Hot cylinder solutions needed

[Greg Ellis]

Hello all,

I have a 1963 C model with an 0-360-A1D.  Some history to help lay some context for possible solutions to my issue from you guys.  I had cylinder #3 changed out a few years ago.  The new cylinder was running very hot on the EDM 900.  For example, it would go from normal ground temps of around 290 or so after run up to 480 degrees by less than 100 feet after take off.  It would then cool off and run in the 420-430 range in cruise.  The mechanics could not find a cause for this.  They tried changing the probe on the EDM, tried moving it to another cylinder, etc.. etc... and nothing helped.  They then put a different style probe on it (what looked like a ring probe instead of the probe that goes into the cylinder) and that resulted in temperatures appearing to be normal.  I thought, and so did my mechanic, that everything was okay.

Fast forward, recently I had a compression check on the #3 cylinder and it showed zero compression.  When I removed the cylinder the compression rings were in multiple pieces and the piston looked black.  So we replaced the cylinder with a new steel cylinder (not overhauled).  The ring probe was put back on and I have been running things for about 17 hours for break in with everything looking good.  So just for the heck of it, I took off the ring probe and hooked up the regular probe that goes into the cylinder.  And now I am getting the same super hot temps on the new cylinder that I was getting on the previous cylinder.  I thought maybe the probe was bad so I bought a new probe and same thing, super hot temps.  I had cylinder #2 and #4 replaced at the same time and their temps are right in the mid to upper 300's as expected and they have come down and settled nicely during break in so I don't think these are hot temps just due to break in issues.

I moved the probe from #3 to #1 (known good cylinder with good temps) and it still shows it is running hot.  So I do not think it is a probe issue or an instrument issue although I have read about re-calibrating the EMD 900 but I am not sure if this is the issue.

So, where would be good places to look for something that can get the cylinder temps up from about 290-300 up to 480 before I am at 1000 feet in the air?

I am just trying to troubleshoot a little since it will be a bit before a mechanic can look at it.  And just to reiterate, #2, #3, #4 cylinders were all replaced at the same time and all with new steel cylinders.  #3 is the only one running very hot temps according to the EDM 900.

Thanks in advance for any advice.

[N201MKTurbo]

Have you checked the mixture distribution by doing a GAMI test? I know they aren’t normally done on a carbureted engine, but it would be good to know if that cylinder is running lean.

[Greg Ellis]

36 minutes ago, N201MKTurbo said:

Have you checked the mixture distribution by doing a GAMI test? I know they aren’t normally done on a carbureted engine, but it would be good to know if that cylinder is running lean.

I have not.  I will try that.  I have the instructions on how to do it.  Thanks.  Other than a possible intake leak what would other causes to a lean cylinder in a carbureted engine?

[hazek]

Sounds like your cylinder is definitely running hot. For a single cylinder it probably means too much air, or not enough fuel. Too much air could be an induction leak, not enough fuel could be a blocked nozzle. Has the nozzle been cleaned? Have you done the soapy water induction leak check? An induction leak can also been seen on the EDM data? Have you downloaded the data and uploaded it to Savvy? If so share a flight.

[Greg Ellis]

1 minute ago, hazek said:

Sounds like your cylinder is definitely running hot. For a single cylinder it probably means too much air, or not enough fuel. Too much air could be an induction leak, not enough fuel could be a blocked nozzle. Has the nozzle been cleaned? Have you done the soapy water induction leak check? An induction leak can also been seen on the EDM data? Have you downloaded the data and uploaded it to Savvy? If so share a flight.

Is there a nozzle to check on a carbureted engine?  I did do an induction leak check, I think on the first cylinder when it was running hot but I have not done one on this cylinder so I will.  I am just mystified that the same issue is happening to the same #3 spot with two different cylinders.  The intake couplers that join the intake tube to the engine were replaced, new gaskets of course with the new cylinder, etc...etc... yet seeing the exact same issue from two cylinders.  That is puzzling to me.  I have not tried a soapy water induction leak check but I will for sure.  I just recently downloaded the data but have not sent it to Savvy yet.  Was going to today but left the USB drive at home.  I will fly it this weekend and do that specific test (Mike Busch has an induction leak flight test) and then send it to Savvy and upload it here.  Thanks for the advice.

