ArVeeNiner
Well Known Member
I have an O-320 B2B that I got used. I'm in the process of pulling off cylinders to paint them and have a look see.
At the base of my cylinders are two steel hold down plates each. I have both 1/2" and 3/8" nuts holding the cylinders on. The overhaul manual has you put 4 each 0.010" shims near each of the 3/8" nuts. Supposely these are to provide a gap beneath the hold down plates and the flange on the cylinder barrel. I honestly didn't see how there could possibly be a gap remaining after torquing down the nuts.
So, per the instructions, I put the shims in (feeler gauges), torqued up the large nuts to 25 ft-lbs, removed the shims, torqued the large nuts this time to 50 ft-lbs, and finally torqued the smaller nuts to their final torque of 25 ft-lbs. Sure enough, there isn't a gap under the hold down plates. In fact, the remaining cylinders don't have a gap either. What gives? This engine flew for years on a Pitts with no problem and no gaps.
Can you actually get a gap under this plate? Do I need to worry about it at all?
At the base of my cylinders are two steel hold down plates each. I have both 1/2" and 3/8" nuts holding the cylinders on. The overhaul manual has you put 4 each 0.010" shims near each of the 3/8" nuts. Supposely these are to provide a gap beneath the hold down plates and the flange on the cylinder barrel. I honestly didn't see how there could possibly be a gap remaining after torquing down the nuts.
So, per the instructions, I put the shims in (feeler gauges), torqued up the large nuts to 25 ft-lbs, removed the shims, torqued the large nuts this time to 50 ft-lbs, and finally torqued the smaller nuts to their final torque of 25 ft-lbs. Sure enough, there isn't a gap under the hold down plates. In fact, the remaining cylinders don't have a gap either. What gives? This engine flew for years on a Pitts with no problem and no gaps.
Can you actually get a gap under this plate? Do I need to worry about it at all?
