EGT selection - Question for Mike Busch (or others in the "know")

I own a Cessna 140A and it is equipped with a single cylinder Westach EGT that is not working. I am uncertain if it is the probe or the guage but I purchased a TSO'd new guage/probe for about $150.00.

I recently watched Mr. Busch's Webinar on EGT/CHT (and I remembered a key learning that went something like: an EGT is good for diagnosing engine problems but a CHT is better for determining mixture and proper leaning.)

So, my C-90 has less than 150 hours since overhaul and I want it to last. I rely on those who know more than I. I understand the concept of leaning, but apparently the EGT will be of little help. I have erred on the safe side (I thought) by running full rich while flying (typically at 3000' or so MSL).

So here are my questions:

1. Would you recommend a 4 cylinder EGT/CHT replacement guage for the single cylinder EGT? Is it cost effective?
2. Keep the single EGT? and lean the motor until it runs rough than en-rich the mixture until it runs smooth? (but avoid the little extra)?
3. Other?

Thanks,

Daniel

Thanks

You will find differing opinions here and that's OK, this is just mine.

Not a lot of reason to have an EGT on all 4 cylinders with a carburetor or a single point injector such as an Ellison. With an injected engine that utilizes nozzles for each cylinder it is a valuable tool for alerting the pilot to a dirty or partially blocked injector nozzle. Personally I would go with #2. I would take a plug reading and install the probe on whichever cylinder showed any tendency to be leaner than the others. Just make sure the engine is in good order when you make the decision.

Neil, I could not disagree more with you about that. If one of the cylinders in my Cessna T310 swallows an exhaust valve, I continue to the destination thinking about how much it's going to cost to repair. If the C-90 on Daniel's Cessna 140a swallow an exhaust valve, he will most likely wind up making an off-airport landing. So the less sophisticated and redundant the aircraft, the more the need to have good engine instrumentation to make sure everything is working right and (more importantly) to give early warning if something starts working wrong.

Without question, I would recommend that Daniel install a 4-cylinder digital engine monitor like the JPI EDM-700-4C or EDM-730-4C. This is NOT as a leaning aid, it's as a condition monitor and troubleshooting aid. I personally would never own a piston single without installing this kind of instrumentation. --Mike