Since installing a JPI EDM 930 earlier this year I have noticed that my number 6 cylinder has been running 50-80 degrees cooler than the hottest cylinder. EGT is about the same as the others but CHT is always much cooler. Someone suggested to me that there should be a bit of baffling in front of number 6, just like the oil cooler in front of number 5. Mine is a stock O-470R in a 1974 Cessna 180J model. My mechanic says that there isn't anything listed in the parts catalog for my serial number that would indicate the baffling is missing. The temperatures say differently, but now I don't know what to think. Does anyone have any idea whether I might be missing some baffling up front that would explain the much lower CHT in number 6?

Bear in mind that these big Continentals with carburetors are really challenged at fuel/air distribution.....long induction tubes, and all that.

Do you have your forward crossover induction tube insulated? Simple pipe wrap insulation tie wrapped on that crossover tube helps keep the engine happy in cooler temps. Won't hurt in warm temps, but I don't know if it'll help your issue. But, if you don't have that crossover tube insulated, I'd do it.

Also, try using partial carburetor heat and see what that does.

One more question: Have you checked the # 5 probe to verify that it is in fact accurate?

In any case, I don't think what you're seeing is anything to worry about. Sometimes, installing an engine monitor simply highlights things that have been there all along and may in fact be completely normal. Unbalanced fuel/air ratios are something of a way of life with these engines.

MTV

I thought they all had a baffle on #6?
Here is a pic of what I have, mine runs warm on #6, I need to trim some of the baffle off.

Interesting. So clearly some Skywagons have the baffle and some don't. Anyone have any idea what distinguishes those that do from those that don't? Is it something simple like an engine upgrade from the stock O-470? Mine is stock and I suspect number 6 has been running cold since day 1. It may not be in the parts catalog for my serial number but the evidence is clear that a baffle would help to bring all CHTs into line. As for the cross-over tube, mine is installed with insulation. In addition, although O-470s have a reputation for uneven mixture distribution, mine runs smoother than most. Now that I'm aware I'd just like for all cylinders to run the same, or close to the same temperature.

If you haven't done so I would try swapping senders from another cylinder. Sometimes QC isn't as good as it should be.

Then when temps are verified worry about the rest,
Go through the parts manual to make sure you have correct baffling etc.

When it comes to CHT temps every aircraft is different. There will be trends with identical models but they all vary. Your temp spread will also vary with outside temp/workload. Proper baffling can be used to regulate the CHTs to a point. I would use aluminized tape on the front cylinder to start with so you know how big of a baffle you need, and fly it for a while with the tape to make sure it fits your year round mission.Adjust the tape in 1/2 inch increments until you have what you want. As you warm the front you will cool the rear!! Then make a metal baffle that size. This is a pretty simple procedure If you IA says it cannot be done than might be time to find another IA. It is hard to get them all the same with a carb but baffling will help.
DENNY

Additional thought on the topic. I do not think you are missing any baffling, I am just saying that adding some should help.
DENNY

Over the few hours I've put on the 185, I've noticed that my #6 is running about 80 degrees cooler (CHT) than the others, notably #1.

I came across this thread, and a similar thread on the type club forum, and came to the conclusion that I'm missing some baffling in front of #6 and #5. In fact, it appears there was once some tape applied to #6 as evidenced by some adhesive residue on the cylinder itself.

The baffling that was once in front of #5 was evidently removed with some left handed children's safety scissors... The remaining aluminum sheet behind the oil cooler has a jagged edge that doesn't look like it broke, it's just gone.

So I've got some experimentation to do as to how much aluminum plate to add in front of #6.

I'm curious though as to what to do in front of #5. I've read of guys putting aluminum tape over part of the cylinder, and others have built a curved aluminum baffling that directs air over the top of #5 to the rear of the cylinder.

My #6 Cylinder


My #5 Cylinder


More Information

For some reason the additional pictures I had to post here get rotated when I drop them in a post. But there are pictures of hand written notes and a photo of typical CHT/EGT numbers.

https://backcountrypilot.org/me/my-photos/6013slippery-wing/album?albumid=5714

On the cub I used tape for over a year to make sure I had it right then made metal piece same size.
DENNY

I have an 0470-L. My #6 had run cool like yours did since the day I bought it. Its baffle looked pretty haggard.
I fabricated a new one that was about an inch taller. Well, that helped but it was still cool. I extended it again
another inch and bingo. That did the trick. That's all it took for mine to balance out. I'm really happy with it now.

My '76 185 also had a very cool #6. Sometimes less than 300f.

Like Denny said above, I used aluminum tape on the front of #6. Initially it was a tad too much, but I removed 1/4" or so at a time until 6 & 4 were even. Eventually, I'll fab a new baffle and remove the tape.

The stock baffle on #5 is amazingly big. It extends almost to the top of the cylinder (when viewed from the front like your pic). It's dead-on, though. 5 & 3 on my plane are always +\- 5F.

My coolest cylinders are 1 & 2. Usually 30F or so cooler than the rest.

Cannon wrote:The stock baffle on #5 is amazingly big. It extends almost to the top of the cylinder (when viewed from the front like your pic). It's dead-on, though. 5 & 3 on my plane are always +\- 5F.

I've seen pictures of that baffle for #5, and you're right it's surprisingly large. I'll see if I can find those pictures and fabricate something similar. In the mean time I'll start experimenting with some aluminum tape.

Thanks, fellas.

This is what my number six looks like on my O 470K. It is a modified 470A baffle that I have used since 1995 when I switched engines. I don't have a 6 cylinder EDM etc but have never had a problem with number six and it generally looks like it runs cooler and richer than the rest when a plug is removed.

When i bought my 182, it looked the same - baffling missing. That plug was black from probably running cold. But really what happens is it vibrates and cracks and it keeps getting trimmed back to get rid of the cracks until you have nothing. I bought the new baffle piece from airforms in Alaska. Simple install, couple hundred bucks. The "glue" you see is not from tape - you high temp silicone the back of the "intact" baffle to the head to try to prevent vibration cracks.

https://www.airforms.biz/