Triumph TR3 drawing


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Triumph head torquing

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.


I forgot to mention a couple of things. Make sure that the fine threads on the studs are not distorted. Wire brush them clean and then inspect them under bright light against a white wall. The threads should not tilt upward, but should be nice and uniform. After 50 years of head gasket replacements the threads will eventually become distorted and will bent upwards. Any studs like this should be discarded. Another way to check them is to take two studs and fit the threads together. Hold them up to the white wall and there should be no light visible between the threads of the two studs. If the threads of one stud are distorted, light will be visible. Check the bottom of each nut. feel the inside of the hole. The threads should not be pulled downwards. When a nut is machined, there is always a little bevel on the inside of the hole leading into the first thread. As the nuts are torque again and again, the thread will pull downwards. If these threads are distorted, discard the nuts. Replacing the nuts with good Grade 8 "high nuts" is a good idea. A "high nut" is a nut that is about 1 1/4 times taller than a normal nut of the same size. Curtiss Industries makes good ones that are heat treated to have a tensil strength of 180,000 psi. Lawson Industries also distributes similar nuts. Of course all ARP hardware is top notch, but I do not like the look of 12 point head nuts on a Vintage race car, they just don't look right. I do not believe that ARP make a hex "high nut" Finally make sure that the nuts will spin on to the studs easily with your fingers before using them.

Greg Solow

Just as a follow up, if you use the head studs as picking points to hoist the motor into the car, the threads can be easily dinged enough to skew the torque values. I use the ARP's but not to hoist from, I keep a pair of original studs for that purpose. I caught an episode of Horsepower TV last week when they did a test on ARP bolts with different lubricants and it's amazing the wild swings in torque you can get with the different lubricants. They sold me, nothing but ARP lube with ARP bolts.

Jim G.





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