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 Posted: 03-22-2015 10:48 pm
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Esprit2

 

Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 289
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Barthol wrote:
(Snip)... I need to sort an issue with the belt tightening wheel . The bolt is pulling a little to the left when I tighten the belt. The thread in the engine block is not so good.It sounds like you're talking about an eccentric tensioner here. All later J-H Mk II 907s, and all Lotus 9XX engines with eccentric tensioners use a stuc to mount the eccentric. I've not worked on a J-H Mk I (rope seal) 907, but my J-H parts manual calls out a stud and nut for mounting the eccentric. Does your engine actually have a bolt, or was that a casual mis-use of the term?

In general, it's a bad idea to use bolt for a high stress, repetitive application in an aluminum part. The soft aluminum threads will take the brunt of the abuse, and wear or strip in time. A better solution is a stud, since for most applications, it's a one-time installation. Then the repetitive wear part of the assembly is taken by the studs steel threads, and little wear takes place.

If the 'bolt' can wobble about, then it sounds like the threads require a repair insert. In that case, a threaded barrel insert (like a Time-Sert) is superior to a more common Heli-Coil.

The stud needs to be perpendicular to the block's front face, and drilling the hole to accept an insert is not a good job for a hand-held drill. Taking the block to a machine shop to have the threads properly inserted will require a complete tear-down.

As an alternative (it's worth a try), apply Blue Loctite 242 to the threads in the hole and on the 'stud'. Screw the stud into place and torque it to 20-25 Lbs-ft. Wipe off any Loctite that oozes out. Lightly wipe the eccentric with oil (especially it's bore) so that any Loctite residue you miss will not stick to it. Install the eccentric and tighten it's nut to 30 Lbs-ft. Allow it to sit undisturbed for 24 hours for the Loctite to fully cure. The tension should pull the stud up square to the surface, and the Loctite should hold it in position.

Remove the eccentric, then go about fully installing the timing belt.

Regards,
Tim Engel

Last edited on 03-22-2015 10:49 pm by Esprit2