[skykrawler]

Unusual for a carbureted engine.  I assume your mechanic has checked the inter-cylinder baffling?

A massive induction leak would probably have you way lean of peak (on that cylinder) during cruise which lowers cylinder temps.

Detonation can cause high cylinder temperatures - and cause damage to pistons and rings.

Have you performed a magneto check at takeoff power while climbing out?   If a mag is cross firing to an incorrect cylinder nasty things can happen.

The other part of the system is the exhaust - make sure the exhaust stack for that cylinder does not have a blockage.

[Greg Ellis]

11 minutes ago, skykrawler said:

Unusual for a carbureted engine.  I assume your mechanic has checked the inter-cylinder baffling?

A massive induction leak would probably have you way lean of peak (on that cylinder) during cruise which lowers cylinder temps.

Detonation can cause high cylinder temperatures - and cause damage to pistons and rings.

Have you performed a magneto check at takeoff power while climbing out?   If a mag is cross firing to an incorrect cylinder nasty things can happen.

The other part of the system is the exhaust - make sure the exhaust stack for that cylinder does not have a blockage.

The baffling looks good and is pretty tight.  I even did the flashlight check that has been mentioned in other posts and could not see any source of air leakage.  I have not done a magneto check when climbing out.  I do airborne mag checks in cruise (not with this issue) but have not done one while climbing out.  The exhaust was removed when the cylinders were done so hopefully there is no blockage there.  It is just a head scratcher that it has happened on multiple cylinders.  I know you should not assume anything but I would hope that any intake leak would have been taken care of when the new cylinder was put on or any blockage in the exhaust would have been cleared between cylinder changes.  The only thing that was not done of course was any mag changes or harness changes.  So maybe it could be a mag issue since it has happened with two cylinders.  Thanks for the advice.

By the way, what could cause detonation on two new cylinders in the #3 position?  Since it happened to the previous cylinder as well.

[Ragsf15e]

I wouldn’t think an induction leak would make such a significant impact at full power.  The intake is fully open anyway, no?  Im sure it could have some increased air as it doesn’t need to go through the filter, tubes, etc, but this much?

[N201MKTurbo]

49 minutes ago, Greg Ellis said:

I have not.  I will try that.  I have the instructions on how to do it.  Thanks.  Other than a possible intake leak what would other causes to a lean cylinder in a carbureted engine?

Let’s do the test and if it shows a problem, then we will try to figure out what is wrong.

[Greg Ellis]

20 minutes ago, N201MKTurbo said:

Let’s do the test and if it shows a problem, then we will try to figure out what is wrong.

I will try to get out there this weekend and do the tests.  Thanks.

[47U]

6 hours ago, Greg Ellis said:

The new cylinder was running very hot on the EDM 900.

Random thoughts…

The ‘63C has adjustable cowl flaps.  Check to make sure they’re opening to spec, and I wouldn’t be against adjusting them to be open another 1/2 or 3/4 inches.

The EDB 900 ring probe vs. bayonet probe… Since the 900 is primary, when you substituted the ring probe on #3 was it installed underneath the bayonet fitting that the factory CHT probe used?  My E.I. UBG (not primary) documentation says to wrap some fire sleeve around the ring probe installed underneath the bayonet fitting.  Otherwise the CHT reading for that cylinder will read low.  On mine, the fire sleeve raised the #3 CHT some 30-40 degrees and now #3 reads right inline with the other three cylinders using screw-in CHT probes.

Mags, ignition leads, and plugs were already mentioned…

What’s the takeoff fuel flow?  Fuel flow should affect all the cylinders CHT, but if it’s low and you improve it to 17-18 gph and it brings down all the cylinders CHT, that’d be an improvement for #3 (admittedly not explaining yet why #3 is CHT is higher that the others).

Powerflow exhaust?  

Target airspeed on climb?  Accelerating to 120 helps my CHTs stay just under 400 on a hot day.

