I was just wondering if any one has researched or done any testing using studs and nuts instead of bolts on the m20 cylinder heads. My head bolts need replacing and i thing studs my help reduce wear on the barrel threads and gasket failure.

I found the comment below on a web site.


By contrast, a head stud can be tightened into place without any direct clamping force applied through the tightening. A stud can be threaded into a slot up to “finger tightness,” or the degree to which it would be tightened by hand. Afterward, the cylinder head is installed and a nut is torqued into place against the stud. The nut torque provides the clamping force, rather than the torque of the fastener itself, and the rotational force is avoided entirely. Because the stud is torqued from a relaxed state, the pressure from the nut will make it stretch only along the vertical axis without a concurrent twisting load. The result is a more evenly distributed and accurate torque load compared to that of the head bolt. This ultimately translates into higher reliability and a lower chance of head gasket failure.

Cheers
Phil Smith
NZ

email (option): wpgarage@xtra.co.nz

It sounds good but I would question the mechanics of the assumed reduced loading on the stud...

However, both methods will work OK in practice and both methods are used on various engines...(BSA, bolts, Norton, studs for example)

If a change to studs is contemplated then the studs must be manufactured from high tensile steel and the nuts should have a length of 1 1/2 to 2 times the thread diameter...I would go with 2 times personally...

I do have an M20 barrel in my pile of bits that has had studs fitted...

The thread into the barrel is 3/8" BSF...Torque bolts/nuts to 28/30 psi and use a solid copper head gasket..

I preempted thread problems on my own M20 by helicoiling the barrel threads from the outset and have never had gasket failure problems since adopting a torque setting and solid copper head gasket a number of years ago...Ian

email (option): ian@wright52.plus.com

The comment on studs is quite valid. In addition, you can use the entire thread in the head, hence less thread stress.
On these old machines, the bolts are often ropey and tight in the threads. If they have been replaced in the past, they may also be too short. I get high tensile threaded rod and make up my own studs. I use thick washers and make sure the nuts are free on the threads. It does not matter if the studs are tight in the head.
I use a solid copper gasket, and tighten the nuts by feel in very small increments, about half a flat at a timep, and in rotational sequence. I believe that this ensures a better incremental compression and final fit of the softened copper gasket, than using an opposite/diagonal tighening sequence.

email (option): pvlietstra@gmail.com

['I use a solid copper gasket, and tighten the nuts by feel in very small increments, about half a flat at a time, and in rotational sequence. I believe that this ensures a better incremental compression and final fit of the softened copper gasket, than using an opposite/diagonal tighening sequence.']

It is interesting that different manufacturers recommend different sequences for tightening cylinder head fastenings...BSA and Norton for example work basically in the opposite direction...

This indicates the exact sequence is probably not the most important factor, rather it is more important to tighten them incrementally and evenly as mentioned....

I used to tighten them by 'feel' but these days use a good quality torque wrench where the desired setting is roughly at the mid point of the wrenches range...This ensures more consistent accuracy...

If using a torque wrench do not use copper grease, moly grease or similar...Just some very light machine oil...Ian

email (option): ian@wright52.plus.com

Great comments and all taken on board thank you very much for fantastic sorce of information. I will post some pics soon.
Cheers
Phil (From the other side of the planet)
NZ