The International Cessna^® 170 Association

Stay as low as possible, just run around the pattern at full throttle and at pattern altitude as previously advised. Stay within gliding range of the runway until you feel comfortable with the way the engine is running. Ground running and low power operation of the engine can glaze the cylinders with oil coke and they might never break in.

Maximum manifold presure yields maximum cylinder combustion pressure and that is what seats the rings. Full throttle is the best you can do. Don't worry about the bearings, seals, other moving parts, they are in as good shape as they ever will be right after the zero-time overhaul you described.

Wow! I've never seen such a consistent answer on this forum to date. Ok, ok...I'll go fly it. Jim Musgrove also said the same thing... I guess I have been so worried about engine Nr 2 being a lemon, too, that I have been focused too much on that. I'll get the rest of the pieces back together, paste the annual in my book and get off the ground. Thank you all for pulling my head out of....

Shawn

The sand?

In keeping with the PG rating of this forum...sure, sand...

Lots of us have had many occasion to pull our own head out off the sand so we recognized it half again as fast as those that haven't.

I also agree with the break-in advice.
Just a comment about the oil fouled plug: A cylinder sits above the oil level of the engine sump. (Oil from the sump will not migrate into a resting cylinder.) A cylinder which has a lower oil fouled plug is likely one of two things. 1- A poorly fitting or broken valve guide or valve. (The valve guide allows oil to seep from the rocker-box to the cylinder interior via a defective/poorly-fitted valve guide-to-valve clearance.) or > 2- A broken or improperly fitted oil-ring. (Such a ring will not scrape excess oil off the cylinder walls and will allow too much oil to remain in the upper cylinder. In such cases, it is usual to also observe a lot of carbon on the upper plug from burning oil, or to notice oily-soot on that side's exhaust tailpipe/area.)
If the condition continues past a few hours operations, then the answer is the same: The cylinder must be pulled for repair.

Geez George, you're a real buzz killer... I will try to get her up soon to see if it is just a new ring that needs to seat correctly. I'm going to assume the latter, being rebuilt and all. But if after a few hours of real work and the problem persists, I'll know where to look. Thanks!

I would pull the rocker box cover off and, while pulling the prop thru, observe the valves operating. Look closely at the valve stems where/as they slide up/down the guide with the ordinary side-ways pressure the rocker-arms supply as their arched-ends slide across the valve-stem tips.
At various points of the valves positions, I'd attempt to "rock" or move the valve-stem sideways to determine if there's any chance of a cracked valve guide. (New guides may be cracked during installation, and/or may be reamed escessively.)
This can be tedious, but it's a good check to make. (It's easier with the valvesprings removed, but a bright light and a discerning eye can pick up on the stem-movement.) A cracked guide can lead to in-flight failure.

gahorn wrote:A cracked guide can lead to in-flight failure.

That would really be a buzz killer. That sounds like a good idea that should be easy enough to do during a day. Question: If the valve guide were bad, wouldn't the engine run roughly right from the beginning? It seems to me, the engine expert that I am that with a clean plug it runs well, then as time goes on it fouls and then it just gets worse. Thoughts?

spduffee wrote:

gahorn wrote:A cracked guide can lead to in-flight failure.

That would really be a buzz killer. That sounds like a good idea that should be easy enough to do during a day. Question: If the valve guide were bad, wouldn't the engine run roughly right from the beginning? It seems to me, the engine expert that I am that with a clean plug it runs well, then as time goes on it fouls and then it just gets worse. Thoughts?

My 206 (with IO-520 engine) ran so smooth you wouldn't believe it...but it dropped oil on the ground after shutdown (fuel injected engines have induction drains which dropped the oil on to the ground which collect there due to bad guides.) In troubleshooting the oil in the induction and fouled plug...we discovered the cracked guide.