I will start this blog entry by revealing the ending. My Zodiac XL is happily flying again powered by its smooth-running powerful Jabiru 3300 engine. Saturday I flew 126 miles with the overhauled engine.

Now back to the beginning…

My Jabiru 3300 engine is serial number 1,256. It is about three years old and has 600 hours on it. Since it was manufactured several improvements have been introduced by Jabiru to address high oil temperatures in the cylinders. They are:

1) The oil cooler size has been increased by 50%
2) The fiberglass air ducts have been made wider and now cool substantially more of the cylinders
3) A defect in the cylinder base and through-bolt nuts has been revealed which affects some engines. The defect distorts the cylinder and allows blowby resulting in hot exhaust gas heating the oil
4) The recommended oil has been changed from Aeroshell 100 to Aeroshell 15W 50. The newly recommended oil is 50% synthetic and is better able to withstand high temperatures
5) The pistons have been changed so that the ring grooves are wider. This reduces the chance of the rings sticking in there grooves.

Now you may say “I don’t have high oil temperature”. I would say “how do you know”? Your oil temperature gauge tells you the temperature of the oil in the pan, not the temperature of the oil on the piston rings. If engine oil is exposed to temperatures above about 450 degrees the oil will change into a tar-like substance. These high temperatures can be found in the cylinders where all the heat comes from.

I am no expert on oil and oil temperatures. What I can tell you is my stock Jabiru 3300 engine required an expensive early engine overhaul because the piston rings had become stuck in the piston ring grooves which resulted in reduced performance and excessive oil consumption. So if your Jabiru engine lacks the above improvements you might want to look into some modifications before you encounter a similar fate.

I replaced the pistons, rings, cylinders and rod bearings. I had the heads and valves reworked. Essentially this is the 1000 hour top-end being done at 600 hours.

So what do the engine parts cost? Here is a picture of my parts invoice.

I did all the disassembly and reasonably myself with the aid of the Jabiru manual and an occasional phone call to Jabiru Pacific. I took a few pictures along the way.

The following picture shows a piston without rings, a wristpin and connecting rod. Notice the wristpin end of the rod is discolored. That is from the heat of machining to the larger diameter needed for the new piston's larger wristpin.

The next picture shows the dot on the scraper ring. The scraper ring is the second one down from the "top" of the piston. The dot goes up. The top ring does not have a dot nor an up or down.

The next picture shows the three-piece oil-control ring which goes in the wide bottom groove. This is a sandwich with the bronze-colored ring in the center.

Here you can see the cylinder and the head. There is no head gasket. That is why it is important to keep the 6 head bolts correctly torqued.

Here is a view "down" the cylinder to the head.

I chose to install the rings on the pistons, connect the rods to the pistons, insert the pistons into the cylinders and insert the rod bearings into the connecting rods all in the comfort of my office at home. There are a number of tricky steps here. Keeping the parts correctly oriented and labeled will help. The pistons have a forward and backward relative to the front of the engine. They have markings for this. Half of them end up "right-side up" and half end up "upside down". The rings need to be oriented correctly relative the the top of the engine. The instructions that came with the rings are marginal. I made numerous internet queries for additional information. Here is a picture of all 6 finished assemblies.

Next I took the assembled parts out to the hanger and started several days work putting things back together. I installed the cylinders in order starting with #1 and working back to #6. Here is a pilot's side view of the engine with the number 2 cylinder in place.

It was a bit of a trick to get the connecting rods back in place on the crankshaft. In the next three pictures you can see how I did it. I oiled the rod bearings to help them stay in place. I also used safety wire to keep the cap from sliding out of place and falling down into the motor. Screw this up and you get to take the oil pan off.

Here you can see the safety wire holding the cap so it does not slip into the abyss.

Next I used a long head bolt, which happens to be the same diameter and thread as the connecting rod bolts, to mate the rod to the cap. Once the rod and cap are mated, you can remove the safety wire, screw in the top rod bolt then replace the long head bolt with the rod bolt and torque them both both.

