Well, since paying the baffles a lot of attention my spread is still similar, but about 20 degrees lower. Went to the Bahamas over thanksgiving and only once did my hottest cylinder touch 400. Will have to keep tweaking but at least it’s improving!
It was in the summer, outside temperature 20 degrees C. Climbing from approx 300 feet to 5,000 to avoid some Airspace, climbing 90-100 Knots. (Perhaps once I climbed at 80 Knots which is probably when I saw the 430 degrees)
I’ll be looking at the baffles at the Annual – Thanks!
Archer 181. What is the OAT and altitude at ground level? Also what airspeed are you climbing out at when seeing the 430 temps?
I see a similar CHT spread; IO540-C4D5D.
Note that CHT scales with OAT, and roughly 1C OAT = 2F CHT, so a difference in OAT from 0C to +20C is about extra 40F on the CHT…
I usually manage to run my O-470-50 below 400 in climb, sometimes as high as 420 but that’s rare. It’s always one or two cylinders, most remaining much cooler. In cruise my cylinder 4 usually sits at about 390 with all the rest 345 – 380. A bit frustrating.
Also which is the hottest cylinder, varies. Mine used to be #6 and now (since the baffles were fixed some years ago) it is #3.
It’s quite common I think with carburetted Lycomings – one cylinder of mine always runs hot, and we completely renewed the baffles a few years ago (which helped a bit), and they are in good condition. We also had a small mod done to the cowling to improve airflow. That cylinder also has the highest EGTs as well which indicates it has to do with mixture distribution. The mixture distribution in carburetted engines is far from perfect so you do what you can do, but other than that – all I can do is reduce power in the climb to keep the CHT from getting too high. The same was true of the Grumman Tiger my wife owned in the United States – despite baffling in good condition the (carburetted) engine had one cylinder that ran hotter than the rest by a good margin (and had a higher EGT in the climb) – I think the same one as mine (she had a CHT probe on every cylinder, I have only probes on the back two).
I suspect most people never find out on carburetted engines because there’s either no CHT probe at all (my Cessna 140 didn’t even have an EGT probe let alone CHT), or just one probe as standard – but I bet most of them have quite a temperature spread between the coolest and hottest CHT.
To the OP: I have the same problem in climb-out with my 180 HP carbureted Lycoming. 3 & 4 cylinders go over 400 regularly. I climb to altitude in steps, throttling back and flying S&L for periods to keep the temperatures under control. But there is no realistic way to climb without going over 400. I would love it not to be so but it is.
I agree that there may be issues with baffles which I may replace.
A small gap in the baffles makes a big difference to CHTs. Even 3mm gap between a (metal) baffle and the cylinder head fins can give you an extra 20-30F. For years, my plane would climb with 420F showing on a hot day. Nowadays it rarely goes over 380F even in Greece.
But also a big tip is to get the fuel servo (if injected) adjusted for the full rich fuel flow to be right at the top of the tolerance band. For example most TB20s are set to about 23 GPH, but if you set the servo to 25 GPH that drops the climb CHTs perhaps 30F. It has no effect on cruise flow because one leans for peak egt ot LOP. I don’t know if carbs have an equivalent tweak.
As an aside, I always find it amazing how some topics I start end up with lots of replies (like this one with 24 posts). Some do even better (like “How not to hand start a plane” with 71 posts.
That’s because you post on interesting topics 
The one I found quite amusing “How not to hand prop a plane (again)” was totally ignored.
I found the post. Yes; the timing must have been such that it got missed, and once a post ends up too far down, it gets lost, because way over 90% of people use only the Active Threads link. I tend to highlight such posts (if interesting etc) but sometimes I miss them too. I moved it to the existing hand propping thread – to here. It is a pretty scary video to watch…
Well as the OP I found it all very useful, so thank you all! I’ll help my engineer tidy up the slightly worn baffles at the next Annual and report back in 4 months.
As an aside, I always find it amazing how some topics I start end up with lots of replies (like this one with 24 posts). Some do even better (like “How not to hand start a plane” with 71 posts.
The one I found quite amusing “How not to hand prop a plane (again)” was totally ignored. Perhaps I need to find a 1930’s black and white cine movie on leaning techniques – that’ll be click bait for EuroGA.
