#2 CHT Higher than the rest

[McPilot]

Originally Posted by lr172

Mike,

I did the mod to route more air directly to the lower fins on #2. That cylinder had been running about 20* or so hotter than the next two. I did a test flight yesterday and #2 was the same as #4, so the mod dropped the temps about 20*.

Here are two pictures of the install. You can't see it, but I cut out a rectangle in the baffle about 3/4" high and covered most of the horizontal area of the cover. I am not sure that I need to route air to the upper fins, but did anyways. the holes in the top were 1/4". I figured that I would keep these minimal and drill more or larger as necessary. Overall, it was a simple mod. I chose not to remove any baffling and used rivets on top and just RTV below.





Larry

Thanks Larry,

This is a great help. I am at the airport now getting ready to do this... I can see that 3/4 cutout through the holes you drilled..
Thanks again! On top, my baffling actually has a stiffener "dam" in the area that has the problem with the fins. The left side facing plane does not have this dam. The cylinder fin profile is different on that side as well....

I will let you know how this works.. THANKS!!!

Mike

[DanH]

Larry, that's really very clever! My compliments....

[LettersFromFlyoverCountry]

I didn't see any mention of the air dams in this location and whether you've cut them down.

[lr172]

Originally Posted by DanH

Larry, that's really very clever! My compliments....

Thanks! It's really just an extension of pioneering work you and others have done on #3 airflow fix. That's the beauty of this community. As we share and learn, others can leverage that, as well as expand the knowledge or use cases.

Larry

[McPilot]

OK guys..

Here is what the EASY fix was... I used a spacer about the thickness of 2 washers behind the baffle attach point on the #2 cylinder.

All of my CHTs are with a few degrees of each other now.

I am not so worried about a baffle leak as it does not appear to be clinically significant..

The OAT was 80 deg F in flight
Happy Cylinders:

[alpinelakespilot2000]

Mike, so far so good, but have you checked what happens to the temps when you are leaned out? That 10.6gph looks like a pretty rich setting. My numbers will vary significantly at different mixture (and throttle) settings.

That said, I made the same similar change first offered here on VAF for #2 by Toobuilder and it really helped my #2. Unfortunately not so much with my #3 which has always been my problem child.

Good luck as you test further.

[McPilot]

Originally Posted by alpinelakespilot2000

Mike, so far so good, but have you checked what happens to the temps when you are leaned out? That 10.6gph looks like a pretty rich setting. My numbers will vary significantly at different mixture (and throttle) settings.

That said, I made the same similar change first offered here on VAF for #2 by Toobuilder and it really helped my #2. Unfortunately not so much with my #3 which has always been my problem child.

Good luck as you test further.

Hi.. Good eye.. Yes, I was running at ~70% power and fuel flow was ~9.7 All temps below 360 throughout the flight... I notice my fuel flow creeps sometimes...

[artrose]

I had a similar situation with #2 on my carbed O-320. I read everything I could, and asked everyone I thought might have an answer. I checked for a sensor problem first. I tried several different modifications to the inlet ramp, sealed every hole and crack, assured myself that the baffling was as good and correct as possible. I installed bell washers between the rear of #4 and the baffle wall. Nothing I tried was working. Then, one day I was looking at the baffling on my friends 8. He had a small 1/4" gap between the baffling lower inlet ramp and the front of cylinder #2. Mine was flush up against the cylinder. I opened up that 1/4" gap on mine, and it worked like a charm. Obviously a certain amount of air can now flow down thru that gap and cool the forward lower portion of #2. Issue resolved. It only took 3 years of fiddling and step climbing to figure it out.