The Jabiru manual indicates that the rod bolts be primed with loctite 7471 primer and "glued" in with Loctite 620. Expect to pay about $20 for each of these. I ordered them off the internet because I could not find these items locally.

Here is a picture of the ends of the push rods. Notice the scoring on the ends. (The three on the right are normal looking.) This is a sign of oil starvation - a design flaw which Jabiru will soon be addressing with yet another modification.

The next picture shows the worn out and damaged motor mount rubber (lower on pilot's side). Its close to metal on metal. In 600 hours and two years the engine had sagged about 3/8 of an inch. This was affecting engine pitch and clearance around the oil cooler.

I bought much stronger rubbers from here.

If I were writing a manual there would be many more steps and pictures here. But because I was working alone, stopping to take pictures with oily hands did not seem to happen - sorry. There were a few challenges like getting the two nuts, one on each end of the through-bolts, to end up in the right place - arrrgggg..

Skipping ahead a few days and a few busted knuckles, its time to do the ground run-in of the engine. Two identical 46.5 minute run-in sequences are spelled out in the Jabiru manual. There are specific RPMs to be held for a specified number of minutes. I built a spreadsheet to make following this sequence easier. I used a stopwatch to stay on-track.

The manual forbids doing this with the standard cooling ducts. Far more cooling is needed to prevent over-temps. Here is a picture of the shroud I made from a sheet of galvanized steel. Notice the band of aluminum for a bit of extra insurance. I did not want this chunk of metal to go flying!

The above shroud worked quite well but I was not able to run the three-minute high-RPM segments without inserting a one minute cool down period.

The engine fired up right away. It seemed a bit rough and the #5 cylinder was too cold. I shut it down and started to investigate. The sparkplug wires were OK so it had to be compression - dang! I pulled the valve cover on #5, rotated the prop and watched the rocker arms. At the top of the compression stroke I checked for clearance. There was the problem; no play in one of the rocker arms. The tappet end of the push rod was not properly seated in the center of the tappet so the valve could not close all the way. Sloppy mistake! A little tweaking with a screw driver and she is all fixed. That was easy...

After the run-in I finish by putting the standard air ducts and the cowling back on. Too late to fly it today.

Next day, after the morning fog cleared, it was time for the first flight. I told the tower I had a newly overhauled engine and wanted to climb in a circle over the airport. They kindly agreed. Of course the engine ran hot just like I expected. After one minute of full throttle climb I pulled back to 2300 RPM and continued a slow climb up out of the KSTS airspace. At 3,000 feet with the engine working well I said goodbye to the tower and head off to the QSP open house in Cloverdale a happy camper as they say...


P.S. You can read additional information in my prior blog post.


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Comment by Mark Ertz on March 24, 2013 at 8:51am


Am doing top overhaul.  also putting on Retoc TBI40s. I want primer and mixture control.  What is your current a/c status?

Comment by Phill Barnes on October 16, 2009 at 5:05pm
Hi Guys
Do you think it might be a good idea to have a "Jabiru Tips & Tech" blog to keep all info organised and easy to find?

Comment by Stephen R. Smith on October 16, 2009 at 3:13pm
If only a person could actually make a living that way...
Comment by Bob Simmons on October 16, 2009 at 3:09pm
Steve, maybe you should start your own Jabiru tech support site.
Comment by Stephen R. Smith on October 16, 2009 at 12:24pm
Hello Steve,

There is a large o-ring which seals the cylinder to the block so its not just a machine fit. I doubt very much that re-torquing the nuts at the base of the cylinder will reduce the oil seepage. If the tamper-evident paint does not show movement in the nuts I would not expect them to need any adjustment. The torque is in the book (15 ft lb then 30 ft lb two stages) but good luck getting a torque wrench on them. You can, but its hard to do.

I don't think this seepage is a sign of over-filling. If you take out the dipstick and re-position it beside the tube that it normally lives in you will see that the normal fill levels are an inch or so down from the top of the pan. The bottom of the cylinders are a good distance above the pan. I think the seepage is from the oil being flung off the rod bearings. Your going to have to get used to it.

At 600 hours my engine was "weeping" oil from many places. Just enough to make a mess and look "bad" but not actually very much in terms of total volume.

