Main Bearing Bolts, Nuts, Washers

T

tomii

Junior Member
So, after a long hiatus, I'm finally getting back to working on my truck.


I've had the engine machined - old babbits removed (they were shot right square in the butt), and replaced with inserts. The machine shop gave me a set of grade 8 (5?) replacement bolts - anodized, with flat washers, and tall (taller than the castle nuts that were on it originally).


I assembled the crank & mains with the new bolts, but I don't like that the bolts aren't staked somehow. I am missing one of my original crenelated nuts from the mains, so I went off and ordered a new set of nuts from Brattons.


Got the new nuts in - thought I would reuse the flat washers from the machine shop along with the original bolts & the new nuts.


Problems, though - I did not take good enough pictures during my teardown. The tow rear main nuts (with washers under them) do not appear to go far enough down (it seems) to allow the holes to align for cotter pins.


So, here's the questions:
a) Which (original) nuts should have washer under them? All? Not the ones inside the crankcase?


b) Thoughts on using the machinists' nuts & bolts?


c) Would Lock-tite work as the staking compound - assuming I use the machinists' hardware? (I don't like relying on torque alone, especially where there's vibrations - but I've never used Lock-tite under torque)


Thanks in advance.
 
originally just bolt with square head, castle nut, cotter pin ---on one corner of square head is a little bump to indicate cotter hole
 
I never use castellated nuts on mains or rods, they only have about 3 full threads that they pull against, just grade 8 or ARP nuts, no lock-tite or anything else either. I race B engines, never had a problem.
 
Kurt in NJ said:
originally just bolt with square head, castle nut, cotter pin ---on one corner of square head is a little bump to indicate cotter hole
Click to expand...

Just a note on what I do to help with cotter pins is I put a line on the end of the bolts with a white paint pen lined up with the cotter pin holes. Wipes off with acetone afterwards.
 
Also be aware that a pressure engine WILL pump oil up the bolts from the mains, so they need to be sealed where they exit the block.
 
I have read of folks who put seals / copper washers on the main bearing bolts. In any combination of hardware in a high strength application there should not be a piece with a lower compressive yield strength because it will yield under load and loosen the joint.
 
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Phosphate coated grade 8 tall nuts,metric hard washers filed to slide on main bolts,three bond sealant on the washer,blue loctite on the assembly.Cotter pins are effective to eliminate disassembly,but fail at holding torque. Anaerobic sealants (loctite) retains the assembly at the torque applied to it.
 
I had used long Caterpillar nuts for quite awhile, then could no longer find them at the local Cat dealer, so machined Model A lug nuts flat, sillyconed the bolt threads a little to prevent leaks, and assembled everything. So now I have good thread contact, good quality nuts, and they look cool too!
 
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