ccsmith51
Well Known Member
Y'all might remember that I have been chasing a hot start issue on my O-360-A1A RV-6. I replaced the MA4-5 carb with an overhauled one, thought that solved the problem, but it did not.
Then I took the Slick mags and had them serviced. They were in rough shape with about 800 hours on them. After new points, point cams, bearings, seals, etc. they are like new.
I had my A&P install and time them. He has all the neat gizmos for timing, like the proper pins, the laser thingy that he attached to the starter gear at the timing mark, and the gold box that beeps when the mags are in the right spot.
We put them in and she started great. I have flown at least a half-dozen flights and the engine seems to run better, there is definitely much less RPM drop on run-up.
I have not flown long enough on one flight, and it has not been hot enough to get the engine really heat soaked, so I don't know if the hot start issue is resolved...
But, that is not my new situation. Since I reinstalled the overhauled mags my CHT has increased about 150?! It doesn't seem to matter what I do, it still reads about 150? higher than before. Where it used to read about 250? during climb-out it now reads 400?. That is either at WOT and 2700 RPM and full rich and 100 MPH, or climb cruise at 24" and 2400 RPM and 110 MPH.
The original probe was a ring type under the #4 spark plug. Today I replaced that with a new bayonet probe, which I am told is more reliable and accurate than the ring type.
There was no change in the CHT reading.
So, I have some questions:
1) If all I did was overhaul the mags, how could that affect CHT?
2) Is 400? on #4 too high?
3) What could have caused the CHT to increase by about 150? if all other parameters are the same?
I asked my A&P if the timing could be off. He said he doubted it because it starts so good. He said that next time I pull the cowl he will check it again, and he suggested I move the probe to #2 cylinder and see what the readings are.
Any thoughts, ideas, or suggestions would be appreciated.
Thanks!!
Then I took the Slick mags and had them serviced. They were in rough shape with about 800 hours on them. After new points, point cams, bearings, seals, etc. they are like new.
I had my A&P install and time them. He has all the neat gizmos for timing, like the proper pins, the laser thingy that he attached to the starter gear at the timing mark, and the gold box that beeps when the mags are in the right spot.
We put them in and she started great. I have flown at least a half-dozen flights and the engine seems to run better, there is definitely much less RPM drop on run-up.
I have not flown long enough on one flight, and it has not been hot enough to get the engine really heat soaked, so I don't know if the hot start issue is resolved...
But, that is not my new situation. Since I reinstalled the overhauled mags my CHT has increased about 150?! It doesn't seem to matter what I do, it still reads about 150? higher than before. Where it used to read about 250? during climb-out it now reads 400?. That is either at WOT and 2700 RPM and full rich and 100 MPH, or climb cruise at 24" and 2400 RPM and 110 MPH.
The original probe was a ring type under the #4 spark plug. Today I replaced that with a new bayonet probe, which I am told is more reliable and accurate than the ring type.
There was no change in the CHT reading.
So, I have some questions:
1) If all I did was overhaul the mags, how could that affect CHT?
2) Is 400? on #4 too high?
3) What could have caused the CHT to increase by about 150? if all other parameters are the same?
I asked my A&P if the timing could be off. He said he doubted it because it starts so good. He said that next time I pull the cowl he will check it again, and he suggested I move the probe to #2 cylinder and see what the readings are.
Any thoughts, ideas, or suggestions would be appreciated.
Thanks!!