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Franklin 165 CHT

Joe Reheiser
(@jmreheiser)
Active Member

Hi everyone -

My Stinson 108-3 (Franklin 165hp) does not have a Cylinder Head Temp gauge.  However, a friend's does and he asked me if I knew what the in flight CHT should be.  I couldn't answer him, so I'm asking the Stinson and Franklin experts on this forum, does anyone know what kind of CHT you should expect to see on a 30 degree day?  The Franklin engine manual shows 530 as the maximum, but the range you should see in flight is not addressed.  Any help or advice would be greatly appreciated.

Thanks,

Joe Reheiser

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Topic starter Posted : 18/01/2022 2:23 am
Luke Peterson
Active Member

@jmreheiser Hey Joe, depends on which cylinder it's on. I run a 6 cht/egt engine monitor on my 165 with well type probes, where the maximum temperature is limited at 445°F. I run air blockers on my grilles like the Cessna 170's for the winter being in MN. At 30° with the blockers in I'll see my highest temp at 300° and my lowest about 220°. Even in the summer on an 80° day I haven't seen above 330°. They run unusually cool it seems and I'd like to see them warmer especially in the winter. Single digit days I'll barely break 200° on my front cylinders with the blockers. 

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Posted : 19/01/2022 12:44 am
Joe Reheiser
(@jmreheiser)
Active Member

Hi Luke -

 

Thanks for the quick response.  Sincerely appreciate it.

 

All the best,

 

Joe Reheiser

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Topic starter Posted : 19/01/2022 7:47 pm
Luke Peterson
Active Member

@jmreheiser no problem. As long as your baffling is in good shape, getting hot shouldn't be an issue in the cold. It is nice information to have though. 

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Posted : 20/01/2022 2:50 pm
Dennis Crenshaw
Reputable Member

@ljhpete Hi Luke.  Is there one of the cylinders that runs consistently hotter than the others?

 

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Posted : 03/02/2022 9:01 pm
Luke Peterson
Active Member

@dcn6102m Hi Dennis, yes my #1 cylinder always runs the warmest by 25-50°. Anywhere from 275-305° is what I see. I've been trying to bring that more in line with the rest of the cylinders and haven't come up with a solution yet. I've added silicone material to seal the top baffling up better. #2 has got a gaping hole around the dip stick so the air might rush over there, because it runs fairly cool. 

I don't have enough other engine and Stinson data to determine if that's just how mine runs or not. 

I know on the Stinson service bulletin 269, which is the 180 horse Franklin install on the -3, it says to put cylinder head temp bulb and adapter in the top of #1. So maybe that's the cylinder that runs warmer? I don't really know, but I'd like to. 

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Posted : 03/02/2022 9:37 pm
Dennis Crenshaw
Reputable Member

@ljhpete Thanks Luke.  That was my guess, either #1 or #4.  How about EGT?  Does any cylinder tend to be leaner than the others? 

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Posted : 03/02/2022 10:06 pm
Luke Peterson
Active Member

@dcn6102m If I remember right, my #4 leans out first. I just run a little carb heat and 2550-2600 and flip it to normalized mode on the engine monitor. Levels everything out and just shows if there's a drastic change. I don't have enough data on others to know if #4 gets lean first is common either. 

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Posted : 03/02/2022 11:22 pm
Dennis Crenshaw
Reputable Member

@ljhpete  Thanks Luke.  I don't know if I would ever spring for a complete engine analyzer, but maybe a single CHT and single EGT probe if I knew which cylinders.  I think others have said #1 was their hottest CHT, so that's probably a safe bet.  Leanest cylinder might be a little harder to pin down.

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Posted : 05/02/2022 12:39 am
Luke Peterson
Active Member

@dcn6102m the engine analyzer is nice to see trends since the data is recorded and quickly recognizing problems. In my experience the EI egt probes that came in my kit are a bit temperamental. They have some heavy duty probes they use on turbocharged engines that are better I guess. It's nice to have it on an unknown engine, but after having it a few years I don't pay attention to it much. 
I agree, I think there are too many variables to track down the leanest cylinder. Mostly the casting anyway. 

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Posted : 13/02/2022 11:31 pm
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