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ARP
Diesel Head Studs |
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This
ARP head stud kit is made from 8740 chromemoly steel, 190,000 psi
tensile strength. It is precision centerless ground and thread rolled
to Mil-S-8879 specs. The kit includes black oxide finish studs, hardened
washers, and premium grade nuts.
Obtaining the optimum cylinder head-to-block sealing is especially
critical in small displacement engines employing high compression
pistons or power adders like turbochargers, nitrous oxide and superchargers.
That's why ARP® head studs are popular among leading Sport Compact/Import
racers.
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You
should know that ARP® uses a premium grade 8740 alloy that is
rated far superior to "aircraft" quality. Then, each stud
is precisely heat-treated to 200,000 psi. Following heattreat, each
stud is centerless ground to make it as close to perfectly concentric
as possible. This procedure involves about ten very slight cuts
and results in an exceptionally straight part. It's important to
note that lesser quality studs are not even centerless ground, the
material is thread rolled in bar stock form (mostly before heat-treat,
when the material is easier to machine). Because ARP® studs
are manufactured to such exacting tolerances, you will note that
gaskets and cylinder heads literally glide into position and are
perfectly aligned, something that won't happen with inferior quality
head studs.
ARP® studs
are thread rolled after heat-treat, which gives them about 1000%
(that's ten times) better fatigue strength than those studs that
are threaded prior to heat-treat.
You will also
note that ARP® offers specially undercut studs for several engines.
This procedure (done only to the shorter studs) more equalizes the
"stretch" of both studs, which makes for a more consistent
clamping force, one that compensates for head gasket compression
when the head is installed. This helps prevent blown head gaskets,
and assures optimum sealing!
Premium parallel
ground washers are also included with each kit. |
| TECH
TIPS: HEAD STUD INSTALLATIONS |
- Clean and
chase all bolt threads in block to ensure proper thread engagement
and accurate torque readings.
- All hardware
should be cleaned and inspected for possible shipping damage prior
to installation.
- Since most
studs extend into the water jacket, coat threads with ARP thread
sealer and screw in hand tight ONLY.
- Install gasket
and head, then lubricate washers and nuts with oil or ARP moly
assembly lubricant prior to their installation.
- Following
the engine manufacturer's torque pattern, torque each stud nut
three times to recommended values found in the general fastener
chart below.
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| NOTE:
To ensure positive sealing of "wet" head studs, a hardening
or semi-hardening sealant, such as Loc-Tite or Permatex, etc. should
be used. Some engine builders employ a sealer in the coolant, such
as Aluma-Seal, Silver Seal or K&W sealer, etc. You may also use
high temperature RTV silicone. Whatever product is used, it is imperative
that the cylinder head is installed and torqued to proper levels BEFORE
THE SEALANT HAS CURED! |
|
Torque
w/30-Wt Oil |
Torque
w/ARP Moly-Lube |
| 1/4in. stud |
12-15 |
10-12 |
| 5/16in. stud |
25-32 |
20-25 |
| 3/8in. stud |
45-56 |
35-44 |
| 7/16in. stud |
71-89 |
56-70 |
| 1/2in. stud |
108-135 |
84-105 |
| 9/16in. stud |
156-195 |
122-152 |
| 5/8in. stud |
214-268 |
167-208 |
| 6mm stud |
10 |
9 |
| 8mm stud |
25-32 |
20-25 |
| 10mm stud |
54-68 |
42-53 |
| 11mm stud |
80-100 |
63-79 |
| 12mm stud |
97-122 |
77-96 |
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