EA81 Tear down

[Guest aussie carl]

Info from SamL on the rotorsport forum.

 

Compiled by Graeme Monro

 

http://www.asra.org.au/smf/index.php?action=dlattach;topic=3665.0;attach=3902

 

Looks like the EJ series are to porky for LSA

 

 

[Guest aussie carl]

Would be interesting to find out what the EJ15 and EJ16 weigh.

 

They have the ponies but are they porky.

 

 

[Russ]

http://www.800-airwolf.com/pdffiles/ARTICLES/decision.htm

 

Folks here might find this interesting.............

 

 

[Guest aussie carl]

I may have located another EA81 with only 120K K's on it.

 

Will find out more detals early next week.

 

 

[will kirkbride]

Hi again Carl. See you are on the Gold Coast, my home town. I am at my farm in the South Burnett to get away from the holiday crowds.

 

Hope to keep posting when I get back to work on tuesday.

 

The guys from Terrier are a little reluctant to part with info. Helmut is the main man and just loves the EA81. When I spoke to him,he told me he was an electronic engineer or something similar from memory, hence the new finger coil ignition setup he has on the website as an option.

 

If you have a chance to measure the width of the EJ series engines, you will see that they are probably too wide to fit inside the cowl of an ultralight of Jabiru size for example.

 

This is probably why they are used in gyro applications as well as the greater horsepower thing. they are considerably heavier than the EA81 series.

 

I have been finishing off my hanger while up here. Might post a photo later.

 

I should be at the Evans Head flyin on the SAAA stand weather permitting. Say hi if you end up going and I am there.

 

Cheers.

 

 

[Guest aussie carl]

Thanks Will.

 

Back home now.

 

I was hoping to get a closer look at an EJ15 or 16 just to see how big and heavy they are, just for interest sake.

 

Weather permitting we will be at Evans Head on Sunday.

 

 

[Guest aussie carl]

Looks like the cylinder has done a spark plug electrode. The damage is confined to the squish area in the chamber.

Just pulled another EA81 apart and would you believe it, an earth tab from a spark plug was fused to the bottom part of the thread inside the chamber. Another plug had been fitted obviously cause it was not firing on one of the cylinders but the tab from the old plug was still fused to the alloy and no damage had be done.

 

 

[Guest aussie carl]

have a look at thes pickies and spot the cracks

 

 

 

 

[stanzahero]

Common affair with these critters.

 

If it was a car, I'd remove the inserts, grind out the cracks (they don't look severe enough to hit the water jacket), weld up the holes and fit another larger set of welltite or martite inserts in them.

 

A straght forward job for any one with a TIG welder and a Serdi.

 

Altough I'm not sure as to the protocol with the aero engine community.

 

Stanzahero

 

 

[facthunter]

the cracks have not gone far enough to get near the water. Your main concern is the tightness of the insets in the aluminium. If the interference fit is not there they can come loose. Welding may not be a very premanent fix as it will end up in tension (as the weld cools) and likely to recurr. Some engines have the inserts intersecting. ( Not a practice that I like). Have the hardness of the head checked. ( sometimes they go soft and are discarded). You can heat the head quite hot and the inserts will usually fall out. After it is cooled you can check the dimensions of the recess and re-install the insets, (or new ones). Sometimes they use liquid nitrogen to shrink them and install them that way. ( Best method). Nev

 

 

[stanzahero]

It's a good point about the hardness make sure you get it checked.

 

Welding does generally not create tension if the head is allowed to cool slowly. I used to wrap the welded cylinder head in a thermal (asbestos) blanket and give it 12 hours to cool.

 

Like Nev said, interlocking inserts can be a problem because of the difficulty in getting them to both seat in correct alignment with the guides. Alloy tends to have more 'give' than the steel inserts so the second insert to go in will be pushed to the side. It also an issue when the head warms up, because the alloy head expands at a greater rate than the steel insert. This will also push the valve seating position off slightly causing abnormal guide wear because valve seats will move away from each other after warming up.

 

The standard interference (crush) for the valve seats are .007" - .008" for an alloy cylinder head and .006" - .007" for a cast iron cylinder head.

