find with the tap and the coil.. am assuming because no chamfer present.
Didnt have much time tonight. Will put it all back together and test tomorrow evening. Hoping to move the car under its own power at the weekend, the first time in a long time.

Cheers for the input
Adrian
1968 Elan plus 2 - project
2007 Elise S2 [modified with a Hethel 70th sticker (yellow)]
2000 Elise S1 - Sold
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