cylinder head bolts and studs

[new to this]

this may be an odd question but why do they have studs on the cylinder head,could they not be replaced with bolts

dave

[jleyton]

Not an odd question at all Dave - it's a damn good one and one I have often wondered about myself.

It has been discussed on here before but, for the life of me, I can't remember the collective wisdom or opinion on the subject

I am also sure that there was some supposedly cunning reason for the studs being fitted at a different angle to the bolts but, once again, I am at a loss as to why

Like you, I'll be very interested to hear the replies and I'm just sorry that I haven't got any myself

Cheers

Julian

Ps I'd also be interested to know why the studs frequently get stuck whereas I think it's fairly rare for the bolts to do so !

[jbuckl]

IIRC Dennis Barbet, Ex triumph test (sp?) told me the studs were angled as a design specification...... from...... service(!)

So that access was possible to remove the heads without removing the cams (rope trick needs them out though!!!!)

Otherwise the fasteners would have had to have been accessed from under the cams.

They may have been chosen to be non standard studs as opposed to non standard bolts as studs would be auto turned bar & cheaper than anything hex headed.


So perhaps that decision cost the whole of the british car industry?


Bear in mind though, that the design was outsourced.....maybe that was the actual cause?


(outsourcing is still causing similar things to happen today imho)

[V Mad]

Good question Dave. I would say it's because there would be too much twist throughout the length of the bolt, and the applied torque would not all translate to the threaded end. Thats not a very good explanation though, I will have to think about it.

Re Julians point:
"Ps I'd also be interested to know why the studs frequently get stuck whereas I think it's fairly rare for the bolts to do so !"

Its a combination of things: the bolts are waisted, so there is more clearance, plus the bolts are shorter so less to bind. I dont know why they dont make the studs waisted; I suspect it is a cost issue.

[jbuckl]

I think ej ward did get some sets of motorsport waisted studs.

The studs do seem to get closer to the drillings than the bolts....but that could be 'runout' on the threads being worse than intended.

[new to this]

julian

not sure on this ? but think there is more clearance with a head bolt than a stud and thats why the studs get stuck

chris

not sure what you mean by bolts are waisted ?

dave

[jleyton]

chris

not sure what you mean by bolts are waisted ?

dave

Bit like this Dave.

I used to have a waist, but not these days

Cheers

Julian

bolts_with_waisted_shank_05_0.jpg

[new to this]

Bit like this Dave.

I used to have a waist, but not these days

Cheers

Julian

[ATTACH=CONFIG]21625[/ATTACH]

but they don't sell pop belly bolts any more

dave

[Seaking]

Took this from Arp site i believe the super charged stag uses the TR7 set x2 3. Do the head studs only go in hand tight?

The studs should be installed finger tight. Then, when applying torque to the nut, the stud will stretch only on the vertical axis. An undercut shorter stud will have a rate similar to a longer, standard shank stud. This provides a more even clamping force on the head. Because the head gasket will compress upon initial torquing, make sure studs (or bolts) are re-torqued after the engine has been run.

Cheers Glenn

[73 Mimosa]

Recent events have got me thinking about this insofar as can anything be done to get these studs moving before HGF occurs.
Maybe loosening them off one at a time and try and get it moving Plusgas etc.
I would be much happier if knew they were all mobile.
the chap who built the engine for me is very meticulous and I'm sure he copper greased them up but that was over 20 years ago.
I'm almost tempted to pull the heads off now for the next 10+ years piece of mind.

Or am I just PARANOID .......

[jleyton]

Or am I just PARANOID .......

Yes But I'm just the same

Cheers

Julian

[mike@thenook]

Recent events have got me thinking about this insofar as can anything be done to get these studs moving before HGF occurs.
Maybe loosening them off one at a time and try and get it moving Plusgas etc.
I would be much happier if knew they were all mobile.
the chap who built the engine for me is very meticulous and I'm sure he copper greased them up but that was over 20 years ago.
I'm almost tempted to pull the heads off now for the next 10+ years piece of mind.



Or am I just PARANOID .......

The two heads I just took off 20 years after I built my engine were fitted with nickel plated studs and all but one came out no problem with one having to be sawed through and one bolt which sheared.
I am sure the plating helps a great deal to keep corrosion at bay and I would think it would be quite a good idea to take each one out say every 3 years to keep them lubricated and movable but you would have to be very careful not to upset the head gasket seal in the process.

Cheers

[dasadrew]

Taken from a 1970 technical article on the Stag (and Saab 99) engine:

Head stud rationale.jpg.





















In other words, the tight tolerance between stud and head hole was chosen to enable the stud to exert a sideways force on the head as well as a clamping force, thus ensuring that the head doesn't move on the block due to its tilted angle.

[73 Mimosa]

The two heads I just took off 20 years after I built my engine were fitted with nickel plated studs and all but one came out no problem with one having to be sawed through and one bolt which sheared.

Thanks Mike that's encouraging

[StagnJag]

Recent events have got me thinking about this insofar as can anything be done to get these studs moving before HGF occurs.
Maybe loosening them off one at a time and try and get it moving Plusgas etc.
I would be much happier if knew they were all mobile.
the chap who built the engine for me is very meticulous and I'm sure he copper greased them up but that was over 20 years ago.
I'm almost tempted to pull the heads off now for the next 10+ years piece of mind.

Or am I just PARANOID .......

If you do go down that route and snap a stud while trying to free them up you will kick yourself. If it 'aint broke and all that!

Rgds

Dave