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02-17-2022, 05:56 PM | #26 |
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The M11 OD is about .4331", whereas the 1/2"-13 tap drill is .4219". Yeah...Caroll Smith would not like this.
I wish I had paid more attention to this when deciding on my closed deck combo...I was being lazy in not wanting to machine head for new dowels, so I didn't go M14. Doh. I think the "saving graces" might be the length of threads (much more than two diameters? I might check my block) and the fact this is a stud vs. bolt, so no turning/friction/wear effects.
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02-18-2022, 09:43 AM | #27 | |
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03-02-2022, 05:31 PM | #28 |
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i've often wondered how much the tension changes on the head studs when these motors come up to temp
some of the all aluminum or magnesium air cooled car and bike hot rod and race motors that i have played with ABSOLUTELY REQUIRED that they be brought up to temp before putting them under load to keep them from pushing head or base gaskets out (or whacking a piston into the head) fuel for the discussions fire : imo , unless its a balls out high hp build strung way out on crack at the very outer limits , the 1/2" studs would be more than fine , not a 800 up build , one thats understressed and with a spot on tune i get it 10000% , but do you see where i'm coming from ? i think they have their place hi clint |
03-02-2022, 05:54 PM | #29 | |
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I just got off the phone with Micah. We're seeing some rather odd numbers in regard to ARP2000 vs. ARP 625, that honestly don't make any sense. I'm going to have to talk to ARP to get their input on it if they are willing to do so. One of the factors that I brought up in the call is the heat, but Micah is of the opinion that the heat in that location, with the studs being isolated from the cylinders due to the cooling jackets is so insignificant that it would not play a factor regarding clamping force. |
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03-02-2022, 10:42 PM | #30 | |
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I think there will be a increase in clamping force when going from room temperature to operating temperature. This will be proportional the difference in thermal expansion coefficient and temperature change. Here is quick calc for an M11 stud I did while waiting for water to boil while making dinner tonight.... L = .150 (active length of stud/clamped length in meters) d = .0105 ( diameter of stud in meters) T0 = 20 (initial temp. in deg. C) T1 = 100 (operating temp. in deg. C) (guestimate...would not be surprised if higher) a_steel = 10.5E-6 (CTE of steel in m/m/C) a_aluminum = 22E-6 (CTE of steel in m/m/C) (very reasonable for the block alloy methinks) a_d = 9.5E-6 (difference in CTEs) Est = 206E9 (elastic modulus of steel in Pa) Eal = 70E9 (elastic modulus of steel in Pa) Ast = .25*pi*d^2 = 8.6590e-05 (area of stud in m^2) Abl = .25*pi*(10*d)^2 (effective area of block in m^s) kst = Ast*Est/L = 1.1892e+07 (stiffness of stud in N/m) kbl = Abl*Ebl/L = 4.0409e+08 (stiffness of active block area in Nm) keq = 1.1892e+07 (equivalent stiffness of stud and block in series) x = L*a_steel*a_d = .000150 (thermally induced length change in meters) x = .0059" (in barbaric units) F = keq*x*a_d = 1.3169e+04 (increase in clamping load in N) F = 2953 lb If you do this neglecting the block stiffness, the result is good approximation too because block is >> stiffer than stud, as a good joint design should be. All of that said, there will be significant increase in clamping, probably on the order of 19% (or more) of initial clamping load (?). The total load on the joint needs to take into account: initial tensioning + cylinder pressure + thermal load. I think for M11, we are far away from loads which will cause thread failure in hole. There are cases where these things are not accounted for correctly and bolted joints fail in operating conditions. As for the question of "what temperature does the stud see during operation?" we can think about this two ways. First, the stud reaches some equilibrium temperature, and that temperature is probably pretty close to the block temperature given decent conduction path. I suspect my 100 C (212 F) is pretty reasonable guess. Then you would get what I show above. if we assume the stud remains much closer to room temperature, then you have much greater loading...you are then closer the the CTE of aluminum for estimating the thermal expansion. That would increase the loading, not reduce it. If stud were to remain at room temp, then you would roughly double the clamping force increase. So...we should hope that they actually do get close in temperature to the block. I can't see any reason why they would not be at or above coolant temperature. |
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03-03-2022, 06:50 AM | #31 | |
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Clamping force absolutely increases with temp, for ALL the engine's fasteners. If ICEs lived a thermally harmonious life, it would pretty much eliminate ever having gasket leaks of any kind. On this topic, the temp issue is even less clear than cpreissner's mathematical example. Normal operating conditions have a range based on conditions. An engine is going to operate much cooler cruising down the highway at 70 on a 50° day vs hot laps on a 100° day. Not even taking into consideration that the track car is likely making more power than the street car. Even if they were both the same, that operational temperature window, will be different. To add even more to the equations, there's likely a difference in stud temperatures of one located near the outside surface of the block and next to an intake port, vs. centrally located and right next to an exhaust port. Even if the exact numbers are no known, it's just math to figure out the theoretical ranges in clamping force. Heck, if anyone is currently out there building a block, throw a tell-tale temp sticker on each stud so we can all know what the temps are. Then the math shifts from theoretical to more practical. |
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03-03-2022, 10:21 AM | #32 |
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I'm not planning on going any higher then 550whp, Like Mike said the 1/2 studs should be fine. But this is the time to change my mine if there is science backing it. I already got the heads taped to 1/2 but not the block.
