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Fox Eagle III .60 Diesel Conversion

Old 08-20-2011, 08:49 PM
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earlwb
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Default Fox Eagle III .60 Diesel Conversion

I had acquired this engine, mainly to get the Davis Diesel Head, so the engine was more or less free then.
The poor engine was abused and appears to have been used a lot and it had a hard life. Someone had filed notches in the right mounting tab to clear a Streamline dual downdraft header exhaust. But for some odd reason they used aluminum foil to make a head shim for the engine. The compression screw was turned all the way in too. So I pulled the head off and removed the aluminum foil, cleaned and oiled the engine, and then reset the contra piston in the head after backing out the compression screw. I put it back together and it feels much better now and has some good compression again.

But what is most odd is the weird blowby pattern on the cylinder walls where the piston ring wasn't sealing it up like normal.
I hadn't seen a pattern like that before. There are an evenly spaced pattern of 16 spots where the blowby got past the piston ring on the engine. You can see it in the pic just below.

Anyway I plan on sending the engine in as a clunker and get a new Fox .60 to replace it with, but I'll keep the DDD head of course.
Replacing the needle valve, cylinder, piston, ring, wristpin retainer clips, wristpin and rod would cost more than using it as a trade in for a new engine. besides I have some other Eagle III engines anyway. I just mainly was trying to figure out how that odd cylinder blowby pattern had come about on the engine. Of course the engine feels pretty good now, so I might have to give it a test run to see how it does perform now.












After cleaning and oiling the engine and removing the aluminum foil. the compression screw has been backed out now as well.


Old 08-21-2011, 03:07 AM
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Default RE: Fox Eagle III .60 Diesel Conversion

Earl, unless its my imagination that cylinder appears to have been honed with too course of a hone, could those "streaks" be the result of hone chattering. One my older Fox Eagle .60s has the upper cylinder block like yours but a more modern crankcase.
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Old 08-21-2011, 04:42 AM
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Default RE: Fox Eagle III .60 Diesel Conversion

Yeah I too, was sort of thinking that maybe someone used a hone on the cylinder.
Probably a brake cylinder hone. Unfortunately, the Fox engines use a hardened on the inside cylinder sleeve, so using a hone makes it easy to machine off that hardened thin layer. I think that one has to make a cylinder hone, like Model Engine News shows, that is tapered to allow for a slight taper in the cylinder sleeve.

Yes your .60 engine is a early model Eagle IV before they upgraded the upper cylinder block with the current design. the Eagle III doesn't have the little stub fins on the front and back of the cylinder block.

Old 08-21-2011, 02:23 PM
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Default RE: Fox Eagle III .60 Diesel Conversion

As plausible as the 'hone' theory may be it has holes in it.

Ever seen a hone with 16 stones in it?
Or why the marks are dead vertical when honing is performed in a cross pattern? (See the rest of the cylinder walls to see the proper cross hatch pattern.)

Maybe its an extrusion weakness in the manufacture of the original liner?

And where is the blow-by going to? It doesn't seem to extend to the exhaust port and the pattern repeats  itself around and above TDC.

Strange.
Old 08-21-2011, 03:56 PM
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Default RE: Fox Eagle III .60 Diesel Conversion

ORIGINAL: Recycled Flyer

As plausible as the 'hone' theory may be it has holes in it.

Ever seen a hone with 16 stones in it?
Or why the marks are dead vertical when honing is performed in a cross pattern? (See the rest of the cylinder walls to see the proper cross hatch pattern.)

Maybe its an extrusion weakness in the manufacture of the original liner?

And where is the blow-by going to? It doesn't seem to extend to the exhaust port and the pattern repeats itself around and above TDC.

Strange.
Cylinder Hones don't all have stones.

I'd take a wild guess at a ring that simply hasn't bedded in yet and the pattern simply reflects leakage at the most out of round locations around it's circumference. I believe that rings can be ground to their OD on a centreless grinder which could produce the hexakaidecagon pattern rather than a circular one.

Ray
Old 08-21-2011, 04:21 PM
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Default RE: Fox Eagle III .60 Diesel Conversion


ORIGINAL: locktite401
Cylinder Hones don't all have stones.

