leaky grub-screw

[kwaka]

G'day fellas,
On the advice of a mechanic, i had access holes (6) drilled in the head of the Z1B so as to facilitate cleaning out the oil galleries after bead blasting, bad move, any way the machinist threaded each hole and gave me grub-screws to seal them. however even after puting a generous amount of Threebond 1194 on them, they piss out oil once the engine has warmed up. Is there something else i can use to seal the threads, has anyone else done a similar thing or am i the only dope out there?
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[Pigford]

Hmmmmmmm, try a bit of PTFE tape

If thats no good, try bolts and use copper or fibre washers. A nice set of s/s allen bolts would look good

[Rich]

Allen bolts and fibre washers.

Putting PTFE on the grub screws won't really do much as there is nothing to tighten up to.

Nutlock or stud lock may seal it.

[FER]

Probably too late now but if the thread had been cut with a BSP tap the thread would have a taper and the plug would seal better . Would getting alloy plugs made be better as they would expand at the same rate as the head ?






fer

[KeithZ1R]

drill next size up tap and seal with a rubber plug before screwing in apropriate sized grub screw just a final solution if all else fails

[KeithZ1R]

sorry to much red next size up half depth

[kwaka]

The holes have been tapped with a tappered thread, as the grub screw gets harder to turn the more you screw it in. perhaps i should get the holes re-welded, can this be done with the head still on or should i remove it?

[RALPHARAMA]

If it has been tapped with a tapered thread then PTFE may well work.

Clean the thread out on the grub screw with a fine wire wheel on a dremmel. Wrap with a generous helping of PTFE. Then warm up the engine and re-tighten the screw. As you have a steel screw in and aluminium thread the aluminium will expand more than the screw, so a little tweak when the engine is at running temperature won't hurt. As has been previously mentioned an aluminium blanking screw would be a better solution, but not so easy.

I certainly wouldn't attack it with a TIG insitu - that would really be asking for trouble.

[kwaka]

The other concern i have is if the screws start to leak on a long trip, ie. will the ptfe tape eventually disintegrate. would silicone on the thread be another option?

[Steve Cooke]

I would try a low modulus silicone as I use it on the cam end caps where it works perfectly although you may have more pressure at that point, but it's a quick and easy option to try, the hardest bit would be making sure the threads are thoroughly clean.

[oldzed]

Personally I would use araldyte.
In my younger days I used to seal worn out threads in my 2 strokes plugs.
don't use the 10 minute stuff, its rubbish.
make sure there is no oil , smear with a coat of araldyte and let it cure for 24 hours.
Most of the araldyte will get squeezed out , You can wet your finger and smooth it before it cures.

[kwaka]

Who would have thought a few grub-screws could lead to such dramas, Hanging out for my first ride after a 1 year resto.

[Al]

If it were me facing this situation i would be inclined to do the following:
remove grub screws, clean threads with carbon tetra chloride (nasty business), plug the bottom of the holes with Loctite 5910, coat the threads on the grub screws or better still socket caps with washers of either fibre or annealed copper, and wind them in gently, allow 24 hours for the stuff to dry, start the engine and run for 30 seconds, drain the oil and refill and run up to full temperature again.

This is on the pressure side of the oil pump so no problems with it being 'sucked in'

Loctite 5910 is akin to the 'gorilla snot' that they use to glue the two halves of my Jota engine together with in the factory. I used it when re-assembling the J motor and have had no problems what so ever. It was obtained for me by the previous owner using the five finger discount method but it's catalogue number is 23854.
It is known as flange sealant and comes in a mastic tube. 300ml.
It is also available in black (lucky for me)
Also works extremely well for 'D' rubbers and inlet manifolds onto head.

Barcode is 501266238548
IDH number is 142491 2211088
The above are for black

Not suitable for parts continually immersed in petrol


http://youtube.com/watch?v=mfmKkqLzHLk#

[kwaka]

Thanks zorded, i've already tried two different sealing compounds, Threebond 1194 and a GM threadsealer neither worked. i think i'll get some bolts and copper washers first off, failing that i'll give your method a go. I'm not sure what you meant when you wrote "coat the threads on the grub screws... with washers of either fibre or annealed copper".
Anyway a warning to anyone who thinks it might be a good idea to drill such holes to facilitate cleaning the head after bead blasting. DON'T DO IT.

[Al]

Sorry KWAKA, it was meant to be a list and should have read; and.

ie. plug the bottoms of the holes with 5910 and also coat the threads of the grub screws before you wind them in.

And; better still coat the threads of some socket cap bolts

And; better still put fibre or annealed copper washers under the threads of the socket caps with 5910 on the threads before you wind them in.

Hope this clears it up.



http://youtube.com/watch?v=mfmKkqLzHLk#