The cold air intake to the muffler shroud is on the rear baffle aft of #3 cylinder.  Is that duct in good condition?  Muffler shroud fits tight?  Carb heat flapper closes tight (bearings not worn).  Excess air flow to the muffler shroud might siphon cooling air that otherwise would be available for #3 cooling fins.

What did the cam lobes look like when the cylinders were off?  I think the #3 exhaust valve doesn’t share a cam lobe, but the #3 intake valve does share the cam lobe with the #4 cylinder.  I’m not sure if there’s any relevancy there…. like I said, random thoughts.

Is it possible that there was a manufacturing issue with the #3.  Undersized bore, improper ring gaps… something else?  You’d have to pull the cylinder to find out, which would be pretty drastic… if you’re going that far into the weeds, swap #1 and #3 cylinders and see what happens.

 

[Fritz1]

Trace the ignition leads make sure both mags are wired correctly, the spark plug nuts say where they should go, but the markings may be wrong

[Greg Ellis]

21 minutes ago, 47U said:

Random thoughts…

The ‘63C has adjustable cowl flaps.  Check to make sure they’re opening to spec, and I wouldn’t be against adjusting them to be open another 1/2 or 3/4 inches.

The EDB 900 ring probe vs. bayonet probe… Since the 900 is primary, when you substituted the ring probe on #3 was it installed underneath the bayonet fitting that the factory CHT probe used?  My E.I. UBG (not primary) documentation says to wrap some fire sleeve around the ring probe installed underneath the bayonet fitting.  Otherwise the CHT reading for that cylinder will read low.  On mine, the fire sleeve raised the #3 CHT some 30-40 degrees and now #3 reads right inline with the other three cylinders using screw-in CHT probes.

Mags, ignition leads, and plugs were already mentioned…

What’s the takeoff fuel flow?  Fuel flow should affect all the cylinders CHT, but if it’s low and you improve it to 17-18 gph and it brings down all the cylinders CHT, that’d be an improvement for #3 (admittedly not explaining yet why #3 is CHT is higher that the others).

Powerflow exhaust?  

Target airspeed on climb?  Accelerating to 120 helps my CHTs stay just under 400 on a hot day.

The cold air intake to the muffler shroud is on the rear baffle aft of #3 cylinder.  Is that duct in good condition?  Muffler shroud fits tight?  Carb heat flapper closes tight (bearings not worn).  Excess air flow to the muffler shroud might siphon cooling air that otherwise would be available for #3 cooling fins.

What did the cam lobes look like when the cylinders were off?  I think the #3 exhaust valve doesn’t share a cam lobe, but the #3 intake valve doesn’t share the cam lobe with the #4 cylinder.  I’m not sure if there’s any relevancy there…. like I said, random thoughts.

Is it possible that there was a manufacturing issue with the #3.  Undersized bore, improper ring gaps… something else?  You’d have to pull the cylinder to find out, which would be pretty drastic… if you’re going that far into the weeds, swap #1 and #3 cylinders and see what happens.

 

Cowl flaps are the correct adjustment.  The ring probe was installed underneath the bayonet fitting so it would hold it in place.  There was fire sleeve around the wiring but I don't think right up to the ring itself.

Take off fuel flow is 19 gph (I installed the richer carb a long time ago). 

No Powerflow exhaust just stock exhaust which was rebuilt about 5 or 6 years ago.

Carb heat box was rebuilt 2 annuals ago.  All ducting looks in good shape.

Not sure about the Cam lobes when the cylinder was off.

If there was a manufacturing issue with the #3 cylinder then it would have been with 2 in a row because the cylinder before this one had the same issue that was possibly masked by the ring probe.

Thanks for all the ideas though.  It helps tremendously.

[Greg Ellis]

12 minutes ago, Fritz1 said:

Trace the ignition leads make sure both mags are wired correctly, the spark plug nuts say where they should go, but the markings may be wrong

I will check on this on the weekend.  Thank you.

[hammdo]

Greg, do you have the factory dog house? If you want a fellow C-driver to observe while you fly, I can come by…

-Don

[Ragsf15e]

30 minutes ago, Greg Ellis said:

I will check on this on the weekend.  Thank you.

