SKU: 44455937608

ARP Head Stud/Bolt Kits

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Description

ARP Head Stud/Bolt KitsIt is for good reason that virtually every top professional engine builder relies on ARP Pro Series head studs for their all out competition powerplants. Simply stated, theres not a better stud setup on the market today. For openers, ARP uses a premium grade 8740 alloy that is rated far superior to aircraft quality. Each stud is placed vertically in special racks and precisely heat treated to 200,000 psi. This procedure ensures complete heat

It is for good reason that virtually every top professional engine builder relies on ARP Pro Series head studs for their all-out competition powerplants. Simply stated, there’s not a better stud setup on the market today.

For openers, ARP uses a premium grade 8740 alloy that is rated far superior to “aircraft” quality. Each stud is placed vertically in special racks and precisely heat-treated to 200,000 psi. This procedure ensures complete heat penetration and the results are far superior to those lesser quality studs from other manufacturers who just dump pieces in a basket and hope for the best.

Following heat-treat, 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 (a very common industry practice). It costs a lot more to do it this way, because it’s tough on tooling, but the results are well worth the extra effort.

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 – and one that compensates for head gasket compression when the cylinder heads are installed. This helps prevent blown head gaskets, and assures optimum engine sealing!

Premium quality heat-treated 8740 chrome moly steel head stud kits are available for most every domestic and import applications.

You won’t find a better quality stud on the market from any other source. Look for ARP stamped on each stud as your assurance of quality.

Clearly, ARP Head Stud/Bolt Kits are the best on the market today, and the favorite of leading professional engine builders in all forms of racing.

HIGH PERFORMANCE SERIES
High Performance head bolts are available with a reduced wrenching hex or 12-point and wide area flanged head that eliminates the need for valve train removal to facilitate cylinder head retorquing. All High Performance Series bolts are 180,000 psi (which is 15% stronger than Grade 8) and kits come complete with hardened parallel-ground washers.

PRO SERIES
All Pro Series bolts are cold-forged to ensure molecular integrity, heat-treated prior to thread rolling and machining, and are rated nominally at 200,000 psi. ARP Pro Series head bolt kits are application specific – designed for use with typically competition only components. These fasteners deliver superior strength and meet the ARP “ZERO defect – ZERO failure” quality standard. Hardened and parallel-ground washers are included with each kit to ensure even load distribution and accurate torque readings. All Pro Series head bolts have a reduced wrenching hex or 12-point head and wide area flange to eliminate the need for valve train removal for cylinder head retorquing and permits the use of larger diameter valve springs. Most applications have undercut short bolts that can help eliminate head gasket failures through providing more “stretch” to compensate for the additional compression of gaskets.

CUSTOM AGE 625 PLUS®

This newly formulated super-alloy demonstrates superior fatigue cycle life, tensile strength and toughness – with complete resistance to atmospheric corrosion and oxidation. ARP is the first to develop manufacturing and testing processes for fasteners with Custom Age 625+. Best of all it is less expensive and expected to soon replace MP-35 as the material of choice in the high strength, super-alloy field. Typical tensile strength is 260,000-280,000 psi.

 

Head Studs vs Bolts
On many street-driven vehicles, where master cylinders and other items protrude into the engine compartment, it’s probably necessary to use head bolts so that the cylinder heads can be removed with the engine in the car.

For most applications, however, studs are recommended. And for good reason. Using studs will make it much easier to assemble an engine (especially a racing powerplant which must be serviced frequently and quickly!) with the cylinder head and gasket assured of proper alignment.

Studs also provide more accurate and consistent torque loading. Here’s why. When you use bolts to secure the head, the fastener is actually being “twisted” while it’s being torqued to the proper reading. Accordingly, the bolt is reacting to two different forces simultaneously. A stud should be installed in a “relaxed” mode – never crank it in tightly using a jammed nut.

If everything is right, the stud should be installed finger tight. Then, when applying torque to the nut, the stud will stretch only on the vertical axis. Remember, an undercut shorter stud will have a rate similar to a longer, standard shank stud. This provides a more even clamping force on the head. Because the head gasket will compress upon initial torquing, make sure studs and bolts are re-torqued after the engine has been run.

