Piston orientation

F

Flying Ant

Filing Flight Plan
Joined
Feb 3, 2012
Messages
10
Display Name
Display name:
Flying Ant
I'm installing my cylinders on the engine and the overhaul manual says to

"Assemble piston on connecting rod with piston number, which is stamped on bottom of piston head, toward the front of the engine."

I have 10:1 compression ratio LW11487 pistons from an HIO 360 D1A so they have the indents on the piston crown for the valves, so I guess it matters which way they go. I can't for the life of me find the piston number anywhere on it. The only number I can find is the part number and its in the middle inside the piston (underneath crown) so I'm not sure which way to orient it.
 
If you have fly cuts in the piston that only install one way to the valves the answer becomes obvious.
 
Henning said:
If you have fly cuts in the piston that only install one way to the valves the answer becomes obvious.
Click to expand...

+1...

Additional hint.... The intake valves are bigger then the exhaust valves.;)
 
Flying Ant said:
I'm installing my cylinders on the engine and the overhaul manual says to

"Assemble piston on connecting rod with piston number, which is stamped on bottom of piston head, toward the front of the engine."

I have 10:1 compression ratio LW11487 pistons from an HIO 360 D1A so they have the indents on the piston crown for the valves, so I guess it matters which way they go. I can't for the life of me find the piston number anywhere on it. The only number I can find is the part number and its in the middle inside the piston (underneath crown) so I'm not sure which way to orient it.
Click to expand...
Have you looked inside the piston skirts or in the recessed area by the wrist pin caps?
 
What makes you think that he's not working on an experimental?
 
No, he just has to look at the fly cut marks and figure out which way they go since they aren't marked as indicated in the manual. It's just an engine, they aren't complicated.
 
If there are fly cuts, quite often there aren't however as this is a 10:1 they may well exist.
 
Flying Ant said:
I'm sorry I asked.
Click to expand...

A common reaction on this and other online sites. I see you're a pretty new member. People can be unbelievably cruel, sometimes casually, without thinking about it, but sometimes out of arrogance or even meanness. I suppose I'm as bad, myself.

Well, I've never rebuilt an aircraft engine, but I can tell you that on my tractor engine, if the rods went in wrong the engine would not turn over completely. You can look at the rods, see how they differ, put one in each way and see which one has interference. That's the tractor method. Plus, I could get on Yesterday's Tractors and get an answer almost certainly without making me feel like an idiot.

For airplanes, I don't know.
 
No difference in aircraft and tractor engines except a water jacket and pump, and not always those either.
 
Are these Lycoming pistons or after market?

The overhaul manual will only address Lycoming materials.
 
I'll post this just in-case someone else happens across this thread with the same question.

I took a piston into the overhaul shop I used and they agreed that the instruction was not good as piston numbers are no longer stamped on pistons.

The good news is that the valve pockets are symmetrical and out of habit they insert them with the part number facing up the right way, but it doesn't really matter. One of these days I'll ask Lycoming directly.
 
Piston orientation in autos can be critical. In some turbocharged engines, the pin is offset so that a straighter push is obtained on the power stroke. The offset isn't readily visible. Now I'm wondering if any aircraft engines have offset piston pins.

Dan
 
Normally IF it matters, the marking will be less than discrete, like big notches and one way pop tops in a wedge head.
 
A lot of aircraft maintenence documentation is really poor error filled junk that will never be corrected. It makes a lot of steady work for someone like myself employed as an engineer at an airline. FAA tells you to do it by the book and you simply can't.
 
You must log in or register to reply here.
Back
Top