I hesitate to ask this for fear of sounding stupid, but you’ve changed plugs, right?  There’s nothing on the plugs in that cylinder that could cause pre ignition?  I have a hard time believing that you wouldn’t see it on runup, but? Im sure this was likely done and all, but it’s heating up so fast it just seems like detonation/pre ignition.

[Greg Ellis]

14 minutes ago, Ragsf15e said:

I hesitate to ask this for fear of sounding stupid, but you’ve changed plugs, right?  There’s nothing on the plugs in that cylinder that could cause pre ignition?  I have a hard time believing that you wouldn’t see it on runup, but? Im sure this was likely done and all, but it’s heating up so fast it just seems like detonation/pre ignition.

I have not changed the plugs yet but my mechanic said that I could try that and see what happens.  The plugs are the same from the first cylinder to this one and both had the issue.  So the I was going to change the plugs this weekend since it is something an owner can do and I can get it done before the mechanic is able to get the airplane in.  Thanks for the advice.

[Greg Ellis]

43 minutes ago, hammdo said:

Greg, do you have the factory dog house? If you want a fellow C-driver to observe while you fly, I can come by…

-Don

I replaced the doghouse quite some time ago with a new one made by Airforms Alaska which apparently is now owned by McFarlane.  They no longer make them for the C model and start at the J model.  It is still the doghouse but not the original.  I may have gotten the last one they made and then they stopped making them.  It was made quite well (powder coated and all) and has held up well.

Thank you for the observation offer and I will let you know.

[Andy95W]

The ring-type probe is not very accurate compared to the actual probe that goes into the hole on the cylinder head.  They generally read 40-50° lower than the other probes.  For safety, I definitely would not run your #3 cylinder with the ring type probe.  @47U mentioned the fire sleeve, I hadn’t heard about that and will have to try it on mine.

The “intercylinder baffles” that someone mentioned isn’t a part of the doghouse, it’s the small piece of sheet metal that extends between the underside of cylinders #1 and #3 (as well as between 2 and 4 on the other side of the engine).  Yours are probably there, but it would be worth a look to make sure it’s fitted properly.

There is an area behind and below cylinder #3 in the vicinity of the oil pressure adjustment that can be closed up a lot using some scrap sheet metal.  The doghouse is very lacking in that area.

Swapping spark plugs is quick and easy and would be my first priority.

As others have mentioned, about the only thing that could cause an excessively lean mixture on only one cylinder in our carbureted engines would be an induction air leak, but that would show as an extremely high EGT for #3.  Checking that would be my second priority, as well as checking as much of the rest of #3’s intake manifold while you’re at it.  Also checking valve lash, in case the pushrods got mixed up.

I didn’t know there was a way to check the mixture distribution in a carbureted engine, could you please post that?

Good luck, please keep us posted about what you find out.

[Greg Ellis]

12 minutes ago, Andy95W said:

The ring-type probe is not very accurate compared to the actual probe that goes into the hole on the cylinder head.  They generally read 40-50° lower than the other probes.  For safety, I definitely would not run your #3 cylinder with the ring type probe.  @47U mentioned the fire sleeve, I hadn’t heard about that and will have to try it on mine.

The “intercylinder baffles” that someone mentioned isn’t a part of the doghouse, it’s the small piece of sheet metal that extends between the underside of cylinders #1 and #3 (as well as between 2 and 4 on the other side of the engine).  Yours are probably there, but it would be worth a look to make sure it’s fitted properly.

There is an area behind and below cylinder #3 in the vicinity of the oil pressure adjustment that can be closed up a lot using some scrap sheet metal.  The doghouse is very lacking in that area.

Swapping spark plugs is quick and easy and would be my first priority.

As others have mentioned, about the only thing that could cause an excessively lean mixture on only one cylinder in our carbureted engines would be an induction air leak, but that would show as an extremely high EGT for #3.  Checking that would be my second priority, as well as checking as much of the rest of #3’s intake manifold while you’re at it.  Also checking valve lash, in case the pushrods got mixed up.

I didn’t know there was a way to check the mixture distribution in a carbureted engine, could you please post that?

