Quick oil cooler question

[John Brooks]

That's a high torque fastener, it is cupped to keep the driver centered as you screw it. A big flat screw driver will damage the slot. P74 or aerospace tool. See link
viewtopic.php?f=1&t=42567&hilit=Torque

[WilliamVaughan]

The retainer plugs for the pressure relief valve springs can also be replaced with a hex-head style plug. I got them from Stoddard. I got tired of messing with the screw driver slot while trying to produce an appropriate crush of the sealing ring.

[Gary Koehler]

John,

If these screws are hi torque fasteners, what torque value is it that you recommend? The seals for both these fasteners in both my engines have copper "o rings", that is, they are tubular in nature before compressing and when partially compressed they store sealing energy as an O-ring does so the energy stored in that compression makes the seal and with this method it doesn't need to be high torque, in fact overtorquing would compress seal flat as they appear to be when they are removed.
And if they were hi torque fasteners, the factory likely would not have put a slot in the screw heads in the first place.
So please give me the torque values that you have for these, I can't find one.

BTW, a simple washer tapped into the slot with a light tap fit will not slip when torquing. Wilhoit still offers these in the original slotted configuration, they appear to have tubular seals. If anyone could improve them he certainly would be the person

[John Brooks]

Gary

I can't find a specific torque for the "control valve covers" in the 356 Manual SE17 or (15 EN Pg E31) and the 912 E105 or (19EN pg 42). It shows the spring tension, and just calls for a new washer. Both manuals and Elfring does call for the P-Tool P 74.

The term Hi-Torque is the "head design" (like Philips or cheese head). It was designed for the aerospace applications in the 50's. It was usually applied to shoulder bolts and flush countersunk bolts in high shear load conditions. It is designed to keep the driver "centered" in the slot even is the driver is not perfectly perpendicular to the fastener. The slot has a curved bottom, so as you push it in, it locates the fastener center, and as "rotational force" is applied, it is rotated from the center line of the hole bore. Similar to a Dzuse faster tool.
https://encrypted-tbn0.gstatic.com/imag ... qMFy1KkumN

As for a specific torque, I was taught to snug it flush and then add 1/8 turn turn to crush the round copper seal.. Maybe Vic or Jim can or some one that does allot of engines can chime in on a value they use. Even the Maestro neglects a torque value, he said "snug"

[Sean M Rooks]

Sean,

About that big-ass slot in the screw head: find your self a big-ass washer that's a couple of thou. wider than the slot, file a flat so that it enters full depth, chamfer the edges and and tap it in. It'll stay there until you re-install the screw. Then just tap it lengthwise in the slot and it'll pop right out. If the slot is buggered it may also smooth that out as well.

Brilliant! And thank you for the chuckle.

[Gary Koehler]

John,
I was messaged privately that it was 30-35 ft lb, not sure it is correct tho. I also use the 'turn of the screw method' - knowing the pitch gives a rotation value for the amount of crush I want to compress the CU ring, instead of using torque value.