Rejecting New Parts?

I am about to embark on a field overhaul of an IO-540-AB1A5. The donor engine belongs to my hanger mate. He purchased the airplane new 17 years ago, it has no damage history and currently airworthy (although it has reached 2,100 hrs).

I have a list of mandatory parts required for the overhaul. During the process I will be upgrading it to 260HP -D4A5. That requires new counterweights, rods, pistons and pins. I'd expect it will get a new cam and cylinders as well.

I read an article by one of the engine shops, that they habitually check all new parts for dimensions before installation. The point that really caught my eye was that they reject 30% of new cylinders. Can that really be correct?

Installers responsibility

It's the installers responsibility to make sure everything is right,thus inspect everything twice,install once.there is a great thread about cleaning the oil passages before installing the plugs.When your paying $1200 plus for a cylinder kit and you don't like the grind or the taper,I'd be sending it back also.This had to do with reground tappet bodies " it all comes down to how fresh is the face of the cutting stone and how often it gets redressed."I would think the same thing will apply to cylinder bores,if they finish cut ten at a time,better to have 1-4 then 6-10.It's the difference between an engine that goes to TBO and beyond and one that needs a top at 800 hours.
RHill

rwtalbot said:

I read an article by one of the engine shops, that they habitually check all new parts for dimensions before installation. The point that really caught my eye was that they reject 30% of new cylinders. Can that really be correct?

Click to expand...

Yes, at times it has been all too true.

Measure everything. Do trial assemblies. Assume nothing. You might get 100% middle of tolerance, or a few real surprises. There's no way to predict.

Right now I'm about 8 weeks into a problem with unsatisfactory crank/camshaft gear mesh in a popular alternative engine. It happens.

that's Barrett. He seems very *n*l retentive, which is the personality type I want working on my engine!

and my engine guy has seen new Continental jugs that did not have the right valve springs!

A mfg is trying to pass every part they can, cause it is $$. So anything that is borderline but not specifically defined by a number they will likely pass. When a builder rejects parts he is only thinking of reliability because the mfg takes the financial hit if he rejects it (provided they accept his rejection and that might depend on how many jugs he buys).

Check Everything

Its a good idea to check everything.. 30% seems a bit high to me but something will crop up when you least expect it. Cylinder issues are common but usually nothing that cant be fixed prior to assembly.

30%

We do not currently reject 30% of cylinders that come to our shop, but at one time we certainly did. There was an issue with a key hole in the barrel that caused brand new cylinders to come off the dyno with no differential compressions. That was several years ago, but that is why we dimensionally inspect parts and dyno test every engine. It's all part of our quality control process.