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PhilW

Threads stripping

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Hi

Due to an oil leak between the cylinder head and the exhaust cam housing i have removed the housing after checking all tappet clearances first.  All were fine and around mid spec.

  • Took off housing, cleaned up surfaces and refitted using correct gasket sealant from PNM.  The housing is held on with two nuts on studs that are fitted into the head and eight bolts.  On fitment one of the studs span and stripped the thread in the head.
  • Removed housing and helicoiled the stud with no problem.  Unfortunately 4 tappet shims fell out and got mixed up.  Refitted housing with tappets as I thought they should be..as they fell.  Incorrect!  2 gaps were very wrong.
  • Removed housing again. Measured the two shims and made a note ready to buy new ones.  Then swapped the two incorrect shims as one gap was very wide and one very small, and refitted housing.  Second stud into the head stripped its thread.  
  • Removed housing again and helicoiled the second stud.  Refitted housing and the first of the bolts has now stripped its thread. aahhh! On a brighter note shims seem to be OK and all are measuring OK, assuming the one stripped thread does not affect the measurement.
  • Now have to remove again!!!

I am using a torque wrench set correctly and calibrated.  In fact the torque on these bolts is minimal.

What do people suggest.  Drill the lot and helicoil them all?

Thanks for any advice or resolutions from similar experiences.

 

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Upgrade today to remove Google ads and support TLF.

Yup, helicoil the lot if you can.  Been there too many times!  Very often it's due to debris in the drillings.


British Ambassador to Florida, New York, Denmark and Newfoundland.  And Sweden.

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I use a whiff of threadlock and just tghten these by feel - which isn't much more than take up the slack and then nip up a tiny bit more.  (as its a metal to metal joint, more torque is just pulling harder on the threads)   Its curious that the studs have also stripped, I would have guessed these would have accepted more torque than the screws.  What is the 'book' setting?

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Sorry to hear that Phil. Sounds a ball ache. Yep Id say maybe with age and heat the threads have become weak.

Hope you are all sorted soon.

buddsy


 

"Belief is the enemy of knowing" - Crrow777

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Simon's just had the same issue with ours. The air was blue, well nearly. All helicoiled now.

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Been there, re-threaded that, do 'em all whilst yer in there. Softest aluminium I ever worked with, compounded with the need to on/off/on off to get valves set.

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Well, Thank you all for your experiences.  I have spent all day working carefully and cleanly and helicoiled them all.  Once all done I tested all of them with the bolts.  3 when i remove them seem to chew the end of the bolt. No idea why.

Anyway once reassembled every gap was wrong and very wrong.  Problem now is when it is taken off the bolts will probably be chewed by the helicoil.

Does it make a difference which way round the shims are put in as the shims do seem to have a small indent.  If it does i wonder if they are all upside down. 

I absolutely FXXXXXX give up!!!!!!

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Yes, it does, Phil. The indentation is wear from the valve stem, and you can measure them up with a micrometer if you can get it to fit inside the dent. Or you could turn them over!


Margate Exotics.

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Thanks Ian.  To be honest I have just lost interest.  getting towards the end of the summer and have not had a car on the road at all.  Every step is a problem, although this may well be my stupid mistake.  I think I am just going to have a break from it and look again when Im in a better frame of mind.

Looking forward to next summer now I think.

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Thanks Mike.  Both cars are trying my patience this year.  I just cant work on them every spare minute as I have so many other things. What with work, a house that needs attention,   and just life in general its just too much.  I am just going to retreat from the battlefront and come back with more fire power next time!!

They will not win long term

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Just had exactly the same problem! 2 studs stripped the threads at the exhaust pulley end so helicoiled them and when reassembling another stud at the opposite end did the same. Can't be bothered to take it all apart again so fingers crossed it'll see me through the rest of the summer at least and I'll worry about it when it starts leaking. At least I know what to do now and have all the helicoil gear to hand as and when! 

I've always been proud of the fact my car spend more time on the road than off but this year I've  probably been on the road 1 month out of 7 though there have been some largish jobs being undertaken.

Hang in there!

Pete


Pete '79 S2

LEW Miss September 2009

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Cheers Pete.  I need a break from it.  Cleared up the garage yesterday and left it with the engine sitting nicely for ease of access on a trolley.  Floor swept and all tidy so a nice place for when I return to the challenge.  For sure though it will be a few weeks.

Maybe we can console each other at Hethel on 29th if your coming?

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I've had many threaded holes on my engine strip out (cam housing, water pump, engine mounts). I've found something better than helicoils, called Time-Serts. Helicoils are a piece of wire, where as Time-Serts are basically an oversized bolt, threaded inside and outside. I HIGHLY recommend them. They are available in the US, but I think people in the uK have had trouble getting them. I found them on Amazon. If you are in one of the non-US countries, you might try going to Amazon.com instead of Amazon.co.uk, or whatever.

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Interesting.  I absolutely detest them.  I find them weaker than a standard helicoil, and if they give up (more often than helicoils in my experience), the remaining hole is huge and difficult to repair.


British Ambassador to Florida, New York, Denmark and Newfoundland.  And Sweden.

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It's a bummer with these old cars. I remember working on the 1980's BMW engines, the tappet adjusters were a off-centred cam, and the threads on the tightening bolts used to strip on a regular basis. Never got round to finding out why, but looks likely from heat cycling and metallurgy composition of the metal.

482871837_Screenshot2019-03-15at10_19_06AM.png.407786e051cf98b61e8c449476c567c4.png

 

 

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