F20 rod shim orientation

[dep]

How is the shim stack supposed to go on the F20/30? Mine are all different so I cant tell. Do the 2 thick shims go top and bottom with the thin ones in between? Also the thick shims have a rige on on side. Does this ridge face in or out and against the bearing?

 

[Nebraska Kirk]

Yes, the two thick shims go on the outside with the thin ones sandwiched in between and the ridge facing out so it goes against the bearing shell.

 

[dep]

Ahhh thank you Kirk!

 

[Nebraska Kirk]

Are you familiar with the procedure for adjusting the rod caps via those .002" shims?

 

[F-Dean]

What clearance do you guys use on a F-20? I do not work mine very hard, so I go with 0.004 and/or 0.005 using Pasti-Guage.

 

[Nebraska Kirk]

(quoted from post at 16:44:19 01/17/16) What clearance do you guys use on a F-20? I do not work mine very hard, so I go with 0.004 and/or 0.005 using Pasti-Guage.

I don't even use plastigauge.
I find that the technique prescribed by the service manual works the best. It involves trial and error until you find that with X amount of shims on each side and the rod bolts tightened, the bearing is tight and then by adding one more shim to each side it then rotates freely. I always fit and shim each bearing to the crankshaft before I even install any of the pistons & rods and make sure I rotate the crankshaft one full turn to make sure the bearing has adequate clearance all way around. If it gets tight part way around, you know you need to add another shim to each side of the rod.

 

[Nebraska Kirk]

This procedure insures the best fit possible, especially when dealing with out of round journals. And some out-of-round will not hurt a bit, these old engines are very forgiving, I have a 22-36 whose worst rod journal measured .005-.007 out of round, I just tightened up the bearings as much as possible while still giving it enough clearance to rotate freely and it runs great and does not knock.

 

[Brian Schmidt]

Here is how we did it last summer on our '38 F-20. Adjusting the shims on the "bench" made it pretty easy.