Series 81 Torque Specs

Mike, I am looking for the same information. So far no one has a provided a number, but, I have been instucted to start in the center of the head and work out in a circular pattern. Also, since the head is aluminum, tighten in smaller steps than you would with a cast iron head. So far, the information I have found says heads should be tighted “firmly”” which doesn’t help much either does it?”

The specs for a 1929/30 iron heads are 60 ft lbs. Most PA guys use 65 ft lbs. We are told:

* use a circular pattern from center out

* Clean threads and use new bolts

* Use a special non sieze compound on the threads

* Tighten when engine cold – do not tighten when hot

* Run engine and let cool down then tighten again.

I am not an expert on this. Others may have some suggetions.

Correct head gasket very inportant.

Mike,

For your aluminum head (correct for all Series 81 and for the last 600 Series 80s), I’d go 5 lbs below that recommended for iron heads. For my two S80s with iron heads, I use 60-65.

For both, it’s important to use a dental pick or similar tool to clean and debris from around the base of the studs where they emerge from the block, so that the gasket will seat well in those areas. I also use an aerosol copper coating on both sides of the head gasket.

Torque pattern: No specific pattern was recommended in those years. I start with the center stud in the center longitudinal row, then the two outside studs (left and right) adjacent to the first one. The next two are the center-row studs just outboard, front and rear. Then I go diagonally (e.g., right rear, left front, left rear, right front) adjoining the two center studs just torqued. Use the latter technique for the remaining studs. I may be ‘way too particular, but my first pass is at 35 lbs/ft, then 45, then in 5-lb increments from there. Do the final torque reading (55/60, as you prefer–but no more than 60), TWICE.

Note well Bill Rolapp’s comment: Never re-torque when engine is hot–re-torque only when the engine has cooled sufficiently so that it’s not uncomfortable to put the palm of your hand on the head for 10 seconds. I prefer to re-torque at least three times, and you will still get some movement of the nuts on the 3rd re-torque.

George