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Went to our Aussie Natfly and went to a forum put on by Rod Stiff and Jabiru about their latest developments and the Service Bulletins.
you need to check the serial number of your engine and the hours flown before you do anything.. Then reread the SB.. on some engines you have to do just the nuts, others the through bolts as well.
These bolts have been a problem for a quite awhile....
I had one break in my early hours of training... (about a year ago)....
Engine started running rough.. then a big vibration.
had to idle the engine and glide back to the strip.... (not too far away)...Also cracked a cylinder as well....
I think it's due to harmonics....
Had another problem (in a different plane) Dropped a valve on start up.... I believe that was the valve seat coming lose due to cooling shock..... I think that was the verdict....
Don't know if I would ever install a jab.....
Out of interest, was this engine hydraulic lifter , also which valve ,ex. or inlet?.
The pistons in these engines are in the WRONG WAY ROUND!. We have reversed the pistons in a number of engines with amazing results such as dramatic reduction of vibration, quieter , more power, less fuel consumption, engines run cooler by 50deg f on average. I believe the pistons in the wrong way are the main contributing factor to the bolt failure's , high c/rod brg and main brg wear, due to excessive loading.
pistons in the wrong way ,give similar effects as detonation , in fact I have seen a number of stripped engines , and could not find any signs of detonation, this includes testing the hardness of the piston ,head.
With regard to nut replacement . this should be done with caution ,as these crank case halves almost always fret , retightening these bolts will cause halves to pull together and reduce m/brg clearance. [ another time bomb] even if engine appears to turn over ok ,it does not indicate that the brgs have not got a reduced clearance, which could lead to a seizure or partial seizure some time down the track . When we change piston's and fit bolts we don't use Loctite on the threads , this enables the bolts to be torqued[checked [ during regular service, so far they remain tight after more than 400 hrs .
Adrian Dines Automotive Engineer firstname.lastname@example.org
Update 6/16: Completed all but 4 of bottom nuts in 6 hours. Maybe I'm just slow. Had to remove both intake and exhaust manifold pipes, carby spider and fuel pump. This made nut replacement easier instead of impossible but not pleasant. The most aft nut on #6 cylinder will require a special wrench I believe. I've tried to find a 7/16 cylinder base wrench but to no avail. Found several 1/2 and above, no 7/16. I think this would solve the problem. May have to make one. More on that later.
Did discover several intake and exhaust manifold allen head machine screws loose. Not sure why. By loose I mean just snug enough to require a slight pull on the allen wrench to start the removal. Not sure of the torque figure during installation or if Locktite is required. Need to research that for installation. The intake screws have a lock washer, the exhaust don't. Gaskets on the intake none on the exhaust. I have 30 hours on the engine.
It's still a BEAR. I expect at least one more day. That will be about 3 days on the nut replacement. I have a good A&P friend on the job too. We've been slow and methodical and have had to improvise at times and have learned a lot. The next engine would be easier, maybe just a small bear.
You'll need a 7/16 x 3/8 12 point torque adapter tool. Snap-On has the tool. It works on the torque wrench as well as a ratchet to help take off the old nuts. http://buy1.snapon.com/catalog/item.asp?item_ID=2213&group_ID=268. I was lucky, a local A&P loaned me the tool. You'll need a long 1/4" allen wrench 6"s at least. Also two 6" - 8" 7/16" 12 point box wrenches. You'll also need two nuts to act as lock nuts for the through bolts. I wouldn't use the steel nuts you take off the bolts. The shoulder on the steel nut gets in the way when you try to hold the first nut you add. You'll probably need someone to hold the lock nuts to keep them from turning as you remove the nut on the other end of the bolt.
The service bulletin states that it has not been mandated by any airworthiness authority. It also states that while numbered as a "Service Bulletin", it is to be considered equivalent to a "Safety Direction" (interesting word. Should probably 'directive'; still the intent is clear).
In the United States, for S-LSA aircraft, manufacturers "Safety Directives" are mandatory. For EAB, or E-LSA, they are not.
That's the legal perspective. From a safety point of view, it is prudent to comply.