I have changed nothing, and for the last 15 hrs or so #1 cyl is getting hotter.
While in cruise EGTs rises to about about 1,600 and CHT rises above 380 then I enrichen it and open a bit cowl flaps to have them under 380 the CHTs and EGTs under 1600.

#4 used to be the hottest cylinder, but EGTs never were as high as #1 now.



Checked the baffles and they are fine.

Any advice on what to look for?

Can you do a compression test to see if the exhaust valve is starting to leak?

Will have my mechanic do it on Monday
If the readings are low , how can I tell is from the valve?

Listen to the leak:

Exhaust pipe = EV
Induction = IV
Dipstick opening = rings

If it's a Fuel Injected engine it could be a dirty injector.

Clogged injector = fuel pressure spike too. AKA fuel flow. (PA23-250C)

Barnstormer wrote:If it's a Fuel Injected engine it could be a dirty injector.

O 470 R carburated

Intake gasket on #1 has cracked and is starting to leak.

Neb12 wrote:Intake gasket on #1 has cracked and is starting to leak.

+1 - That's where I would put my money...

Easy fix...

As was mentioned induction could be your problem. If not I would suspect exhaust valve guides having lead/carbon build up, might be worth running some Avblend in your oil. Fuel additives that help clean carbon deposits etc are helpful. Would be a good idea to bore scope the cylinder and see what's going inside, particularly with the valves. Are you getting oil blow by in the cylinder/oil on the bottom spark plug? Rough cold starts?

Might not be a bad idea to run the cylinders kinda hot for awhile shooting for CHT temps in the 375-395 range, that will help scavenge any lead/carbon build up in your valve guides etc. I run LOP on my 0-470 most of the time and have found that running cool 300-330 CHT all the time seems to cause an increase in lead build up. My solution has been to run 100+ ROP at higher power settings and get the cylinders up in that 375+ range every now and again, haven't had problems since, oil/fuel additives have been helpful as well. Keep us posted, curious what it turns out to be, hope its something simple.

Skalywag wrote:...Might not be a bad idea to run the cylinders kinda hot for awhile shooting for CHT temps in the 375-395 range, that will help scavenge any lead/carbon build up in your valve guides etc. I run LOP on my 0-470 most of the time and have found that running cool 300-330 CHT all the time seems to cause an increase in lead build up. My solution has been to run 100+ ROP at higher power settings and get the cylinders up in that 375+ range every now and again, haven't had problems since, oil/fuel additives have been helpful as well....

What Skalywag said. My same experience with the IO520.

Usually I ran CHTs between 360 and in the 370s.
Im running auto fuel, also use Camguard
Dont know what are the effects of this combination regarding carbon build up.

I do agree is a good idea to boroscope.

No rough cold starts, no oil blow either.
I also hope is something simple.

No test was needed, clamp for Cyl #1 was loose and we could even see some fuel stains.

Replaced clamp re tightened , clean and good to go .

Thanks very much for all the advice.
Im glad was a cheap and easy fix