Wedge Using TR7 Main Bearing Studs on a TR6: how to note

[atgordon]

This was a topic that started on the 6-Pack list, and in the hope that what I have learned might benefit others on the Britcar forum, I am posting the info here as well.

Put briefly, I was interested in using studs for retaining the main bearings in the rebuild of my TR6 engine. After a lot of discussion on the 6Pack list, it appeared that others had managed to use the ARP main bearing stud kit designed for the TR& on the TR6. But after a lot of asking, I was unable to find out what they had done.

I was intrigued since the front main bearing is covered by the aluminium sealing bar, and they're ain't a lot of room to fit studs, so I went ahead and did all the measurements and calculations, and low and behold, it is a very simple process, and I have written it up in the hope that others will find it useful.

The PDF can be downloaded from here TR7 Studs TR6

 

[tdskip]

Thanks.

What is the advantage of doing this?

 

[DNK]

The reason you didn't get a response is
You didn't know the Secret Handshake

 

[DNK]

Thanks.

What is the advantage of doing this?

Studs are stronger than bolts,Tom

Clarification
The clamping power is greater

 

[vettedog72]

With out being way too technical, how/why are studs stronger than bolts?

 

[atgordon]

With out being way too technical, how/why are studs stronger than bolts?

I did put a couple of references in the article that gave a further information on the topic. Here is a very brief summary (it refers to cylinder head bolts, but the same concepts apply to main bearings too):

<span style="font-style: italic">"During engine assembly or maintenance, a bolt must be installed by torqueing it into place. Due to the head bolt’s design, it has to be rotated into its slot in order to engage the threads and secure it into place. This process creates both twisting force and a vertical clamping force, which means that when the cylinders within the engine’s combustion chamber begin accumulating load, the bolt will both stretch and twist. Because the bolt has to react to two different forces simultaneously, its capacity to secure the head is slightly reduced and it forms a less reliable seal in high-powered engines.

By contrast, a head stud can be tightened into place without any direct clamping force applied through the tightening. A stud can be threaded into a slot up to “finger tightness,” or the degree to which it would be tightened by hand. Afterward, the cylinder head is installed and a nut is torqued into place against the stud. The nut torque provides the clamping force, rather than the torque of the fastener itself, and the rotational force is avoided entirely. Because the stud is torqued from a relaxed state, the pressure from the nut will make it stretch only along the vertical axis without a concurrent twisting load. The result is a more evenly distributed and accurate torque load compared to that of the head bolt. This ultimately translates into higher reliability and a lower chance of head gasket failure."</span> (from https://www.thomasnet.com/articles/hardware/head-stud-bolts).

 

[Darrell_Walker]

That would also imply that regular bolt/nut combinations should be tightened by turning the nut, rather than the bolt, if possible. Of course, most fasteners don't have to deal with the same loads a head, rod and main bearing fasteners do.

 

[atgordon]

Agreed! It is much better practice to tighten a nut (particularly when tightening to a torque setting). But we then get into the whole issue of wet or dry torque tightening ... (if a fastener is lubricated, the required torque to tension it is greatly reduced!).

Incidentally, the reason studs are not more commonplace is largely to do with the ease of automated assembly of bolted components. Plus, separating of multiple stud-fastened items (such as the cylinder head on a TR6) can be a royal PIA.