Centre Web Bolt Tension

Arti51 · Post by **Arti51** » Fri May 02, 2008 11:54 am

To those with the knowledge.
I am a bit confused at present on what is the correct lb ft tension for the centre web main bearing retainers.
By my past experience a 7/16 W grade 5 stud would require 42 - 48 lb ft as a standard tension.
In the two publications I have on Twin engine rebuilds one states(F.E Neill) install crank and tension cap retainers to 11 lb ft.
In the other (Ernie Merryweather) instal crank and tension retainers to 20 lb ft.
Please enlighten me on what would be the correct tension here. Also why is the tension so low for a large retainer.
Cheers
Arti51

Biscuit · Post by **Biscuit** » Fri May 02, 2008 12:36 pm

Don't really know the answer, except it is not Whitworth it is BSF and there were two sizes of this stud in 1951, 7/16" and 3/8" which may explain the differing torques.

Eric · Post by **Eric** » Fri May 02, 2008 5:46 pm

The main reason the torque settings are lower than you may have been used to in the past is that the threads are in Aluminium not steel or cast iron and are as Alan says BSF not Whitworth, so for this sort of application they are a rather fine thread that could be stripped out if overtightened.

CR · Post by CR » Fri May 02, 2008 6:56 pm

ALWAYS use new locking nuts and tighten to 20 ft.Ibs. Always check that the crankshaft is free to turn after centre web assembly.

Just in case you were going to ask, ALWAYS use new self locking nuts on the conrods too and tighten to 22 ft.Ibs.

I always assemble with colloidal graphite on the shell faces, and the test is for the rods to slowly fall from vertical under their own weight.

As previously stated, the threads are BSF.