 

With the correct interference fit, they will not drop out unless the head is very soft, or the engine is in the process of being cooked well beyond normal limits.

 

They are reliable enough for just about every manufacturer to use is their engines (disregarding Datsun 1600s and Lamborghini with their bronze inserts).

 

Stan.

 

 

[Guest aussie carl]

Thanks for the usefull info fellas. I have acess to a NATA aproved lab for all the testing I need for free without cretificates.

 

So how hard should the heads be is the next question.

 

BTW I am discarding the heads shown but have more up my sleve.

 

 

[Guest ozzie]

If you aren't keen on playing with liquid nitrogen or cannot afford the stuff you can place the inserts/ guides in the freezer for a day and block off the water outlet/ inlets on the head and fill the water passages with hot kero and let the head warm up.

 

Interesting thread keep em coming. I have had no experience with a Subaru engine. So find it a new experience, closest would be a 6cyl Corvair i stuffed into a kombi years ago.

 

 

[Guest aussie carl]

But wait ! There's more.

 

One of the other two heads I have had part of a plug thread still in the thread.

 

I'd say the plug got jamed someone drilled it out and retapped the thread but only got most of the thread. (how do they do that)

 

There are no cracks in either of the two heads between the valve seats but this one is obviously RS because of the thread.

 

So out of four heads I now have one good one which still neesd to be hardness tested and crack tested. phew !

 

 

 

[facthunter]

Might be a good idea to get them pressure tested too. ALL Al. castings are porous. The best ones are vacu-cast (Cyl heads). To seal them some are infused with some kind of plastic. This treatment doesn't last forever and liquid-cooled motors are more critical. This is the problem with used engines. The EA 81's are pretty old now. You used to be able to buy new Volkswagen heads, pretty cheap (made in Brazil). Can the Subaru heads be purchased for a realistic price. (New).? Nev

 

 

[stanzahero]

OOh thata REALLY bad repair job!

 

Method for hardness testing:

 

First, the head needs to clean. No carbon, oil or sand-blasting residue on the faces to be tested.

 

There are a variety of tools that are used to test haardness, ranging from a fully electronic device to a calebrated hollow tube with a ball bearing in it.

 

They all work by dropping a ball bearing onto the surface and measuring the rebound.

 

Making sure that the tool is flat on the face of the head, test the head in about six or seven places. Include between the cylinders (not on any badly sunken gasket marks), above the exhaust port on the face, above the inlet port and on the rocker gasket rail as well.

 

Generally the higher the average the better but stats are about 65 Brinell as a throw away mark for any low result to about a 75 average min. The higher the average, the happier the head.

 

Nev, ALL cylinder heads should be pressure tested as a process of reconditioning - most preferably with a very hot photofloresent fluid. That way a black light will show any hairline cracks that would not normally be picked up.

 

 

[facthunter]

Re the last 2 lines, most cracks are caused by overheating, and are in fairly predictable locations. ie. between inserts and between the exhaust insert and the plug thread. Chemical cleaning and a simple dye check will detect these. You can often see them any how. Some times they can be ignored and the engine returned to service, but that would have to be based on experience with that engine type. What I was actually referring to is porosity. Some 2-stroke M/C crankcases leaked so much air that the mixture was affected. Porosity will resuly in loss of coolant and "hot " spots or worse, overheating in general. Nev

 

 

[Guest aussie carl]

Just bought another EA81 from wreckers, This one I got to hear and see running. Hopefully this one will be in better nick. edit $100

 

Irony is I need another/larger filter for my grit blasting cabinet. (auto air cleaner) a filter is $20 but I will use the on on the EA81, so the rest of the motor including alternator, and starter motor are cheap.

 

 

[fly_tornado]

expensive?

 

 

[Guest aussie carl]

Fly I added the edit to my post above. Motor cost $100. The clutch on this one is pretty new and I know I can sell it for $60 easy.

 

Now back on the last head of the 4 previous. It was hardness tested today. From 77-95 HB with an average of 89 HB (HB is Brinell) so it is a keeper so far.

 

Off to clean down the 3rd motor and strip it down.