01-25-2020, 11:23 AM | #1 |
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ARP head studs
Picked up an ARP catalog at the GNRS and see that they have a head stud kit for the Model A with polished SS acorn nuts and washers. Part number is 151-4002.
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01-25-2020, 12:02 PM | #2 |
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Re: ARP head studs
Does the catalog show the price? ARP are the best but a bit on the expensive side.
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01-25-2020, 09:40 PM | #3 |
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Re: ARP head studs
That kit # hasn't hit the on-line catalog yet.
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01-29-2020, 08:01 PM | #4 |
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Re: ARP head studs
Weird, I have a saved electronic copy of a 2017 catalog with it in it, and I have been looking at it online in their 2020 catalog for at least the last 2 weeks now. I saw it and pointed it out to a friend of mine.
*edit* I emailed Summit Racing to get pricing on the kit as I don't see it listed anywhere online. Last edited by Chad Marchees; 01-29-2020 at 08:19 PM. |
01-30-2020, 12:26 AM | #5 |
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Re: ARP head studs
Might also try Reds Headers, they carry ARP now also.
http://www.reds-headers.com/html/contact_us.html
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01-30-2020, 11:39 AM | #6 |
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Re: ARP head studs
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01-30-2020, 11:56 AM | #7 |
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Re: ARP head studs
Because I run high performance engines!
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01-30-2020, 08:05 PM | #8 | |
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Re: ARP head studs
Quote:
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01-30-2020, 11:30 PM | #9 |
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Re: ARP head studs
You would be amazed at how much damage happens when someone thinks they need to torque the head studs to anything higher than 55ft/lbs "to contain high compression heads"
The one that always gets me, mill the head for higher compression and then assemble with two gaskets. Does even more damage.
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01-30-2020, 11:36 PM | #10 |
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Re: ARP head studs
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01-31-2020, 12:51 AM | #11 | |
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Re: ARP head studs
Quote:
I bought a B block with NO cracks once for 10 bucks. It had every head stud either broken off or stripped out of the block. Easy fix for me. No so much for others. I sleeved each hole with a tapered steel plug .750 on the OD. The head had 2 o-ring grooves and the block had one that sat in the middle of the head ones. The stud spot face surfaces in the head were enlarged for bigger thicker washers. The head was installed with a solid copper gasket .030 thick. The studs were made from SAE4340M and heat treated to 40RC. The washers were 1.4 inch dia and .250 thick 4340. The off the shelf hard high nuts were torqued to 100 ft. lb. This FLATHEAD engine never blew a head gasket and it went on to win the top fuel 4 cylinder class at the national championship drags running 97% nitroethane and 3% stuff. It would have been nice to have had one of John's 5 main cranks and girdle back then. |
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01-25-2021, 02:06 AM | #12 |
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Re: ARP head studs
Resurrecting this thread to ask: has anyone actually purchased ARP kit 151-4002? Is it real? I'm curious what their torque instructions were.
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01-25-2021, 08:42 AM | #13 |
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Re: ARP head studs
I agree that torque increases the stress in cylinder block threads, but so to does the stud stiffness. Try a rubber bolt analysis and vary the stud stiffness.
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01-25-2021, 10:01 AM | #14 | |
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Re: ARP head studs
Quote:
Been running ARP studs, washers and acorn nuts for 3 years. I have the B-F Super head and the torque is 60 pounds
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01-25-2021, 10:49 AM | #15 |
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ARP head studs
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01-25-2021, 11:58 AM | #16 |
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Re: ARP head studs
Never mind, I asked ARP and they said:
“I’m sorry we haven't released that kit , it is still being tested with R&D.” So there you go, no official guidance yet and no one has purchased the kit (officially). |
01-25-2021, 12:19 PM | #17 |
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Re: ARP head studs
I doubt that ARP will release a stud set for the Model "A", seriously there are bigger fish to fry. Also it should be noted that there are too many different heads available for the Mod"A", and will require many different set options.
Victor, Red's Headers offers ARP studs, you will probably need to measure and provide the lengths you wish. As for suggested torque, 55 ft/lbs is all that is required. I have heard of people running more with higher compression heads but the physics do not change, over torquing will cause problems. I do believe that Larry Brumfield used 60 ft/lbs, that is not excessive. The benefit is the ARP stud/nut combination will give consistent clamping for the applied torque and will not fatigue/yield like other questionable fasteners. As to my experience with them, I use nothing else. From street applications up to race with 300 HP, in the stock locations. John
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01-25-2021, 01:25 PM | #18 |
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Re: ARP head studs
When I bought ARP studs, I had to buy individual studs. No one I talked to there even knew what a Model A Ford was.
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01-25-2021, 03:53 PM | #19 |
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Re: ARP head studs
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01-25-2021, 04:49 PM | #20 |
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Re: ARP head studs
Full disclosure: An ARP employee did some work on several of my cars during vacations in Durango and created a Model A kit that was shipped to me.
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01-26-2021, 11:00 AM | #21 |
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Re: ARP head studs
So if you don't mind me asking, what are we gaining by using ARP studs on a Model-A engine?
