A friend just bought a 150 that has a JPI. Several cylinders are commonly running in the 400 to 420 range (OAT 90+)

I'm debating between this 1) is a problem or 2) might be normal for a 150 and no one knows it because they are never instrumented. Comments?

That's too high. You can "jet" the carb by drilling them out with the numbered drill bit drill 1 or 2 sizes bigger than what you have. I think you'll find they drop to 330 or so. May need to lean a hair on take-off to achieve max power. This advice is for experimentals as I have no idea what is legal for a certified O-200; perhaps they sell certified carb jets. This is based off of 700 hours behind an O-200 that was instrumented.

My thought was inadequate fuel flow too

First thing I'd check is the mixture cable adjustment. Is it going all the way to the full rich position?

What's the EGT numbers?

Dave

I have been running an engine analyzer in my C150 for about 10 years. If I take off and climb at best rate to a cruise altitude of over a few thousand feet my CHTs will go above my self imposed limit of 370 DF.

If I enrich the mixture to get the temps down the climb is anemic. C150s do not have a 100 hp engine it is more like a 90 hp engine that is just too low for what is wanted. (Continental rates the 0-200 at 100 hp at 2850 rpm but by the engine is red lined at 2750 when installed in a C150.)

The answer is as soon as I am at 1,000 ft AGL I climb at 80 MPH it is slow but I get there. By reducing CHT the number of times I need to ream the valve guides is greatly reduced. A stuck valve will really ruin your day.

What type CHT probes are installed? What phase of flight? What is the EGT?

Flying that Tiger last week in Arizona Summer temps I was getting 430-450 on a few cylinders. I could richen it up and drop them but blowing through a lot of gas.

Leaning the old fashioned way till it got rough and then richen in a bit resulted in some toasty temps. I think in the past nobody knew (and they ran forever).

I kinda liked the old way of obliviousness.

Full rich, full throttle cruise (new cylinder breakin)

Charles,
Are all cylinders new and within the break-in period?

Sparkplug gasket type CHT probes (as I had on my last 150) tend to read a bit hotter (30*F maybe?) than a bayonet probe on the same cylinder. A new cylinder will typically run slightly hotter durring the break-in.

Just one new jug. I think #4

If I ran my 150 at full throttle in level cruise it would turn WAY above redline at lower altitudes, like 3000 ft msl.