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03-03-2022, 03:29 PM | #33 |
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Paul , remember, make plan , stick to plan
You’re fine Stay on target |
03-03-2022, 04:13 PM | #34 | |
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I have been thinking of SOME way to make a test rig where I can thermally load a stud and note the affect on clamp. Best I can come up with so far is a frame with my load cell at the top, a block at the bottom, and leave the middle of the stud exposed. Around that do an induction heater that I can vary current on, and put some kind of temp probe on the stud. As for what temp I would obviously look at coolant temp, BUT this raises the question of localized temp at the studs. Would it be higher or lower or what? That part is going to require more thinking. |
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03-03-2022, 06:32 PM | #35 | |
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03-04-2022, 03:26 PM | #36 |
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WAit!
Me too ! You have my email I’m wondering if what you’re seeing is what I have felt and seen on my torque wrench |
03-07-2022, 10:03 AM | #37 |
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03-15-2022, 04:55 PM | #38 | |
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Edit: I should also state that I do not prefer the 14mm due to the material removed from around the mains. It increases distortion seen. Last edited by Homemade WRX; 03-20-2022 at 09:13 AM. |
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03-18-2022, 02:35 PM | #39 |
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Small update. Just got a call from ARP. The data I sent them matches what they have seen from their end. They have some new stuff they want me to check out on my end and see if we match up again.
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06-18-2022, 12:12 PM | #40 |
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waiting for more here ........
and on the 1/2" thing , two words , rolled threads |
06-18-2022, 12:13 PM | #41 |
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waiting for more here ........
and on the 1/2" thing , two words , rolled threads |
06-18-2022, 01:03 PM | #42 |
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Still waiting for samples from ARP. I'll email them again.
Still waiting on other samples. Mike - all the studs should have rolled threads for this. Even the most basic and boring of studs for this application. |
06-18-2022, 02:03 PM | #43 |
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i meant the holes tapped in the block for the oversize studs should be rolled rather than cut with a normal fluted tap
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06-21-2022, 12:47 PM | #44 |
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07-12-2022, 05:24 PM | #45 |
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Internally rolled threads are great, and the norm at the day job. Not so easy to find a competent place to do it.
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07-15-2022, 02:27 PM | #46 |
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P2Pracing does rolled threads on all bigger head stud builds
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07-16-2022, 01:52 PM | #47 | |
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Hi Homemade WRX i was thinking of going 14mm Headstud but now I dont want to any more because of the main bearing Tunnel being out like you said....how much have you seen them being out by ? i dont trust any machine shop here where i live to Line bore the mains..... I prefer a reamer tool but no one has one down here i live so if the mains are out too much i might have to cancel the Idea of 14mm head stud.... i dont think i can get the main bearings back on target with just miss matching other bearing sizes from other bearing kit sizes like others do. |
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07-19-2022, 12:23 PM | #48 | |
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Where do you live? I may be able to make suggestions on the machine work. |
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07-19-2022, 12:25 PM | #49 |
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Small update. I have some new samples on the way to me. Once they arrive I'll test and see what we get.
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