Sparkplug thread repair. 1.3 engine.

[chrishawley]

4-cyl engine. Excellent low milege condition. Ready to fit. 'Cept: Previous operative had brutally cross threaded spark plug #3. Once extracted, a new plug could not be inserted. On the off chance I tried an M14 x 1.25 tap to see if the threads would 'pick up'. Nope. Rather, the damaged thread just stipped off the wall.

So, what are the options in terms of repair and thread inserts? The head's on the engine and it would be nice not to have to remove it, but removal is perfectly possible if need be. All points of view would be appreciated. I'm reasonably conversant with helicoils (etc) but never had to do a spark plug before.

Don't mind forking out on good kit as much a needed.

Thanks in advance.

 

[Clive]

I borrowed a helicoil kit to do a plug on an MX5. Head on. 

I used an airline to blow debris out, and then an underseal gun with abit of pipe on the pickup tube to act as a vacuum. All was well....

[Stratton Jimmer]

I have had helicoils fitted to bike engines in the past without any problems. I have to admit that I never did the job myself though. I was ever cautious afterwards in installing spark plugs and always used a torque wrench to ensure there would be no further damage. 

[Pete Lewis]

there are a good few repair kits on ebay to retap and fit a collar as  sets or individuals

Spark Plug Tap Thread Repair Rethreading Set Kit M14 x 1.25 16pc 5056133360080 | eBay

Pete

[Piglet]

A torque wrench on plugs? I was taught to get them finger tight then just nip them up.

Alex

[Wagger]

There is nothing wrong with using a torque wrench for any thread, but low reading ones I have not seen. A loose plug can damage a thread more that a slightly overtightened one. Vacumm, pressure, rattle and burning gases blowing through. Wish I could find the Gorilla who tightened my plastic oil filter on my BMW. It is a 35mm a/f nut with 2.5 lb on it. He'd used 25 lbs!

[Pete Lewis]

15 hours ago, Wagger said:

He'd used 25 lbs!

had that on a X Trail   had to remove the whole housing and the alloy filter cover shattered before removal and the filter was worse than clogged

never been off for years .

it was dealer serviced  .....!!!!

and agree on spark plugs finger nip + 1/4 turn to seal the washer 

Pete

[Stratton Jimmer]

On 10/06/2022 at 11:58, Pete Lewis said:

spark plugs finger nip + 1/4 turn to seal the washer 

Yes, that was what I was taught by my father and would still apply it if no torque wrench was available.

[Pete Lewis]

many torque figures were devised to aid tightness control with  unskilled labour to give a consistent result 

some joints need careful control but so many just needs a good hand and the length of spanner does the rest 

there is far more damage and problems by gorilla hands than anything being Loose 

Pete

[ahebron]

Torque to yield on modern vehicles scare the bejesus out of me. 

[Iain T]

14 minutes ago, ahebron said:

Torque to yield on modern vehicles scare the bejesus out of me. 

I had four tyres fitted and I told the fitter to tighten the wheel nuts to 50ft/lbs. He said glad you told me I normally tighten to 100-110ft/lbs! 

[ahebron]

Modern wheel nuts can take a lot more torque than the spindly Triumph ones.
 

[johny]

And the fitters want to whack them up as tight as possible to avoid absolutely any chance of them coming undone...

[68vitesse]

Understood alloy wheels need a a higher torque than steel disc ones.

Regards

Paul.

 

[PeteH]

I once witnessed a very expensive set of wheels which where scrap. Cause? Over tightening. Close to 2 Grand in the skip .

[Pete Lewis]

the wheel studs are if standard are 3/8 x24 unf   they are tempered and will take the 42lbft specification  , bear in min that is higher than the normal torque of 31lbft

if you exceed the 42 no matter what wheels or nut design  you have you will be pushing the studs to their yield and subsequent fracture 

 the 7/16 stud of the bigger range are specd at 65lbft  its simple to fit the big saloon studs or go to M12 metric  then you can use 65lbft safely 

these specifications are there for a good reason ,  dont let the muppets wreck your studs 

loosing  a wheel is an expensive body repair jobby .

Pete

 

[Peter Truman]

Also remember if you have a Sprint the wheel nuts early models only 3/8in and are Alloy and need to be torqued up very carefully, I'm fortunate my tyre Retailer (Michelin) only ever hand tightens them up NEVER uses a ratchet gun!

Don't get me onto Jag X type and XF wheel nuts where the one piece nut and washer shear at the nut washer interface requiring expensive surgery to remove the threaded portion of the washer!!