I'd take a wild guess at a ring that simply hasn't bedded in yet and the pattern simply reflects leakage at the most out of round locations around it's circumference. I believe that rings can be ground to their OD on a centreless grinder which produces such a pattern.

Ray
Hi Ray,
Yep, some hones are the ball type but how would you ever get that striated pattern with a ball hone?

Th ring theory I like though!

Cheers.

Old 08-21-2011, 04:36 PM
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Default RE: Fox Eagle III .60 Diesel Conversion

Like that free form art decco head gasket martin
Old 08-21-2011, 05:35 PM
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Default RE: Fox Eagle III .60 Diesel Conversion

I'll posit another theory...the ring had insufficient end gap and when the ends butted, the ring went into a sinusodial shape to accommodate its size and the blowby pattern is the result. Of course, the ring would not be able to rotate for the pattern to occur.

John C
Old 08-21-2011, 05:49 PM
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Default RE: Fox Eagle III .60 Diesel Conversion


That Fox must set new standards for ugliness even for Fox!

Old 08-21-2011, 06:15 PM
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Default RE: Fox Eagle III .60 Diesel Conversion

It is actually a 'Transformer' - Optimus Fox reporting!(Or a Deceptacon - depending on your point of view.)
Old 08-21-2011, 06:28 PM
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Default RE: Fox Eagle III .60 Diesel Conversion

It needs more foil ( the whole engine) martin
At least you have a great head
Kidding aside get the right head gasket, if engine ok good compression, bearings etc it should run fine
or your original idea trade for a new one
Old 08-21-2011, 07:24 PM
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Default RE: Fox Eagle III .60 Diesel Conversion

AMB, they don't use head gaskets on this type of engine. Now for a glow engine, you might need a shim or two if you were running higher nitromethane percentages, ButFox does not make shims. One technique they did was make different combustion chamber shapes though, that would have the same effect as using a head shim or two.

locktite, that is a 30 some odd year old engine. The newer version has been upgraded considerably since then. But it still maintains a similar design layout. Back in 1981, Fox wasn't interested in copying those other brand of engines to make them look pretty. he was interested in what was inside more though. At the time the Eagle III was also the base for the twin 1,20 engine too. The rotatable cylinder was a feature like they use on the MVVS engines too. But you may still get parts for the Eagle III from Fox, how many other brands besides Enya can you still buy parts for them that old? it just isn't worth trying to fix it when I can use it to get a new one though. Maybe if I had several clunker engines, I could swap parts around, but all the other ones I have work fine though. Besides beauty is in the eye of the beholder. I think they looked pretty good myself. But then I do have a bunch of Fox engines. The latest Fox Eagle IV looks much nicer though.

Anyway, I am in agreement that it looks more and more like the piston ring was not fitted correctly and did not have a ring gap resulting in the odd wavy pattern for the blow by effects when the ring heated up and expanded and had no place to expand into. I suspect the previous owner had replaced the ring and didn't check the ring gap. You can usually replace the piston ring at least three or four times on a Fox engine before the cylinder wear down too much.

Well at least a previous owner didn't use lots of red gasket sealant all over the engine, like I have seen them do before on engines. Not just Fox engines either.

Now I just remembered that the first batch of Eagle III engines had high compression heads intended for FAI fuel or zero nitro glow fuel. So maybe way back in 1981 someone kludged it with the aluminum foild head gasket to lower the compression a little for nitro glow fuel. Years later someone tried a DDD head on it. But it had been pretty much abused and worn down by then.

Old 08-22-2011, 03:32 AM
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Default RE: Fox Eagle III .60 Diesel Conversion

Fox does have head shims but you have to ask Sharon for them. I still think someone made a half hearted attempt to hone it, possibly with sand paper. The no ring gap theory does have merit though. I have about three ring, piston and cylinder sets for a Fox .50, all used, I fitted different pistons and rings into different cylinder until I got what I thought was a perfect fit. On one ring and cylinder combo the piston would only go half way up the cylinder and stop. I did not gap that ring but used it in a cylinder where it moved freely. One cylinder has a very obvious wear ring near the top where the piston ring travel stopped.
Old 08-23-2011, 12:23 PM
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Default RE: Fox Eagle III .60 Diesel Conversion

Could be an air in-leak arround the eight head screws?
Old 08-23-2011, 01:40 PM
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Default RE: Fox Eagle III .60 Diesel Conversion

