Quote:
Originally Posted by Fixer
This is a very important subject Jonny042 we need to protect our buddies so their hard work is ruined over an oversight by ARP. I'm not looking for any notoriety lol.
Matt
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Absolutely!!! Like I said, thanks for sharing the correspondence and for bringing this up.
I do share your concern about that 38 pounds!!!
One of the things I learned in my research on the topic which I found counterintuitive is that the same torque on a fine thread and coarse thread will result in a relatively similar clamp load on the fastener (in our case the head studs). Not the same, but somewhere in the range of 10-15% greater for the fine thread.
This is relevant because Henry Schmidt who's done a great job designing his Supertec head studs (with fine threads on the nut end) specifies varying torques for them depending on application:
Quote:
Originally Posted by Henry Schmidt
SUPERTEC PERFORMANCE HEAD STUD KIT INSTALLATION INSTRUCTIONS
1) USE BLUE LOCTITE ON CASE END (10 x 1.50)
2) WE SUPPLY SUPERTEC THREAD LUBE WITH EACH KIT BUT YOU CAN USE LIGHT
WEIGHT MOTOR OIL OR ANTI SEIZE ON CYLINDER HEAD END
3) CLEAN CASE THREADS COMPLETELY
We recommend a thread forming tap (1.50x10 PD-6 6-N) for this application
4) TO INSTALL STUDS, DOUBLE NUT WITH THE GOLD NUTS PROVIDED
5) INSTALL STUD UNTIL IT BOTTOMS AND TURN OUT 1/4 TURN
******DO NOT FORCE THE STUDS INTO THE CASE*******
6) INSTALLATION LENGTH IS NO LONGER RELEVANT
TORQUE SPECIFICATION + or – 2lbs STANDARD TORQUE PATTERN IS MAINTAINED
a. 2.0 aluminum case 30 lb/ft
b. 2.0, 2.2, 2.4, 2.7 ( all magnesium cases ) 26 lb/ft
c. 3.0, 3.2, 3.6 aluminum case 30 lb/ft
d. 3.0, 3.3, 3.6 aluminum Turbo 32-36 lb/ft
THERE IS NO RETORQUING NECESSARY
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So even though the ARP nuts are coarse threads and the Supertec are fine, the torque values would be somewhat comparable, keeping in mind the 10-15% difference.
In my application 30 ft/lbs would be recommended for the Supertec studs. To get a similar clamp load (of course that would depend on all things being equal which they rarely are, but given the lube provided with both studs they should be similar) you would need a bit more torque on a coarse nut.
So, I chose 32 ft/lbs. I wanted a slightly higher clamp than stock due to the plain sealing surface on the 3.2 Carrera cylinders in the motor I was building.
Given the new information from ARP I will use the same for the 3.4 I'm gathering parts for now. Already have the ARP studs I was really happy with them in the last build. Some things are subjective and intangible (like your testing!) but they just "felt" right going together.