Help with #1 low CHT - or is it ok?

[Ragsf15e]

I've only had my "new" bird for about 2 months, so I'm still getting use to her, but I've noticed that the #1 cylinder runs much cooler than the other 3.  Like 50+ degrees cooler.  Is this ok?  Is it just because it's up front and getting the lion's share of the airflow?  Is something wrong?

 

I've got a 1968 M20F.  The engine has ~590 hours SMOH (but it was 15 years ago).  It was modified with GAMIs about a year ago (~.4 spread).  I've been running it ~20 LOP once I get up to altitude and it seems to make good power and is smooth.

 

It has an EDM-930 which I downloaded and will post my recent flight which was just tooling around the local area (up to 6,500) and then a few night patterns.  You can definitely see that #1 is much cooler from start all the way through the flight though.  #2/#3 are usually about the same and much hotter than #1.  

 

I set the graph bar to a time when I had it leaned for cruise so the temps on the upper right were fairly stable.

 

Any thoughts?

[Andy95W]

The next time the cowling is off, check to see if #1 has the same type of CHT probe as the others. With some engine monitors (not sure if the 930 falls into this category) the original CHT probe had to stay in place and a gasket type probe had to be used for that cylinder. Those types of probes read cooler than the others, by about 50 degrees.

If it's making good power and is smooth, I'm not sure I would sweat it short term, but it would be nice to figure out by your next annual.

[Ragsf15e]

Andy - That would make sense.  I'll take a look at the probe type next week while changing the oil.  Thanks!

[N601RX]

The 930 is a primary monitor and comes with 4 new probes which are all the bayonet style and mount in the factory holes.

Some have a strip of aluminum along the front edge of the front cylinder that is used to balance air flow to the front and rear cylinder. There is a service bulletin that describes it.

[The-sky-captain]

I've had my J since 08' with close to 1200 hours on her in that time as well as an overhaul around 600 hours ago. My #4 CHT has ran about 30-40 low before and after the OH from day one so I wouldn't be that worried about it. I've got the EDM 730