CHT changes after placement change
Posted: Tue Mar 29, 2016 11:18 pmDue to a quiet board here - I'm going to update you on several recent Jab3300 (in my Waiex) findings after an extensive annual condition inspection at 178 hours total time:
Item 1: I had to yank my heads due to very early and severe wear on #1 exhaust valve guide and pushrod(ground off about 1/3 of tip). #3 was also prematurely wearing - but not nearly as bad. Lots of baked on and crusted oil on the #1 rocker arm. So - I yanked all my heads off, sent #1 & #3 heads in to Pete K for new guides and exhaust valves, and disassembled/inspected/walnut blasted all the others. I also removed, cleaned and lapped in all valves/seats and lapped the heads onto the cylinders, and upgraded to hollow pushrod/rocker arm and quicker bleed lifters. Pretty easy to do all this! First time for me into this engine -but I do have experience on other types, so not too intimidating. I did have oil weeping and staining the heads/cylinders on five of the 6 cylinders as well.
Item 2: One of the things I did when the heads were off, was to change the CHT pickups from the head bolt(nearest exhaust valve) per Sonex suggestion to the crown between the spark plugs per Jabiru suggestion. Interesting CHT results after several flights- I went from #1 CHT always being the absolute coldest reported (ave 265f during flight) to being the absolute hottest reported (ave 335f during flight). The ave temp change was HUGE - 70 bloody degrees F. Keep in mind that the pick up is right at the inlet opening per Sonex setup. Cylinder #3 went up as well - but not nearly as dramatically (only about 30f ave). I confirmed with a CHT swap with #3. This just may possibly play into the early demise of the #1 and #3 cylinder exhaust valve guides and solid pushrods (early hydraulic engine) - but I'm not going to completely chalk it up to that.
Item 3: A change in reported oil pressures at idle after converting the engine when engine is fully heat soaked. Engine oil pressure during idle previously was around 55psi, now is now 39psi. I'm guessing - that it has to do with the fluid flow dynamics of the different components. Nothing the wrong with this - just an interesting side note.
Item 4: Original plugs/rotors and caps were still in and had checked okay at 120 condition inspection. They were absolutely end of life at this point. Still ran okay - but end of life due to corrosion and wear. In future - changes of all these components will be at 150 hours for me.
Item 5: I modified my intake baffles to hinge them like Jeff Schultz did. Absolutely best move I ever made!! Wish I would have done this at the beginning. Super simple to yank the piano hing pin on top of the baffle and have the side fold down. Makes inspection much easier. Baffle is same size, shape - the side just hinges down now.
Item 6: Consulted with both Pete at JabUSA, and Camit rep in Kansas City. Both bent over backwards to get info and parts back to me right away and help out. We've got a fantastic dealer support network in the USA!!
Lorin
N81YX
Happily using a freshly installed electric flap setup compliments of surgery on left wrist...
Item 1: I had to yank my heads due to very early and severe wear on #1 exhaust valve guide and pushrod(ground off about 1/3 of tip). #3 was also prematurely wearing - but not nearly as bad. Lots of baked on and crusted oil on the #1 rocker arm. So - I yanked all my heads off, sent #1 & #3 heads in to Pete K for new guides and exhaust valves, and disassembled/inspected/walnut blasted all the others. I also removed, cleaned and lapped in all valves/seats and lapped the heads onto the cylinders, and upgraded to hollow pushrod/rocker arm and quicker bleed lifters. Pretty easy to do all this! First time for me into this engine -but I do have experience on other types, so not too intimidating. I did have oil weeping and staining the heads/cylinders on five of the 6 cylinders as well.
Item 2: One of the things I did when the heads were off, was to change the CHT pickups from the head bolt(nearest exhaust valve) per Sonex suggestion to the crown between the spark plugs per Jabiru suggestion. Interesting CHT results after several flights- I went from #1 CHT always being the absolute coldest reported (ave 265f during flight) to being the absolute hottest reported (ave 335f during flight). The ave temp change was HUGE - 70 bloody degrees F. Keep in mind that the pick up is right at the inlet opening per Sonex setup. Cylinder #3 went up as well - but not nearly as dramatically (only about 30f ave). I confirmed with a CHT swap with #3. This just may possibly play into the early demise of the #1 and #3 cylinder exhaust valve guides and solid pushrods (early hydraulic engine) - but I'm not going to completely chalk it up to that.
Item 3: A change in reported oil pressures at idle after converting the engine when engine is fully heat soaked. Engine oil pressure during idle previously was around 55psi, now is now 39psi. I'm guessing - that it has to do with the fluid flow dynamics of the different components. Nothing the wrong with this - just an interesting side note.
Item 4: Original plugs/rotors and caps were still in and had checked okay at 120 condition inspection. They were absolutely end of life at this point. Still ran okay - but end of life due to corrosion and wear. In future - changes of all these components will be at 150 hours for me.
Item 5: I modified my intake baffles to hinge them like Jeff Schultz did. Absolutely best move I ever made!! Wish I would have done this at the beginning. Super simple to yank the piano hing pin on top of the baffle and have the side fold down. Makes inspection much easier. Baffle is same size, shape - the side just hinges down now.
Item 6: Consulted with both Pete at JabUSA, and Camit rep in Kansas City. Both bent over backwards to get info and parts back to me right away and help out. We've got a fantastic dealer support network in the USA!!
Lorin
N81YX
Happily using a freshly installed electric flap setup compliments of surgery on left wrist...
