Head Torque Values for ARP Head Studs

[aws]

I just got off the phone with ARP and the recommended torque for their head studs is 38 foot pounds. I am building an early aluminum case engine and that torque number makes me nervous. Has anybody had experience using that high of torque on the early aluminum case?


aws

[Steve@Rennsport]

FWIW,....ARP uses a different alloy & thread pitch and I would follow their recommendations.

We now only use factory 993 TT ones,...

[Henry Schmidt]

Originally Posted by Steve@Rennsport

FWIW,....ARP uses a different alloy & thread pitch and I would follow their recommendations.

We now only use factory 993 TT ones,...

FWIW: The only head studs on the market today that varies thread pitch based on application are the Supertec Head studs.
10X1.5 on the case end and 10x1.25 on the nut end.
This design is used on every high performance fastener application I have ever encountered except Porsche. RR, Hewland, Cosworth, Lycolming, NPTI and the list goes on.

ARP uses the inferior thread design (10x1.5 pitch on both ends) just like all the Porsche factory stud designs.

[aws]

Henry, what are the torque specs on the Supertec studs? The ARP studs are austenitic and appear to be stainless. My concern is that with expansion the 38lb torque value will go up high enough to pull the aluminum threads in the case.
I am sure Porsche went to the finer thread on the thru bolts for more even torque application and I can see where that would apply to the head nut end on the Supertec studs.

aws

[Henry Schmidt]

INSTALLATION INSTRUCTION
1) USE BLUE LOCTITE ON CASE END (10 x 1.50)
2) USE LIGHT WIEGHT MOTOR OIL OR ANTI SEIZE ON NUT END
3) CLEAN CASE THREADS WITH BOTTLE BRUSH OR 10 X 1.50
THREAD CHASER (DO NOT USE TAP)
4) USE GOLD NUTS ON STUD AS INSTALLATION TOOL (LOCK ONE ON TOP OF THE OTHER).
5) INSTALL STUD UNTIL IT BOTTOMS AND TURN OUT 1/4 TURN
6) INSTALLATION LENGTH IS NO LONGER IMPORTANT

TORQUE SPECIFICATION + or – 2lbs STANDARD TORQUE PATERN IS MAINTAINED
a) 2.0 aluminum case 32 lbs
b) 2.0, 2.2, 2.4, 2.7 ( all magnesium cases ) 26 lbs
c) 3.0, 3.2, 3.6 aluminum case 32 lbs
d) 3.0, 3.3, 3.6 aluminum Turbo 34-36 lbs
THERE IS NO RETORQUING NECESSARY