Pulling Head Studs - ARP Finding

[Drbraunsr]

Attaching a link:Damage Alert: How to Avoid Pulling Threads or Killing Head Bolts

The smooth CNC of head stud pockets lets the washer act as a bearing and creates a possible over-torque situation. Solution is to sand (60grit) the one washer face to roughen up the bottom to prevent washer rotation. Also to only apply the Ultra Torque lubricant between the nut and the washer top.

Seems very reasonable. Gonna call the ARP tech folks and confirm

[SalParadise]

Great read. Thanks for posting this. It makes complete sense - and one that can be applied here and save a lot of people a headache - especially when considering the torque of 23-26 ft pounds on the head studs of an aircooled 911 engine.

[KTL]

It's been known for quite a while now that the ARP studs are a good stud in terms of their quality.
But they don't perform well when it comes to maintaining the clamping load. Here's a recent mention of it and notice the last post where Mark says he chooses not to use the ultra slick moly lube and the nuts no longer loosen up in operation

heads coming loose on 3.3 turbo motor

[1979-930]

Ha! Well I guess my being too cheap to use their lube has been a blessing in disguise.

[Drbraunsr]

ARP tech support did say:

-- a rotating washer should be avoided
-- the area between the aluminum head and washer face should be dry, no lube.
-- nut and washer top. yes, lubed
-- probably not an issue with my older air cooled 911, but no harm to perform the roughing up

[KTL]

Yeah I haven't looked at a head for a few weeks but I seem to recall the seating surface for the washers is slightly rough cast and certainly not machined.

Ideally it seems like the big thick washers for our heads should be serrated on the back side. I rub them on a sheet of wet sand paper to knock off the rust and make sure they're flat. I'll be sure to leave the head contact side rough with coarse grit paper!