[Fot] Head torquing

[Greg Solow]

First make sure the head and block surfaces are clean and flat and that all 
of the threaded holes in the block have good clean threads.  With studs, 
screw in the studs hand tight only. Do not tighten studs into a block unless 
you are sure that the bottom of the stud can hit the bottom of the hole.  On 
a TR4 type engine, the studs do not have as long a bottom as the hole is 
deep, the stud will thread into the block stop where the threads on the stud 
end. If you continue to torque the stud into the block, the threads will try 
to pull the stud down into the hole and the stud will act like a wedge. It 
will cause the block to crack from the stud hole to whatever the nearest 
open area is.  This is the reason most "tractor" blocks have cracks at the 
left rear stud hole going to the water jacket.  There are improvements to be 
made here, but that is another storey. So just tighten the studs hand tight. 
We have found  Permetex "Anti-Seize" when used as a lubricant on the head 
bolt thread, washers and nuts, does not change the torque that is applied, 
but does help prevent the "sticktion" mentioned in the earlier posts, so 
that it becomes less necessary to loosen the nuts first during retorquing. 
So on a TR-4, we apply the anti- seize to the fine threads on the top of the 
stud, to the top surface of the washer and to the inside of the nut and its' 
bottom surface. Tighten the nuts using a normal torquing sequence to about 
30 lbs. ft., then 50, then 70, then we go to 85 or 90.  We use this as a 
maximum torque.  WE no longer torque heads to 105 lbs. ft. as we have not 
found it necessary, and it only leads to broken and stripped studs and head 
nuts. Run the engine to get it fully up to operating temperature, then 
retorque the head hot, to the same torque figure as the initial torque. 
With a solid steel head gasket, you can try again, but we have found nothing 
will tighten any more. With a composite (copper/asbestos) or other "non 
solid sheet" gasket, we hold retorque the head again after a couple of heat 
cycles.  If you wish to loosen each nut before retorqing, there is certainly 
no harm in doing so. It is good to mark each nut with a scribed line before 
you loosen it up, so you can tell if it tightened to a position that is 
tighter than it was in the begining.  If I try to tighten a nut or stud, and 
it will not move, then it is definitely good practice to loosen and then 
retorque.
    These general instructions ( except for the torque figures quoted) will 
hold true for any cast iron block and head combination.
    Using ARP moly based assembly lube paste on the head nuts and studs will 
require a reduction in torque of over 30% because it is so slippery. We have 
tried using the ARP lube and one time actually crushed the raised boss on a 
TR-4 head above the intake ports.  The Anti-Seize works very well.  On 
modern engines the manufacturers no longer (generally) use torque figures 
for head  tightening. The engineers have calculated how much "stretch" on 
the head bolts they need to get the clamping pressure  on the head gasket 
that they want, & the procedure is to torque to 20 lbs, ft.or less,  then 
use a protractor and tighten the bolt a certain number of degrees from that 
point, the desired preload is calculated by the pitch of the threads of the 
bolt. This procedure avoids the variables caused by the friction of the bolt 
or nut on the threads or the washer and achieves a more consistent clamping 
force on the gasket.
                                                                             
                    Greg Solow