Head studs

Just wondering: any use to torque the head down to less than 30 pounds? Not uncommon
for brit bikes to ask for near 20.

I think that ‘stretch’ and ‘expansion’ are two separate properties aren’t they ?

Fast Eddie said:

I think that ‘stretch’ and ‘expansion’ are two separate properties aren’t they ?

Click to expand...

As effected by force and heat, respectively.

What I’m thinking is that regarding expansion: assuming the bolt has the same coeficient of expansion, then the clamping force when cold will remain constant as it heats and cools.

With stretch, the clamping force increases as things heat up and expand, but do so within the elastic properties of the material, and reduce / return to the pre set force when things cool.

It seems to me that stretch gives more safety margin against things like slightly under torqued fasteners.

This might not of great value for those fasteners that are easy to get at and will be checked by a conscientious owner (like Glen) but it seems to me to be of value for things like the through bolts...

I was looking for a cheap way out!

We don't really know if the high tensile stretch bolts stretch enough to keep up with an alloy barrel.
Even with the reduced sectional area, a high tensile bolt might still tear out those soft Al threads over time.
I like the SS for this as , in theory , the tension on the connection should only increase slightly during a heat cycle. The factors are 17.4 for Ss to 19 for A132 Al. casting alloy. Grade 8 bolts are somewhere around 10-11.
It's a lot of guesswork with an alloy 920, there just aren't many long term succesful ones out there. That's why I thought it best to do things slightly differently.
The two changes I have made are the bolts and the increased interference fit of the liners.
It's an experiment.

Glen

Another option (or along with the reduced shanks) is thick conical spring washers. .080" thick 3/8" belleville spring washers are available from Mcmaster carr part # 9294K61 You can stack them to get the pressure you want.