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Exchange/Return Notes
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SKU: 44455937608

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4.6 ★★★★★
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Verified Purchase
Deholle
Natrona Heights, US
★★★★★ 4
Tuffy Desert Phrog vs Lola
Color: Green Leaping Phrog, Color: Green Leaping Phrog
Just a little background about my dog. Lola is a 5 year old corgi-terrier mix with jaws of steal. Lesser stuffed toys have met death in under 5 minutes. Tennis balls last less than a day. Rope toys that do not have frayed ends might possibly last a week (frayed ends never stand a chance). The only toys that she has not managed to destroy are her Kong, a Kong bone, and a racquet ball. I figured I would document the life span of Phrog (Tuffy Scale: 9) before making my final judgement on it’s durability. Day 1 - Phrog Arrives! Lola was very excited about the arrival of Phrog and immediately went into destruction mode. Phrog did sustain a little damage before we were able to bribe her to drop Phrog and get her understand that he was more fun to play fetch with than to mutilate. The white you see in the picture is not stuffing, but the second layer of defense for the toy. The fact that my living room is not full of stuffing and I didn’t have to pry a squeaker out of my dog’s mouth, I’d say Phrog wins the Day 1 challenge. Day 9 - Phrog has sustained a little more damage, but not anything life threatening. His side wound is a little bit larger and one of his eyes is half ripped off. For safety reasons, I am going to finish removing the damaged eye and some loose thread from various places. Other than that, Phrog is still holding up and holds top toy spot. I have also found him very useful for dealing with anxiety; the squeaker can often distract her from her stressors and Phrog takes the abuse of her frustrations. Day 16 - Phrog is starting to show signs of mortal wounds. Lola has made it through the thicker layer around his arm and I can see the stuffing. It is only a matter of time before gets all the way through. Day 60 - Phrog still lives!!! I have done some surgery on Phrog to reinforce the fabric around his arms, but Franken-Phrog is still the favorite of all of the toys. She will even get brave enough to rescue Phrog from the evil vacuum when he is kidnapped and tortured. I am thinking about purchasing Phrog II for the inevitable day when Phrog goes off to the pet toyland in the sky, but for now, there is only one Phrog for Lola.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on July 6, 2018
M
Verified Purchase
michael parsley
New York, US
★★★★★ 5
Super tough
Color: Red Warthog
My dogs love these toys!!!
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Reviewed in the United States on February 10, 2026
A
Verified Purchase
Amazon Customer
Boise, US
★★★★★ 5
Long lasting play toy!
Color: Multicolor
Tuffy toys in general are great and they are a pretty good deal on Amazon. They are not indestructible, and if your dogs use them as chew toys they will eventually break through. My dogs have had this Armadillo since Christmas (and they do chew on it some) and the only thing missing is an ear. They like to play tug-of-war with it a lot. This is a bigger toy, but even my forty pound dog plays with it. I would not recommend this toy for dogs smaller than Border Collie size. You can make these Tuffy toys last longer if you don't allow your dogs to chew them--when your dogs starts chewing on non-chew toys trade them for a chew toy and when you catch your dog chewing on a chew-approved toy reward them for chewing. Eventually your dog will catch on and realize that if they want to chew there are certain toys that are allowed for that. In addition to being a great play toy this is a pretty cute toy too!
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Reviewed in the United States on June 30, 2015
A
Verified Purchase
Amazon Customer
Chelsea, US
★★★★★ 1
Not Tuff
Color: Black Yellow Phrog, Color: Black Yellow Phrog
Absolutely terrible and not “tuff” at all. My chocolate lab had this thing destroyed in less than two hours. I would not recommend these for the price.
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Reviewed in the United States on April 11, 2026
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Verified Purchase
Carrie Ann Moore
Massapequa, US
★★★★★ 3
Cute but Not Durable
Color: 2PK Green Leaping Phrog
⭐️⭐️⭐️⭐️ Cute but Not Durable Super cute toy—my dogs loved it right away! Unfortunately, they chewed the head off within a few hours. I ordered a second one because they were so into it, but the same thing happened again. I won’t be ordering a third, but they still play with their two headless frogs. So while it’s not the most durable, it definitely kept them entertained!
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Reviewed in the United States on June 9, 2025

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