Experience with Subaru at 358 Hours

rv6ejguy · #1 01-31-2013, 10:50 AM

Some insight into things learned on teardown and inspection on our Sube powered 6A. http://www.sdsefi.com/rv16.htm

Mike S · #2 01-31-2013, 11:00 AM

Did the piston come out with the ring gaps lined up like in the photo??

All in all, this looks like a pretty minimum of wear------

Did you nail down the oil consumption cause?

rv6ejguy · #3 01-31-2013, 11:05 AM

No, ring gaps were not lined up like this, I positioned them this way to show how the upper ring was relaxed in relation to the 2nd ring which had the same free gap as new rings.

I really did not see anything significant to cause this level of oil consumption. I was looking for something obvious. A bit of a mystery and I don't like mysteries...

When the engine was built and for the first 200 hours or so, the engine used essentially no oil- less than a 1/2 quart in 35 hours when I would change it.

jcaplins · #4 01-31-2013, 11:47 AM

I am quite interested in seeing how that new cooling system works out.

TS Flightlines · #5 01-31-2013, 01:00 PM

Russ---are the cylinders tapered, with more skirt clearance near top?
Tom

rv6ejguy · #6 01-31-2013, 01:17 PM

Quote:

Originally Posted by TS Flightlines

Russ---are the cylinders tapered, with more skirt clearance near top?
Tom

With liquid cooled engine we don't do that as there is little difference in cylinder dimension on a warm engine unlike an air cooled one. There is taper built into the pistons as there is a fair temperature gradient top to bottom there.

The wear you see on only one skirt only is due to these forged pistons not having the wrist pin offset like the OEM pistons.

zav6a · #7 01-31-2013, 01:53 PM

I get the biggest kick out of tearing down an engine - so thanks for sharing!

Apparently no observable wear on cam or followers?

Put the old valve springs in?

I would bet the cyls are glazed. I have no idea of the phyiscs for that happening on a broke in, water cooled engine but I have had a couple of air cooled that had the exact same symptoms. Essentially no measurable wear on piston or cyls, rings that had lost temper, (obviously wirey instead of brittle), lots of blowby, oil that turned black more quickly that it should and high oil consumption. I can convince myself your cyls look just a little yellow.

rocketbob · #8 01-31-2013, 02:28 PM

Looks to me like the hone on the cylinders wasn't done very well. The angles look way too shallow. You might want to talk to your ring manufacturer and see what Ra (avg) Rpk (peak roughness) and Rvk (valley roughness) numbers to shoot for on the hone and check with a profilometer.

And are those push on fittings for the oil cooler??

DanH · #9 01-31-2013, 04:52 PM

When you think about the unusual rod bearing damage, consider how hard the crank is oscillating those rod throws during your 1100 to 1600 RPM resonant period.

rv6ejguy · #10 01-31-2013, 06:13 PM

Quote:

Originally Posted by zav6a

I get the biggest kick out of tearing down an engine - so thanks for sharing!

Apparently no observable wear on cam or followers?

Put the old valve springs in?

I would bet the cyls are glazed. I have no idea of the phyiscs for that happening on a broke in, water cooled engine but I have had a couple of air cooled that had the exact same symptoms. Essentially no measurable wear on piston or cyls, rings that had lost temper, (obviously wirey instead of brittle), lots of blowby, oil that turned black more quickly that it should and high oil consumption. I can convince myself your cyls look just a little yellow.

Valvetrain was all mint except replaced all the valves because they had been reground once and did not have enough margin to do again. Did this engine the same way I built 200+ race and performance engines as far as pistons, rings, hone grit. Never had a glazed cylinder yet or an oil consumption problem on any of them, ring faces looked normal, everything looks normal. Yellow tinge is W/B on camera setting and incandescent lighting I think.