Has anyone who has worked on these non-unit 8 bolt bikes relate over torquing the head bolts with all of the cracks that develop in these heads, or is it just me? Structurally the rocker boxes, and especially the heads, are pretty close to the edge of what will work. Additional stress, from over tightening the head bolts, is not going to do them any favors. 25 foot pounds wet would be like nearly 30 dry depending on what you are using for a lubricant.
The Triumph Workshop manual
for Models 1945 to 1955 lists the head torque
at 18 pounds with a warning that "if tightened beyond this figure distortion may take place." Even the old No. 17 Triumph Instruction manual
(for non-unit) lists the head bolt torque
as 18 pounds.
Using 3/8 in. bolts in this application, and a rather fragile aluminum head and rocker box, there would be no way that you could get any bolt stretch before the aluminum was compromised.
As threads mate to each other with use, you get more clamping force for a given amount of torque
. Get out the old ARP hardware technical guide and read about retightening hardware numerous times before the final torque
is taken. ARP has you tightening the rod bolt nuts 6 times, and each time for a given torque
the bolt stretch increases until it settles down on about the 5th or 6th tightening. So over time, as these bikes are rebuilt and the reads worn in, the 18 pounds of torque
will provide more clamping force than the first time the head was torqued. No need for lubrication. And no, you are not wearing out those 3/8" head bolts as they are over kill for the application.
Bill, we have come a long way with rocker box gaskets. You need to try one of our new ones! It's like running no gasket, but they are a gaskets. Go figure! PM me and I will send you a sample... you'll like them!