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Modified Main Tunnel and Larger Size Fasteners (NISSAN RB)

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Hello HPA,

I have recently received my Block from the machinig where it was fitted with the Billet Main Caps and Girdle. Also, threaded holes of the main studs were enlraged from M10 to M12 size.

When I tried to perform first assembly of the main tunnel - I noticed that new ARP M12 studs I used for this setup (RB26 HSK) differ from genuine RB26 ARP M10 Main Studs (MSK) not only by the thread size.

Main studs from the ARP kit have have some kind of "elongation" after the thread which comes to the block (sorry for poor English, hope you will understand what I mean).

The machinist who performed main caps installation gave me 14 "shims", which were placed into every threaded hole before he torqued down the main caps.

Is the better option for me to find M12x1.5 ARP studs which have this "elongation" after the threads or it is common practice to use RB26 studs on the mains? What studs RB builders are usually use for the billet main tunnel on the stock Block?

Thanks a lot.

If I understand you correctly then the elongation you're referring to is a small extension on the end of the stud after the threads. This is designed to bottom in the stud hole against the block and ensures the threads are stressed equally. This is quite normal and not a problem. I'm not sure what you're referring to when you mention your machinist used shims? An alternative I've used is to drop a small ball bearing down the stud holes to achieve the same aim - The stud bottoms on the ball bearing rather than in the bottom of the stud hole.


Once again my apologies for the poor language and thanks for the advice. I think I am going to use ball bearings from the friction package of R35 Transmission ETS unit. The size seems to be very close.