Time to reinstall my Testarossa heads. The manual calls for a specific head but tightening pattern, 50Nm, then a repeat at 110Nm. The nuts sit on top of thick washers. While the factory manual makes no mention of any lubricant or anti seize, the thought is to put a smear of anti seize on the studs so removal in 30 years is easier. My friends in Modena who rebuilt the heads suggested a tiny amount of grease on the threads. That would affect the torque figures. Any thoughts?
If grease is used it needs to be a very light, thin grease. Redline assembly lube would be OK. On the base where they screw into the block antisieze is good but the head nuts oil is better. I think 3 stages is far better then repeat max torque then a retorque in 1000 miles and retorque every 15,000.
Agreeing with above advice, because of different friction issues on applying torque, I try to identify the original lubricant usage at the time a factory manual was written. Failing identifying the lubricant used (or not), I use oil on the nut threads and some form of antisieze on block threads. I use 3 stages of torque application with a freshly-calibrated torque wrench. If the head and block are of similar material a later retorque should prove pointless, if materials are different the retorque described above is worthwhile. And I use washers of the specified hardness of the originals if the originals are not used again.
The old studs did not come out of the block, too much risk of damage. So, I will consider a small amount of assembly lube (I have some Amsoil). Factory manual is silent on lubrication. Probably not because it is to be avoided, but because they assume the mechanic knows this already. The three stage tightening process is a good idea. Interestingly, the specialist machinist shop in Modena (an incredible place to wander through if you like old F and L car engines) uses an Italian reference book from the 90s which specified 60 Nm then a 90 degree turn. I will get my torque wrench calibrated beforehand as well. Thanks to all.
For head bolts / studs+nuts, I generally use ARP assembly lube. Usually the +90 degree stuff has to do with pushing the fastener slightly past its elastic limit. I don't know the specifics for your motor, but I would want to find out if the studs can (or should) even be reused more than once. Ray
This isn't specific to Ferrari motors (which I know next to nothing about building), but just as a general guideline, here is what I have always done over the years: Re-torque: @ 500 miles (when I dump the engine break in oil) Re-torque: @ 1500 miles Re-torque @ 5000 miles After that, I check torque anytime I adjust the valves or am in the motor for some reason. I've had a few head bolts "move slightly" at the 1st and 2nd check, which is always mildly alarming. I don't care what anyone says about "you don't have to re-torque when using XYZ gasket" or whatever the F the story is - I check the torque multiple times until I'm fully convinced nothing is cinching down more. Tightening down a nut or bolt "a little more" is a world easier than blowing a head gasket and having to start over from square 1 again. Ray
The torque is mainly a measurement between the nut, washer, the part being fastened, and the stretch of the bolt or stud. Some oil or anti-seize on the threads is helpful and will not cause any significant change to the specified torque value. Unprotected steel and aluminum is prone to corrosion.
I have found over the years Ferrari studs are not great. In a number of cases, the studs take different degrees of rotation to achieve the same torque. I have had custom studs made by quality manufacture and they make all the difference. While this is not always financially feasible, I try not to reuse Ferrari head studs. If original replacements are available, I will use that and closely monitor the degree of rotation needed for the torque required. The last one I did (360) ended up with very good results. I used new studs, washers and nuts. I find it odd that on 355 & 360s the corner positions have an inadequate relief machined in the head for the size washer Ferrari uses. I believe this causes issues. The washers are forced into the head and I have had to go to great lengths to get the washers out of the recess. I will machine a small amount from the 8 corner washers to insure they don't bind. The last one (360) I had to hammer the washers from the head. You could see how the washers were only catching the edge of the recess. This one was the worst I had seen and the hardest to get the washers out. I have also found issues with the acorn style head nuts (308/Boxer/TR). I have had more than one that will bottom the nut on the stud before reaching proper torque. I always put the nuts on and measure the height and calculate the stack to be sure I have clamping not bottoming. I have used double washers to take care of the bottoming and had no issues with that solution. Just some of my experience. You experience may vary, some assembly required, batteries not included.
My experience in aerospace includes use of torque specs that have different values for lubed and dry fasteners/nuts, i.e. there is a significant change. YMMV.
I had an ARP catalog once and I recall that they recommend their own lubricant and not use oil (let alone dry fasteners). However, they did all the needed research to be able to define the required torque to get the fastener into its elastic pretension. Making the hardware like a preloaded spring to remain tight. It's not the clamped part in question which defines the required torque, it's the hardware. The reduction for using ARP lube vs oil (again, which they spoke against) was as much as 20 to 25%. Imagine the difference to dry hardware. Aluminium heads on ally block need to be retorqued. While I can only speak for one engine family, it won many endurance races in the 70s.
Thanks for the continued education. I can get a set of new studs, but at £1300 for the OEM set, it may be cost effective to seek better quality replacements. Who can make good studs for an old Ferrari? The idea of retorquing the nuts on the studs every once in a while makes sense to me; I assume you don’t pull the engine from the car every time? The process is not to loosen and retorque, rather just to ensure nothing is loose by applying the 110 Nm again to each nut in the same pattern?
I would check ARP's catalog and perhaps call them. There is nothing mystic about fasteners, but it is a sensitive topic. Imagine I advise to use ARP hardware instead of OEM and your head gasket burns through? You understand that a dry bolt/nut requires so much more torque to get into its proper range? That's why con rod bolts get torqued to length (stretch), not Nm or Lbft. And that is also why the industry went from max torque to a lower value, plus degrees. That is more accurate. For the ally Can-Am engines we loosen one nut at a time and retorque. The ones in the lifter/tappet galley are a pain because the intake has to come off. But there are ways around it. Your car's manual should tell you how to retorque. I have to refer you to it.
Fom ARP’s 2021 catalog, page 29: The Lubricant Is The Key A major factor that influences friction in a fastener is the lubricant used, and therefore influences the torque required for a particular installation. One of the most overlooked aspects of choosing a fastener assembly lubricant is…the lubricant’s ability to stabilize friction inherent in all high performance engine fasteners. As discussed earlier, friction is at its highest point when a new fastener is first tightened. This friction inhibits the fasteners ability to achieve the required clamp load on the first several cycles. In fact, ARP’s in-house Research and Development department has proven that new fasteners using motor oil and other commonly used lubricants such as Moly and EPL typically require 5-7 cycles before final torquing to level out the initial friction and achieve the required clamp load. Slicker lubricants may reduce the required torque by as much as 20-30% to achieve the desired clamp load, but compromise in areas of major importance such as repeatability, and may yield the fastener prematurely. Typically, the slicker the lubricant, the greater the clamp load scatter will be during installation.
Just to add another reference point - I reached out a friend in Modena who does this work for the factory on both newer and older cars. Factory practice is to tighten the nuts in a clean and dry condition.
