Help Understanding the Baffling Mod
 

I have searched and found all of the threads regarding adding space behind cylinder #5 on the RV-10 so that that cylinder cools a bit better.

I have seen the idea of modifying the baffle with a hammer and with a little aluminum modification.

But, I have not seen a picture of the simple solution, adding a washer as a spacer.

Does anyone have a picture of that ?

I have managed to get all of my CHTs down quite a bit, except for #5, which has been stubborn.

360 vs 540, but the same concept:

http://www.vansairforce.com/communit...asher+cylinder

The root of the problem is that lycoming cylinders are designed to work together, with one cylinder providing the air path for both. In that respect, the washer trick fails to fully address the real issue and creates new ones. Calling the washer trick a "solution" is like saying a mini spare on your car is the "solution" to a nail in your full sized tire. It gets you where you want to go, but the car will not perform as designed.

Good analogy Mike.

options
 

so you guys don't like the washer. can you share your preferred methods?

Here is one way, but the baffle would have to be removed for this. It provides air to an additional 15 in^2 of fins. The flashing should be removed and head polished at the same time. Why have the fins and allow them to be blocked off? This provides a .2 X 2" slot for air flow, at 5-15 in-h2o pressure that is a lot of air directly applied to cooling.

This is what I did when the washer didn't do the trick. I was actually able to do it without removing the baffle on my o-320, but by the time I finished it would have been just as quick to remove it. Brought temps right in lone with the others and can climb all day now.

Chris

A search for "... #3 cooling..." Will reveal a plethora of threads on the subject, but Bill's solution is the jist of it. In addition, both DanH and I in particular have worked the issue and posted results.

There are two or three excellent threads to review, showing a variety of bypass ducts like above. Those ducts can also be found on some certified airplanes.

Next on the list is a strip of sheet or plate material where the washer would go (screw goes through it). That spaces the baffle tin out away from the head like the washer, but blocks the large (and useless) leakage area in the immediate vicinity of the screw.

Last is a washer, and a wad of silicone to block the useless leakage area.

The latter two also result in some leakage out the sides of the lower wrap, while the duct keeps the wrap hard against the tips of the lower fins, assuming a little care.

I did the plate method that Dan describes, initial tests shows it works.