Yeah, that is possible. It is a unknown engine as to its history. But it looks like someone had dinked around with the cylinder/piston and ring. They could have tried to shave a little off the top of the cylinder sleeve too.
I plan on test running the engine a little before I send it in for a trade in on a new engine. i am curious as to why they had the aluminum foil on it too.
So I wanted to see what happens with the engine myself.
Thanks

Old 08-23-2011, 02:23 PM
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Default RE: Fox Eagle III .60 Diesel Conversion


ORIGINAL: earlwb
.......... how many other brands besides Enya can you still buy parts for them that old?
Goooood question, 30 year old engine parts availabilty -
PAW.
MVVS.
Taipan.
Cox.
Oliver.
K&B?

Come, help me out here!
Old 08-24-2011, 09:02 PM
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Default RE: Fox Eagle III .60 Diesel Conversion


ORIGINAL: John C

I'll posit another theory...the ring had insufficient end gap and when the ends butted, the ring went into a sinusodial shape to accommodate its size and the blowby pattern is the result. Of course, the ring would not be able to rotate for the pattern to occur.

John C
I've been thinking about this one! It seems to me that too little end gap would have the opposite effect to what's evident here. Perhaps too much end gap could result in very marginal sealing by the ring allowing the leakage pattern shown.

Ray
Old 08-25-2011, 03:44 AM
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Default RE: Fox Eagle III .60 Diesel Conversion

Another possibility that has not come up is that the head bots are way over tight. This would create a uniform pattern.
Old 08-25-2011, 07:25 AM
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Default RE: Fox Eagle III .60 Diesel Conversion

Of course, since the odd wear pattern is in the high wear zone on a engine cylinder, that portion of the cylinder may be really worn down good, and the ring is just not sealing it well anymore. Thus the odd blow by pattern is just a artifact of the ring not working well anymore.

Old 08-25-2011, 12:02 PM
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Default RE: Fox Eagle III .60 Diesel Conversion

I think Hobbsy nailed it!
Old 08-25-2011, 04:46 PM
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Default RE: Fox Eagle III .60 Diesel Conversion

I don't know...there are eight head bolts and lots more blowby indications per the first picture.

John C
Old 08-25-2011, 07:13 PM
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Default RE: Fox Eagle III .60 Diesel Conversion

16 evenly spaced marks, 8 evenly spaced head bolts ................. hmmm, uncanny coincidence? Coupled with the fact that the foil was undoubtedly used to get a good seal and what precludes that almost every time? A ham fisted torque setting! I too think that Hobbsy has nailed this one good and proper.
Old 08-25-2011, 10:12 PM
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Default RE: Fox Eagle III .60 Diesel Conversion


ORIGINAL: Recycled Flyer

16 evenly spaced marks, 8 evenly spaced head bolts ................. hmmm, uncanny coincidence? Coupled with the fact that the foil was undoubtedly used to get a good seal and what precludes that almost every time? A ham fisted torque setting! I too think that Hobbsy has nailed this one good and proper.

Except that the "features" are just far enough down the bore to coincide with the ring at tdc.

Ray
Old 08-26-2011, 12:58 AM
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Default RE: Fox Eagle III .60 Diesel Conversion


ORIGINAL: locktite401


ORIGINAL: Recycled Flyer

16 evenly spaced marks, 8 evenly spaced head bolts ................. hmmm, uncanny coincidence? Coupled with the fact that the foil was undoubtedly used to get a good seal and what precludes that almost every time? A ham fisted torque setting! I too think that Hobbsy has nailed this one good and proper.

Except that the "features" are just far enough down the bore to coincide with the ring at tdc.

Ray
I believe that the blowby marks are all below TDC 401.

What are you aiming at here?

Old 08-26-2011, 02:15 AM
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Default RE: Fox Eagle III .60 Diesel Conversion

ORIGINAL: Diesel Fan


ORIGINAL: locktite401



Except that the ''features'' are just far enough down the bore to coincide with the ring at tdc.

Ray
I believe that the blowby marks are all below TDC 401.

What are you aiming at here?

Just to clarify. I meant that the individual "features" are symmetrical mirror images around a horizontal centreline that would coincide with about where the ring would be when the piston was at tdc. I still think that they suggest that the ring was leaking.



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