C90 rods ?

Can someone describe why the connecting rods are numbered and
why it is important to have them in proper order & direction.
When I lay them on the bench they look the same and the
oil hole on the rod caps all seam to be drilled at the same angle.
I just want to understand more on how this oil hole works ?

Thanks, Jon

I can help a little: Factory balances them in pairs to the nearest half-pound or so. Often they are enough different that you can't split them up. We use Performance Aero at Brackett Field to finish the balance. Send them the rods, pins, bearings, pistons, and crank. Shipping is most of the expense.

Oil holes are to lubricate and cool the pistons. Not necessary in A65 and 75, but required on 85 and up. Make sure bearings line up, so oil can get out.

A75's and up got them oil holes, Oil press shoots a stream of oil from the rod cap across the case to the bottom of the opposing piston. Helps to cool the piston down. The overhaul shop numbers the rods for weight so put them in their proper places. Make sure the oil squirter hole points the right way when you install them so that the oil hits the opposing piston and not the inner case wall. C90 and 0-200 rods have the bottom of the rod caps machined flat so the piston skirt of the opposing cylinder will just clear it at BDC, they have a slightly longer stroke than the smaller cont. engines.

Is this engine goin in a certified plane?

Jason
N43643

Jason, No it is not, but I am using all certified parts. The engine had only
100 hrs on it when I found microscopic steel particles with an oil
test. I removed the engine to find the bottom of each cylinder
was wearing on one side. This is the second time this has happened
in 300hrs. When I split the engine I did not look to see if
the oil holes were properly installed. I have had the engine both
times assembled by a IA.
Thanks Jon

If memory serves me correctly the OH manual says to put the rods on their corresponding journals extended to their appropriate position with the numbers stamped on the rods/caps facing down. This is from memory and I would look it up. I can't remember all this stuff but I rebuild several engines a year and follow the OH manual step by step so I don't forget something like this.

give sacramento sky ranch a call about the your wear issues.

http://www.sacskyranch.com/

call me when you have a minute and I can tell you about some experiances with a friends "built" c90 and wear issues.

Jason
206-930-2332

Jon: Check to see if the rod squirt holes actually point where the are suppose to. I have seen them improperly drilled. In this case the rod has to be rotated with the number the opposite way. As far as the wear you described, look for how level the cylinder decks are and make sure the rods are straight and the rod bearing and wrist pin bushings are parallel to each other.
Ron

Jon , if you want to correct this wear problem you might want to cosider more inverted flight. Thanks for the questionable eletrical work. Did you say my wife should be standing in shallow water when operating the float plane dolly?