Subject	Stock head bolt tensile tests >>>
Posted by	LitlElvis on April 05, 2010 at 5:19 PM
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Message	I tensile tested two stock VG30DETT head bolts today to see just how strong they are. They came up at 186ksi with a yield of ~165ksi. As you can see below, they both broke in the same place in roughly the same manner. The point of fracture is due to the threads reducing the cross-section at the root of the thread. I was hoping they would break somewhere in the middle of the shank for a good elongation and reduction of area measurement, but so be it. FYI - this does not mean they are junk, it's just a measuremnt in which someone can use to compare to other alternatives out there, that is all it is good for.
Follow Ups	Stock head bolt tensile tests >>> - LitlElvis 17:19:23 04/05/10 have you tested the replace ARP studs for reference? - Carlos Ramirez 17:37:15 04/05/10 ARP lists their standard 8740 studs to be 200ksi - LitlElvis 17:47:04 04/05/10 Interesting... - Gold300zx 17:38:36 04/05/10 I'm curious, was the breakpoint at the nut, or does it have - zellamay 17:53:55 04/05/10 it's more to do with the start of the threads - LitlElvis 21:37:58 04/05/10 To clarify, if the threaded portion was longer, and the - zellamay 21:59:16 04/05/10 it will break where the threads start to form on the shank - LitlElvis 22:05:54 04/05/10 Thanks, you have been very informative. (n/m) - zellamay 23:14:59 04/05/10 So the bolts dont really stretch? Just break.... (n/m) - ZXoltan 18:37:31 04/05/10 Yes they stretch - Brad(RI) 18:53:41 04/05/10 The threads are rolled. Like you, I hoped this would - LitlElvis 07:54:18 04/06/10 Out of curiosity... - Obeeone 19:13:36 04/05/10 Re: Out of curiosity... - Brett@AwesomeZ 19:31:20 04/05/10 Re: Re: Out of curiosity... - Brett@AwesomeZ 19:32:30 04/05/10 The graphs and some math tell the tale that you want to see - LitlElvis 22:03:39 04/05/10 This is not about outright failure of head bolts - LitlElvis 21:50:30 04/05/10 Never seen one issue with the factory head bolts yet (n/m) - Seb@Specialty-Z 22:36:43 04/05/10 Seb, what's the highest HP you have run with stock bolts? (n/m) - ZXoltan 07:45:11 04/06/10 a little over 1000 BHP (n/m) - Seb@Specialty-Z 10:12:31 04/06/10 Do you guys recommend the stock head gaskets or MLS styles? - KongZTT GT28RS MD 01:48:13 04/07/10 Exactly, it's not about breaking bolts - Brett@AwesomeZ 00:44:29 04/06/10 typically, fasteners are preloaded to 75% of yield strength - LitlElvis 07:16:53 04/06/10 I thought stock head bolts fell into this stretch category. (n/m) - Antihero 08:36:50 04/06/10 All fasteners stretch when preloaded, the key is to not - LitlElvis 11:56:01 04/06/10 the new ARP L19 hardware... - KongZTT GT28RS MD 01:54:07 04/07/10 You have an instron in your shop? Impressive! (n/m) - Scotts94z32 11:44:26 04/06/10 It's not mine, I just get access to it :-) (n/m) - LitlElvis 12:07:25 04/06/10 What adjustment factor do you apply to the steel>> - ZUL8TR 14:37:31 04/06/10 This is perfect.. I have been thinking of pulling - KongZTT GT28RS MD 01:41:27 04/07/10 err.. L19 (n/m) - KongZTT GT28RS MD 01:46:06 04/07/10
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