ARP studs stretch?

[wild_maxx]

I was planning on re-using my ARP main studs but now i'm not so sure. I used them on my built e-t motor for around 1500 miles. I pulled them out of the motor and did some measuring with a micrometer. Some of the studs are longer than others. I'm not talking about the 3 longer studs but the 5 shorter ones.

Of the 5 shorter studs there was about a .010" difference in the size of them. I don't have my sheet right now.. but there was a difference in the length of the studs.

After doing some reading on ARP tech pages I think the difference may be due to me not stretching them properly before doing my final torque on all the mains. I just installed them by hand using ARP lube then put the gurdle on and torqued 40. then 70 lbs. Is it possible that some of the studs stretched and others did not fully stretch?

Is it safe to re-use the studs? My turbo240 rods are also equiped with arp bolts and have been torqued already.. so can I re-use them all?

http://www.arp-bolts.com/Tech/TechTorqu ... stall.html

[rotorimp]

Do not reuse them you waaayyy over torqued them. Where did you come up with 70 for the mains--you nearly doubled the arp spec. Nissan spec is 38 ft/lbs----and that is on stock fasteners!!!!!! When your dealing with ARP and using the moly lube then that torque is much less due to the reduced friction.

This is directly form ARP!1. The friction factor changes from one application to the next. That is, the friction is at its highest value when the fastener is first tightened. Each additional time the fastener is torqued and loosened, this value gets smaller. Eventually the friction levels out and becomes constant for all following repetitions. Therefore, new fasteners should be tightened and loosened through several cycles before applying final torque. The number of times depends on the lubricant. For all situations where ARP lubricants are used, five cycles are required before final torquing.

2. The lubricant used is the main factor in determining friction, and therefore, the torque for a particular installation. Motor oil is a commonly used lubricant because of it’s ready availability. If less friction is desired in order to install the fasteners with less torque, special low friction lubricants are available. With special lubes, the required torque can be reduced as much as 20 to 30 percent. It is important to keep in mind that the reverse is also true. If the torque value has been specified for a particular fastener on the basis of low friction lube, installing the fastener with motor oil will result in insufficient preload; the torque has to be increased to compensate for the extra friction caused by the motor oil.

[yessir240]

man GREAT explanation. A friend had a fully built 2.4 dsm awd with a gt40r pushing near 500 whp. He spiked 40psi on the dyno and the head prob floated when he did this, then him and another guy re-torqued the head bolts to 110 and then later that night they blew the hg. so yea they do stretch.

[wild_maxx]

I screwed up my first post... I torqued the HEAD studs to 70 ft lbs not the mains. I believe I torqued the main to factory spec. I think i'm just gonna replace them anyway... rather spend the 115 bux now than rebuild it again...