Ever wondered how well your pistons are balanced?

[rwtalbot]

These pictures are from a set of pistons straight out of my Mattituck / ECI engine. The cylinders are being replaced at 347 hrs TTIS due to the AD. On a whim I decided to throw them on the scales I keep in the hanger. The pistons are as removed, with the rings still on and the piston pins in.

I'm pretty impressed the ECI logo in black paint is still visible on the piston wall. Sure makes you appreciate why reducing RPM results in better fuel efficiency with the inertia in these big pistons.

Cylinder 1 & 2


Cylinder 3 & 4


__________________
Richard Talbot
RV-7A
Sydney, Australia

[Walt]

The plots here also tell the story of internal engine balance, the 2X blade rate corresponds to piston/rod balance.

[bret]

The clean piston skirt shows good ring sealing, correct break in!

[eddieseve]

Very nice Richard, hope mine are doing as well.

[rhill]

What is the +/- of the pistons,rings,wrist pins&caps in grams,I'm going through this now and I'm within two grams,2 even,1 one gram heavy,1 one gram light.
Matatuck had a huge inventory to pick through on there builds.If I need to bring the three down to the lowest one,Where do I remove the weight?Is there any advantage to the heavy weight piston,heavy wall pins over lighter Superior supplied Pistons/pins?
On a 911 engine I would move these heavy units to the rear near the fly wheel and keep opposing weights the same,Can I do that with a Lycoming?
Thanks
Bob

[rwtalbot]

Originally Posted by rhill

What is the +/- of the pistons,rings,wrist pins&caps in grams,I'm going through this now and I'm within two grams,2 even,1 one gram heavy,1 one gram light.

Bob, I can't answer your question completely as I am only doing the cylinders. My new cylinders from ECI came with piston and rings. The pistons and rings were all weighed in the factory and marked on the box, balanced to the gram. If this is anything to go by, how much Mattituck would need to do on an ECI engine is questionable.

There is a lot more to balancing the bottom end than just weighing the components but I am sure it would be a good start.

__________________
Richard Talbot
RV-7A
Sydney, Australia

[Mel]

Originally Posted by rhill

What is the +/- of the pistons,rings,wrist pins&caps in grams,I'm going through this now and I'm within two grams,2 even,1 one gram heavy,1 one gram light.

It's been a while, but if I remember correctly, Lycoming's limit is 7 grams max delta.
Remember, this is a low RPM engine and while the better balanced the better, it's not as critical as on a higher RPM engine.

[RV10inOz]

And nice low deposit pistons too

AA sent me your jug pictures...... Nice work! Makes all hose flat earth LAMEs afraid of heating humble pie.......CrowPie