Jupiter head bolt stripped

[Forumadmin]

Hi,
Last year on nipping my head bolts up tp correct torque (40lb) a bolt turned. Though no compression loss I am getting oil in the radiator but no water in the oil. I need to hellicoil. Do you know anyone who could do it for me or the size and source for buying the kit.
Cheers,
Tony Jackson N W Section
_________________
Member JCC and JOAC + Hare and Hounds mixed marque club

[Forumadmin]

I do not think a helicoil will solve this problem. I suspect some welding is necessary. Suggest you try a search on the web for suppliers of Helicoils or speak with some local engineers and aluminium welders. Classic Autos in Kings Langley are pretty good.

[ian Howell]

I have a 5/16" BSF Helicoil kit with a few inserts, available to club members for postage costs.

Ed Nankivell used it YEARS ago and the fix is of course still sound.

If the metal has stripped then a helicoil will fix it permanently. You may only need to remove the loosened stud and refit it using a sealant such as Hylomar.

Others may have a different view.

Watch this space.

[Drummond Black]

Tony, In your post you ommitted to say which stud turned. Oil in the water looks like it getting in under pressure. One theory is that it is coming in around the rocker feed stud. A bit more onfo might help.
Have you removed the offending head ??

Ian, Head studs are unfortunately 3/8 BSF.

Drummond

[aj4cks]

I have a 5/16" BSF Helicoil kit with a few inserts, available to club members for postage costs.

Ed Nankivell used it YEARS ago and the fix is of course still sound.

If the metal has stripped then a helicoil will fix it permanently. You may only need to remove the loosened stud and refit it using a sealant such as Hylomar.

Others may have a different view.

Watch this space.

Hi Ian whats Drummond saying about the kit? Would like to use it and happy to pay postage

[Tony Fearn]

Hello aj4cks,

I'm an 'aj c-l-m' in Lancashire.

Good to have you on JowettTalk. I see that it's your first post on this Forum. You will have noticed that most of us don't hide behind acronyms.

Are you an 'Anthony John' as well? If you are, then get in touch with the Webmaster and 'come out'. We'd love to know to whom we are talking.

Tony.

[aj4cks]

Thanks for the response Guys. I do not think its a corrosion isue that requires wealding as the engine was rebuilt by Mike Smailes 3 years ago. I wil recheck the studs on both heads but I think it was a middle stud. Though I can whip the heads off does any member know of a reliable garage or engineer that could do it for me? Drummond suggests that the helicoil kit I an has is the wrong size.
Hope to take the car to the National rally.
Cheers,
Tony Jackson

[Drummond Black]

Tony, After you said it may be the middle stud confirmed my original thought. Another question is what side is it that you feel is stripped ?? I went to the workshop and checked a few engine crankcases. The casting shape around that area looks meaty, however if a hairline crack appeared then oil could easily go into the water as this stud feeds oil to the rocker arms. The oil in this area is at engine oil pressure which is much higher than the pressure in the cooling system. From experience I would have thought that the rest of the head bolts would have held the cyl head gasket firmly to prevent the oil creeping along the casting face if you had only stripped the thread in the block. I could be totally wrong and only careful examination after removing the cylinder head could confirm this. If only the thread is stripped then helicoil is definately one solution. You will have to watch your drilling and tapping depths as there is a flared small copper pipe at the bottom of this stud hole which feeds the oil from the main oil gallery. The stud thread is 3/8BSF. One other option is to get a special stud made with a larger dia thread at the crankcase end. A bit more thought should into this option. You could move to a rougher thread ( BSW or Metric ).

As I say a lot of the above is asumption which would need careful checking. Others may have different thoughts that would be good to hear before you start stripping the head off.

Drummond

[Forumadmin]

I have suitable Helicoil kit you can borrow if that is what it turns out is required.

[Mike Allfrey]

I think my Technical Notes Series has been placed in the Jowett Gallery. Having never managed to get into that very secret domain, I can not be sure!

Reference; The Oil Feed Stud

I would never contemplate applying 40 lb.ft to that particular stud (Numbered '1' in the tightening sequence). Typically the thread engagement in the crankcase is much shorter than all of the other studs. This stud is usually tightened with a good quality open-end spanner.

I understand that Jowett Cars Limited made no mention about caution with respect to the oil feed stud. I learnt the hard way, stripping three studs out of the crankcase, in my youth, thinking that, being labelled '1' in the sequence, it should be tightened in the same manner as the other studs. I even made a distance collar so that it could be torqued without the rocker gear in place. Not a good idea!

I have similar qualms about the long centre stud, as during the tightening process, it can be felt to flex alarmingly!

With the cylinder liners seated on solid copper spacers and shims, at 0.006" protrusion, I never tighten to 40 lb.ft. I use 35 - 37 lb.ft, maximum, and have had complete success with that setting. The club should have a campaign of blacking-out the original Jowett specification and inserting the revised specification in all service manuals.

Reference: The Use Of Helicoils (Re-coils)

Typically, a Helicoil is too short for use in a Jowett crankcase. This is very strange, as the prime use for Helicoils is in aluminium castings where deeper threads are the norm.

In the case of cylinder head stud threads, I use two helicoils, one on top of the other. This requires care in installation, but it can be done. What needs to be watched is that the second coil does not wind into the initially threaded-in coil. I have a 3/8" BSF Allen socket-head grub screw that I screw into the first coil, so that it is flush with the tail of the first coil and then thread in the second coil with its special tool, as far as the grub screw.

A very important point, Be extremely careful when tapping out the thread for the coil, that it is at right angles, from all directions, to the cylinder head gasket surface. It is very tempting to 'bend' a cylinder head stud so that it can be aligned -- this practice can prove to be very expensive!

Maybe, in England, longer Helicoils are available? They are not here in OZ.

I hope this helps a little.

Mike Allfrey.

[ian Howell]

When I was selling Helicoils (many years ago) they were available in multiples of their nominal diameter, e.g. 5/8" for a 5/16" BSF Helicoil, and I think they went up to 3 x diameter.

In aluminium, 1 1/2 x diameter is strong enough to enable a high tensile Allen headed bolt to be sheared - a most impressive demonstration!

This is because the Helicoil can move within the new threaded hole and so spread the load over its entire length.

Also, having sheared off the Allen headed bolt, it was then possible to unscrew the sheared-off stump with your fingers because the thread had not been damaged.

I don't see any reason why putting two into a suitably deep re-tapped hole would cause problems.

[PJGD]

I have had luck with the WTI thread inserts.

I suggest dowloading the catalogue from: www.wireinserts.com

Philip Dingle