I guess my view is with specifically made Model-A/B Grade 8 studs being under $40 (-which includes the hardened nuts), the 7/16-14 threads cut into the cast iron cylinder case are by far the weakest link in the entire scenario. Maybe someone needs to post a pull-out value of a 7/16-14 thread in cast iron, -and then compare those numbers to Grade 5 to Grade 8 (8740) commercially available studs, -vs. the ARP 8740 Moly fastener. FWIW, if someone is going to measure the pull-out strength, the print calls for the threaded hole to be 3/4" deep and to be threaded 7/16-14 USS tap with .392 +/- pitch diameter. |
01-26-2021, 11:55 AM | #22 |
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Re: ARP head studs
I can't speak for others, but my interest in ARP is specifically about their claim that with their studs and lube (Ultra-Torque), you can substantially cut preload scatter.
As you and I discussed yesterday, a Model A head doesn't require preload anywhere near the yield point of a Grade 8 stud. So when we're torquing to 55 (or 60 or 65), we're doing so for a number of reasons that aren't strictly about engineering: - to compensate for a non-flat deck - because that's (roughly) how they did it at the factory - out of the proverbial abundance of caution The problem is that there's only so many times you can put 8,000 or 10,000 lbs of clamp load on the block before the threads start to pull out. The further problem is that the preload you're applying isn't consistent: - if you torque 10 studs to 55 lbs, even with oil on the nut threads, the actual preload can vary by +/- 8% - if someone is re-using fasteners, the preload will go either up or down consistently* every time you reuse that stud/nut * - (whether it goes up or down seems to depend on the nature of the operation - if the fine threads are being progressively distorted, clamp load goes down; if they're being merely burnished, clamp load goes up) Either scenario creates a risk that some of your block threads will experience a clamp load much higher than you intended, which degrades them and increases your risk of head gasket failure. ARP's claim is that, with their studs and lube, you can hit exactly the same preload every time, both across multiple fasteners and using the same fastener multiple times. If that turned out to be true, it might be really good to use ARP for Model A blocks because you would have confidence that the preload you were applying was consistently within the block's ability to take without distorting. We talk sometimes about having a responsibility as a caretaker for these cars – it feels to me like, if a vendor is proposing that their product reduces the risk of accidentally over-torquing the block, that's something we should at least take a look at as part of the mission to preserve these blocks. Last edited by alexiskai; 01-26-2021 at 12:26 PM. |
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01-26-2021, 12:49 PM | #23 |
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Re: ARP head studs
As a side note, I did some back-of-the-envelope math on torque. This is purely speculation, not advice and certainly not an expert opinion.
Maximum compression ratio likely to be used on hobbyist Model A head: 7:1 Peak combustion pressure, rule of thumb, 100x CR: 100 x 7 = 700 psi per cylinder Maximum cylinder bore ~4 inches across, so area = 4(pi) sq. in. 700 psi x 4(pi) sq. in. = 2800(pi) lbs peak lift force on the head Rule of thumb, you need clamp load of 3x peak lift force to prevent head lift-off, so 3x 2800(pi) = 8400(pi) or about 26,400 lbs of clamp force Each cylinder is surrounded by five head studs, so the clamp force per stud needs to be 26,400 / 5 = ~5300 lbs. If that math is right (and I have no idea whether it is right), the minimum required torque on a flat head, with a flat deck and good lubrication, could be as low as 30 ft-lbs. I mention it not to argue that we should be torquing to 30 ft-lbs, but rather that it might be the case that over-torquing studs is the rule rather than the exception. We don't know! I wouldn't be surprised if the factory put a higher clamp load on the studs than was strictly needed. But if you keep doing that for 90 years, what does that do to the block? I think it's worth investigating. |
01-26-2021, 01:59 PM | #24 |
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Re: ARP head studs
Brent has asked the right question, for a stock motor no gain, in my opinion.
As for the others who have the tendency to increase power output it is optional. If you look at the grade 8 specifications, for torque, it is usually limited to about 50 or 60 ft/lbs. (7/16" fastener) I have had grade 8 bolts yield at 55 ft/lbs. Once this happens, the bolt is junk. Broken off studs in a block? I hate having to dig them out, most are machined and the threads saved in the block, not always. Trust me, I get them when others have tried and given up. Why did the stud break off in the first place? In critical assemblies, better fasteners are necessary. As for the strength of threads in the block, on performance motors, I test every one. I have a couple ARP studs just for this purpose, consistency makes a difference. John
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01-26-2021, 02:09 PM | #25 | |
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Re: ARP head studs
Quote:
This is why I'm looking at preload scatter. If the test protocol has high scatter, the test might lead to both low preload values (too low to simulate the real force on the engine block) and high preload values (so high as to damage the block). Last edited by alexiskai; 01-26-2021 at 02:22 PM. |
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01-26-2021, 06:58 PM | #26 | |
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Re: ARP head studs
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Quote:
The issues of deck rigidity, head rigidity and the gasket compression all come into play. The worst situation is when two head compressive type gaskets are used, this is just inviting trouble. John
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01-27-2021, 10:54 AM | #27 | |
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Re: ARP head studs
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01-27-2021, 01:00 PM | #28 |
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Re: ARP head studs
I use the ARP studs in my engine. The thing I like is the allen head socket in the top end. It's a lot easier to pull the head of you remove the nuts and then unscrew the studs. With this setup, I can remove and install the head without removing the fan and water pump.
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