Author Topic: BBC Main Stud Life?  (Read 1274 times)

Offline Dunc the Funk

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BBC Main Stud Life?
« on: May 16, 2020, 09:18:40 AM »
On a blown methanol 517ci BBC with 4 bolt steel main caps on an iron Gen IV truck block with aluminum rods, probably around 1000hp and operating at 7000-8000 rpm max, what sort of life expectancy would you give the main studs e.g. in terms of rebuilds, seasons, runs?

Offline denverflatheader

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Re: BBC Main Stud Life?
« Reply #1 on: May 16, 2020, 05:07:56 PM »
Reference information courtesy from ARP-bolts.com website, select their "Tech" and then "Installation" page:

The Stretch Factor
It is important to note that in order for a fastener to function properly it must be "stretched" a specific amount. The material's ability to "rebound" like a spring is what provides the clamping force. If you were to simply "finger-tighten" a bolt there would be no preload. However, when you apply torque or rotate a fastener a specific amount and stretch it, you will be applying clamping force. The amount of force or preload you can achieve from any bolt or stud depends on the material being used and its ductility, the heat treat, and the diameter of the fastener. Of course, every fastener has a "yield" point! The yield point or yield strength of a fastener is the point at which the fastener has been overtightened and stretched too much, and will not return to its original manufactured length. As a rule of thumb, if you measure a fastener and it is .0005˝ (or more) longer than its original length it has been compromised and must be replaced.

https://arp-bolts.com/p/technical.php


Dunk the Funk - perhaps the answer to your question is more related to the main stud's "yield" point.  I have used ARP bolts/fasteners and they have excellent products and service.  Alan

Offline dusterdave173

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Re: BBC Main Stud Life?
« Reply #2 on: May 18, 2020, 03:34:13 AM »
I think you can run them until you retire--it is the threads in the block that you should keep an eye on during fresh ups--as long as studs go in block finger tight you will be fine -- If you torque them in--the block can and will crack--That ..is the secret to main studs
This opinion based on 30 years of building
I have always had a fascination with fast cars at the expense of more normal character development

dreracecar

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Re: BBC Main Stud Life?
« Reply #3 on: May 18, 2020, 09:09:25 AM »
Even new parts can fail, but I would say that the "over the counter" stud sets are way over-engineered for the application verses the highy engineered F1 stud assemblies and for the most part, those engines do not get rebuilt after a race anyway.  The only way of knowing what is going on is to catalog each bolt out of the box and measure, with frequent checks to log in the results of the changes after the original stretch/set

Offline Dunc the Funk

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Re: BBC Main Stud Life?
« Reply #4 on: May 19, 2020, 03:19:38 AM »
Thanks for responses. I got my motor second hand and I have no idea on the history of some of the parts. I don't want to harass the guy I bought it off as it looks like he has terminal cancer, he's got enough to worry about. So it's up to my judgement to decide what to renew at the moment.

My machinist commented the studs looked ok but the nuts were not good. I tried some new nuts on the studs but I think the stud threads are past their best as there are tight spots on them. Seeing as we had fretting on the mains, I think now is a good time for a new set of studs (ARP, what else?). I got a tin of ARPs Ultra Torque lube already. Hopefully they will clamp the caps properly and I will feel a bit less anxious as the car goes into stage!

dreracecar

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Re: BBC Main Stud Life?
« Reply #5 on: May 19, 2020, 08:36:41 AM »
Fretting is just part of the deal with a blown engine even with new parts, you dont see it with the big show engines because they dont stay together long enough