I have been happily flying my experimental for over 200 hours now. The airplane has been a joy to fly. One thing that has been an nuisance is my #3 CHT. It oftens runs extra hot compared to other cylinders, especially in summer time. It hangs out around 385-390F while the others are 350 and below. In an extended climb, #3 will go up to 425F-450F pretty quickly in the summer. I have been trying all kinds of fixes, like ramp angle, extra outlet air, etc. None were very effective.
I have the RV baffles on my Cub. In talking to some folks at JC, it seems that RV baffles run hotter than the stock Cub style baffles. I would imagine this is because they are tuned for a 200mph airplane and not so much Cub speeds. None of my friends with stock style baffles said they had a cooling problem. As I looked at various Cub baffles, the only major difference I could find was around the #3 cylinder. I don't have a cooling problem with my other cylinders. The RV baffle is angled and pulls in very tight around #3. So I modified my #3 RV baffle area to be more like a stock Cub, which is more boxed and has around a 2" air gap behind the cylinder.
I tested my modification yesterday and the results were immediately evident, my #3 CHT now is about 30-35F cooler. In fact #3 is no longer the hottest cylinder, #4 is 2 or 3 degrees hotter. During an extended climb, both #3 and 4 stay below 400F. So I was very happy with this modification. I posted this mainly to help those with experimentals who want to run the RV baffles and still have good cooling performance. The RV baffles are around $500 cheaper than the certified kits.
To modify, made a vertical cut in the rear baffle to seperate that section behind upper cylinder. I then flattened the rear baffle, added some sides/ducting, riveted closed. Siliconed the joints. It took me two evenings to complete. Would be a lot easier to modify if the kit wasn't installed yet. Hope this info helps!
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