Run-in

[JRobb]

Run in issues resolved

 

[Magman]

Can you elaborate more on the run-in procedure?

This does sound like a real mess.

Was the Dry Lifter Clearance checked?

If the clearance was excessive it may reduce transfer from the Lifter to Pushrod

to Rocker Arm and result in wear.

Where are you finding the metal?

 

[JRobb]

Run in issue rsolved

 

[Magman]

It sounds like the entire run-in procedure was severely flawed.

Running on a stand usually involves a Test Club, Scoop Cowling and complete

instrumentation.

If the Rocker Arm Bushings were worn out there are major issues.

Does the shop involved regularly overhaul engines?

 

[Gary Ward]

I just went through an extensive overhaul (0300a) and the engine has been making metal (brass) through the run-in process. Most of the engine parts have been replaced and those that were re-used were sent off/approved for use. I also installed all new millennium cylinders, a spin on oil filter, high output alternator, overhauled mags, new wiring harness, and a new sky tech starter. After 3 initial runs, we decided to remove the rocker arms, which were re-bushed and reamed. 10 out of the 12 showed ware close to limits, which is very alarming after only 3 hours of run time. The thought is that the oil pressure is too low and not providing sufficient oil to the rocker arms. The shop is going to re-install the rocker arms and adjust the oil pressure spring to provide more pressure, then run again. The oil pressure on the runs was on the low side of limits and the runs spent more time at low RPM than high. This was due to the original propeller being used instead of a blank, which caused the CHT to quickly reach the limit. If increasing the oil pressure works, we’ll re-bush the rocker arms and move forward.

Other bad news was the possibility of having to replace the main bearings in the crankshaft. I talked to another shop and they said if I didn’t, they would aggressively wear in 100-200 hours due to the metal impregnating that has already been done in the run-in process. I’m incredibly concerned, as this may lead to a total tear down and a lot of money. I’m not sure if that is a cause for concerns at this point. Any advice or insight would be greatly appreciated!

So sorry to hear this.

IMO, it will be necessary to disassemble the motor to clean it after you find the reason for it making metal.

I don't need to know who does your motor work, but you might want to re think it?

I am sorry for you.

 

[Bell206]

through the run-in process.

After 3 initial runs,

So to clarify, you are performing the "run-in" portion of the engine OH per what reference? TCM SIL 012?

we decided

The shop

WHo is we? Is this a repair station?

extensive overhaul

having to replace the main bearings in the crankshaft.

may lead to a total tear down and a lot of money.

Don"t quite follow your post. Was the engine overhauled per the TCM OH manual? And are you stating the engine wasn't a "total tear down" for that overhaul? Given you are still in the OH "run-in" process and the engine hasnt been approved for return to service, why is the maintenance provider pressuring you to pay for more work when they havent completed the original OH work?

 

[Bell206]

I know they’ll do what needs to be done to make it right, but it’s frustrating.

This is the important one. Imagine how frustrating it is for the mechanics as well. Good luck.

 

[Magman]

It sounds related to the oil system.

My recall is the Flight Range Oil Pressure is 30 -40 psi.

There is also a Minimum at Idle Limit of something like 5 psi.

Were the higher power runs conducted @ 30 or 5 psi?

The actual cause may be something minor like a chip in the Relief Valve or

a weak spring.

Another culprit could be incorrect placement of the gasket for your

new oil filter.

 

[strangebird]

Did you inspect the oil pump and gears in the accessory case.?

Flush out the oil lines and get a new oil pressure gauge to see if you are making accurate oil pressure.

None the less the engine shop should be doing all to fix the issues, you should not be guessing what is wrong, don't pay anymore until you are
Minimum oil pressure is 10 lbs on 0300

If you want some very knowledge people go to the cessna170 site they all fly 0300/ c145 engines mostly, these engines are not rocket science

 

[Dan Thomas]

Brass in the filter and rocker boxes is a very bad thing. Brass is not supposed to be used for bushings. Where did those bushings come from? Some obscure aftermarket outfit?

Bronze is the stuff for bushings. There are various grades of it. Brass is an alloy of copper and zinc and has a bright yellow color, sometimes a bit red if the copper is a higher percentage. Bronze is copper and tin and is darker, more brown than yellow. A machinist could spot the difference instantly. Find one and ask him. Brass is great for hose and tube fittings, not so great for bearings.

If the engine has a spin-on filter there shouldn't be much debris getting to the bearings. Any overhauled engine is going to make some metal and you don't want any of it reaching any moving parts.

 

[Dan Thomas]

This is my mistake. It must be bronze. The rocker arms were re-bushed and re-faced by an external company. Not having a maintenance background, I’m likely to get some things confused.

I’ll post an update when I have more clarity.

There are also small oil passages in the rocker. They lead from the pushrod socket up to the bushing, and the bushing has a hole in it to get the oil between it and the pin. If the bushing's hole isn't lined up during installation, the bushing runs dry and wears quickly.

The valve guides are also bronze. If they're replaced, they're reamed to size after being pressed into the head. If the people doing the reaming don't thoroughly clean up afterward, you could have bronze chips laying around. Bit of a stretch, though, considering that the cylinder is handled many times between that process and being installed on the crankcase.

 

[Magman]

So.

Complete Major Overhaul.

After 120 minutes of running the decision was made to remove the Rocker Arms

which were found severely worn and they were then rebushed and reamed.

What prompted this?

Usually I’ll leave all plugs out and spin prop by hand till I get an indication

of oil pressure.

Activating the Starter will normally put the OP in the green.

Why the Run Schedule would continue with minimum OP is beyond me.