This was something I looked into with a 2 bolt main block (see above post about the block and rotating assembly), and I've been "told" it HAS to be line bored after studs are installed, but I can't give you the specific reasoning for it. I too thought what's the real difference between bolts and studs. Maybe someone else has THE actual answer. I am Butch/56sedandelivery.
Just because a hole needs a Heli-Coil why should that require main studs and their added expense? Put the main bolt back in the hole, unless of course it’s stretched or has damaged threads. Heli-Coil threads are strong when properly installed, we put a 9/16-18 H-C in a Brad Anderson billet hemi block, it was for a long head stud that tied into the block real deep. That stud took 160 ft. lbs. and even at that torque in an aluminum block never gave a problem.
Studs on mains and heads have fine threads for the nuts and the torque is applied differently. Obviously, torquing is the same but the clamping load (engineering term, not mine) is superior and could cause bore distortion. Studs first, check the bore diameters and the main bore alignment and is necessary align bore.
OK, so I Googled the "reasoning", and there are a lot of un-professional opinions both pro and con regarding main studs. However, professionally, due to increased clamping forces, and the resulting stresses/distortion placed on the block/caps, line HONING is "required". Line BORING is not the proper term here. Ya'll can also look it up for confirmation if you care too. I suppose using studs would be in a more high dollar engine, and closer tolerances adhered too for that reason. There is also a specific way of installing studs; they're not just loc-tighted, and screwed in; gradual torque increments, similar to head bolts, are used. As far as the issue the OP is having, and wanting to use a helicoil, it too has to be installed in a specific fashion; it's not just hand drill-out, tap, install. The helicoil has to be completely concentric and centered properly, otherwise, distortion of the cap and/or block can/will occur. With a street purposed engine, it may not be that important, but then again.................................... I am Butch/56sedandelivery.
Thank you Butch/56 sedan delivery for the offer of the 283 - that is a very decent and generous offer .But I have a line on one locally that I hope will pan out.
^^^Same deal on my .060 over 283 and balanced rotating assembly with forged/popup .125 pistons. Come get it, it's yours, whoever wants it. I am Butch/56sedandelivery.
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