FINALLY! My Overheating Cylinder Head Temperature Problem is FIXED!!! What Was the Cause?

Wow - The fact that no catastrophic damage was caused by this much advance over quite a bit of time is testament to your discipline in monitoring CHT and backing off power and maintaining full rich when required. It is probably an industry standard that manifold pressure sensors send a higher voltage at higher pressure, but this would have been such a more benign failure mode if it would have failed the other way resulting in no additional advance at low power. I wouldn't want to long term fly a constant speed prop without the manifold pressure sensor as it would negate a lot of the advantage of electronic ignition. But with a fixed pitch prop most of the time engine RPM is a good indicator of engine load. And, maybe not critical when it is off a bit descending at low power with the prop windmilling.

That must be such a relief to have this finally solved. 👏

I had high CHT issues, (slick mags), when I finished building my Vans RV7A. Cyl 2 and 3 temps ran about 430 in climb. My issues ended up being the baffles. The cylinder fins on the Lycoming and the cylinder wall merged on the same plane, if that makes sense, which stopped any airflow at that point. After seeing post on VAF about this, I put in a couple channels to allow air to get by and bingo... took off on a hot summer day here in South Alabama and did a full power climb all the way to 10K. CHT max was now about 375 and with increasing altitude ---> cooler air ---> engine making less power as we climbed the temps were coming down.  Yes timing advanced as you were experiencing... like you said could have caused damage! Great video Scott.

Glad you found the trouble, as a over heating eng is never a good thing. That could led (as I've sure you know) to brunt value's, holes in pistons even bent rods.

My friend you are amazing. I know that us regular humans would have ever got it fixed and I doubt most shops would have either. Congratulations most informative and entertaining

Congratulations, Scott! Your tenacity paid off. 😉 So glad you figured it out.

Awesome! I’m sure it feels great to have that issue behind you! Great persistence on getting it fully resolved! Fly safe!

Great news ! So glad you finally isolated the problem ! Keep flying and keep the videos coming 👍😊

Hey Scott, how fortunate you re to be able to diagnose the problems and do a fix. Kudos!

I had left the master switch on several times until an older friend told me to leave the rotating beacon or strobes on, like you that has saved a me from a dead battery several times! Enjoy your method of problem solving the over temp on the CHTs. Cheers

Finally a fix! I have the same ignition system and same problem. But I already disabled the vacuum advance and it made no difference, bummer. I still suspect the ignition system but it's so hard to check the base timing on a pusher!

What a journey ! thanks for taking us with you , you are a real problem solver❤

Glad that's fixed. Now for the propeller performance comparison. Thank you for documenting your work.

Good to hear. Now consider this. Your Mag timing was 32° BTD which is much closer to what you stated as the desirable 35° BTD for the elec timing. It seems to me that both ignitions should be timed the same for cruise flight. So maybe that was the reason the mag was at 32°.

My employer owns a Velocity with Franklin engine that had CHT issues as well. It had dual Light Speed ignition boxes one had bad internal manifold sensor the other had similar issues. Finally got tired of always chasing ignition problems and found 2 magnetos, no issues since.

Just fantastic work Scott! Learned so much watching your videos.

Thanks Scott. It just goes to show us all, how important it is to know the fine details of avionics engine technology. Also the ability to measure, monitor and control this.

Hi Scott, Excellent Work. Thank you so much for sharing your process and the results.

Nice! With the ending temps, you should have a happy engine for a long time. Good call with Savvy data analysis. Fly safe! RD A&P, IA

Great find Scott!