Good luck, please keep us posted about what you find out.

Thank you for your post.  The intercylinder baffles are there.  I saw them with the S shaped hook coming up between the #1 and #3 cylinder hooking on the top holding them in place.

I will check the area you mention by the oil pressure adjustment to see if there is much of an opening there.  The mixture distribution was offered up by @N201MKTurbo.  Mentioned doing the GAMI test even though it is carbureted and not fuel injected to help see if the cylinder is running lean.  Mike Busch also has instructions on how to check if a cylinder is running lean by the manifold pressure so I am going to try that as well.

But first is to put in new spark plugs and see what happens.

Thanks again.

[Bartman]

2 hours ago, Fritz1 said:

Trace the ignition leads make sure both mags are wired correctly, the spark plug nuts say where they should go, but the markings may be wrong

This does happen. In fact, I ordered a new harness and two of the leads were labeled wrong. 

[47U]

2 hours ago, Andy95W said:

For safety, I definitely would not run your #3 cylinder with the ring type probe.

@Greg Ellis  since the EDM 900 is primary, what Andy says is good advice.  

Andy’s mention of the inter-cylinder baffles (make sure they’re installed on all the way back to the base of the cylinder) made me think of something else baffle related… the baffle tie rods, two under each bank of cylinders.  You can see the tie rod in the pic of a friends D/C model with the fire sleeve around the ring probe.  He didn’t think the fire sleeve made that much difference in the CHT reading.

I did my fire sleeve around both probe’s harnesses… and had better readings, I think.  The zip ties got brittle with the heat and I replaced them safety wire.  Still, even with fire sleeve, the ring probe is not as accurate as a screw-in probe, for sure.

[Greg Ellis]

5 minutes ago, 47U said:

@Greg Ellis  since the EDM 900 is primary, what Andy says is good advice.  

Andy’s mention of the inter-cylinder baffles (make sure they’re installed on all the way back to the base of the cylinder) made me think of something else baffle related… the baffle tie rods, two under each bank of cylinders.  You can see the tie rod in the pic of a friends D/C model with the fire sleeve around the ring probe.  He didn’t think the fire sleeve made that much difference in the CHT reading.

I did my fire sleeve around both probe’s harnesses… and had better readings, I think.  The zip ties got brittle with the heat and I replaced them safety wire.  Still, even with fire sleeve, the ring probe is not as accurate as a screw-in probe, for sure.

Thanks for the photos.  The baffle tie rods are all attached.  Two on each side. I checked that last weekend.  The inter cylinder baffles are there as well.  I will check their actual positioning this weekend to verify they are correct.

[Shadrach]

40 minutes ago, Andy95W said:

The ring-type probe is not very accurate compared to the actual probe that goes into the hole on the cylinder head.  They generally read 40-50° lower than the other probes.  For safety, I definitely would not run your #3 cylinder with the ring type probe.  @47U mentioned the fire sleeve, I hadn’t heard about that and will have to try it on mine.

 

I have recently started flying a 63C and it runs while it runs hotter than My F model, it runs runs very reasonable in cruise.  I lean for the setting that yields the most even CHTs

 

16 hours ago, 47U said:

I did my fire sleeve around both probe’s harnesses… and had better readings, I think.  The zip ties got brittle with the heat and I replaced them safety wire.  Still, even with fire sleeve, the ring probe is not as accurate as a screw-in probe, for sure.

The above probe is installed I/A/W the manufacturer's instructions.  When properly installed, the piggy back probe will still read lower than the bayonet probe but in my experience the delta is 10% or less. Without the fire sleeve correctly installed, I suspect the delta in temperature readings is much larger.

[Greg Ellis]

So, with the bayonet probe as I have mentioned the cylinder runs upwards to 480 on take off and drops down to 430 or so in cruise while the other three cylinders barely reach 400 if that on take off and run in the mid 300's in cruise.  When I had the ring probe on the #3 cylinder would run in the lower to mid 300's all the time, never getting close to 400 even with a new cylinder that was not broken in yet.  So the ring probe is not only registering lower than the other cylinders it is registering over 100 degrees lower than the bayonet probe in the same cylinder.