Be sure to check the bolts on the fuel pump. Mine were almost finger loose at my first annual. Locktite would be a good thing on those two bolts.

Comment by Stephen R. Smith on October 15, 2009 at 3:04pm

I only have 126 miles on the overhauled engine so I don't have a lot of data for you. The highest temp I saw was 207. It was about 68 degrees on the OAT. The engine is breaking in so its hot anyway. First reaction is yes quite a bit cooler but as I say, I need to collect more data before I am comfortable putting claims out there.

Comment by Stephen R. Smith on October 15, 2009 at 11:40am

The new cooler is the same width but twice as long. The overall design and mounting points on the new cooler are exactly the same as the old; the cooler just has twice as many rows. The new cooler has the same oil line fittings as the old.

I was able to use the original mounting bracket however I added some light-weight angle stock to extend the reach to the bottom of the cooler. The angle stock was placed on top of the original bracket.

I replaced the rivets that fasten the original bracket to the engine pan with bolts because they had become quite loose. There were signs of significant wear from vibration between the bracket and the engine pan. I felt that with the larger, heaver cooler that could only get worse.

The new cooler did not come with any hardware or rubber grommets. My original grommets were worn out so I did not reuse them.

I used a dermal to remove the old fiberglass “ramp” used to direct air for the old cooler.

You may have clearance issues between the cowling and the new cooler. That is one of the reasons I replaced old warn-out motor mount rubbers. It seemed to me that the engine sag was going to be a much bigger problem with the new cooler.

I did not take any on-purpose pictures of the new cooler installation. I did find some accidental ones that may be of use.

This first one shows a trial fit of the new cooler. I was attempting to learn if there would be a clearance problem. The old "ramp" is still in place and the old rivets too. You can see that the new cooler is longer then the old one.

In this picture you can see the new bracket extension I made out of angle stock.

Comment by Bob Simmons on October 15, 2009 at 6:55am
I didn't address Jabiru Pacific in my e-mail. Only the home company and Jabiru USA.
Comment by Phill Barnes on October 15, 2009 at 6:33am
Hi all
Below is a copy of my initial email to jabiru for all to see only omitting Steves private email address.

Hi Kody
I am in current communications with a man by the name of Stephen Smith from the US. He has had to do a major rebuild of his 3300 at 600hrs and wishes to find some kind of answer as to why mainly to help prevent it happening to others. He email Jabiru Australia once before and recieved no reply so I offered to help him communicate. Below are links to two blogs on his engine rebuild. Could you please personally make sure that this is delivered to the correct person within your company.

Here is Stephen's direct email, --------------------



Many thanks

I then followed up with Kody who works in the spare parts devision and he has put it accross to the engine department and will follow it up. Rod Stiff was standing next to him while he was talking to me on the phone so at the moment I can only assume that he is aware of the situation. Kody told me that in order to not tread on anyones toes, any questions from the US are usually to be dealt with by Jab USA or Jab Pacific. I informed him that there has been a lack of after sales service for many customers and that a response is needed even if only in the form of prompting Jab USA to communicate better with their customer.

I am waiting for a detailed email from Steve Smith to forward to Jab Aus and will touch base with Rod Stiff in a day or so to allow things to filter through the system.

I would like everyone to know that things tend to sound a little officious in emails sometimes but I assure everyone that I am not burning any bridges but helping build new ones with plenty of manners.

There are a lot of people who have no problems at all with their engines and I hope to be one of them. There seems to be a fine line between good or bad cooling. A Zodiac here in Aus was having some cooling problems with it's 3300 until they moved the baffle that stands up infront of the first two cylinder head closer to make it touch the fins. Now their engine temps are great, and that's in the tropics of north Queensland, very hot.

Any new info I recieve I will post here, with Steve's permission of coarse.

Phill Barnes
Comment by Bob Simmons on October 15, 2009 at 4:43am
Steve S., I didn't mean to imply that you were attempting to make things private. I was speaking for myself only. That's why I said I'd leave it up to you to decide the best course for your specific issues.

Your great documentation here is very much appreciated by all.

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