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Exhaust Valve Trauma

petehowell

Well Known Member
Well it finally happened...... After 1600 trouble-free hours with my O-320, a little rain has fallen. Made two great trips to Iowa last weekend and got home on Sunday and dropped the oil for the change. I made the mistake thinking on the way home how great she was running.......

I did my usual compression check and saw 77/80 on 2-3-4, but #1 was 60/80. Leak out the exhaust - grrrr (all 77/80 50 hrs ago). Talked to those more smarter than I (Professors Horton, Lane, Peterson, et al) and consensus was fly it a bit, test it again - that did not help - no joy. Exhaust leaks don't heal and need to be dealt with.

Made a "Mike Bullock Wonderbar Special" (TM) valve compressor(seriously, was that a great writeup he did or what!)

20160526_185338.jpg


Then pulled the springs and keepers. Valve was silky smooth in the guide and seated well when pulled back, so that was good. Dan suggested spinning and banging the valve on the seat just in case there was a piece of junk on there, so we tried that and shot this video thru the top plug hole with my celly.

watch


I think you can see the problem area if you look closely, but do offer up any observations of the valve sealing surface.

We did try a compression check after doing the "Spin and Bang" - same story 60/80 and exhaust hiss. Took me less than 30 min to get the baffling and other stuff out of the way to free up #1 Jug (it looks like the easiest of all to get free), then I had to go out of town for the weekend. Jug will come off tonight with the help of Alex P.

New jug looks to be $1000 or so. So New Cylinder, rebuilt cylinder, or fix the valve and seat........that is the question....please offer opinions, rationale and cost estimates.........

To answer the questions you are all dying to know....

- These are ECI Group B Cyls from 2005
- LOP other than takeoff, CHTS balanced and in the 325degF range
- 50+% Mogas, 92 no EtOH
- Carb
- E-Mag/Pmag
- Rattle can Primer
- Nosewheel
- Dog hair in the cockpit

Thanks for commiserating................ Ha!
 
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Oh the awful 1600 hour decision........

In the old days, rebuilding/fixing/overhauling jugs was just the norm - to try and get to TBO. But with a complete stud assembly (jug, piston, valves) for $1,000? Why bother! But then.....you've got one brand new jug and three others at 1600 hours! I had this same dilemma on the Val at 1400 hours, and decided that since the bottom end was first-run, and doing great, I'd bite the bullet, put four new jugs on (mine was a ring issue - all the jugs were suspect), and start doing oil analysis to look at the bottom end when I got closer to TBO. The first-run bottom end can go a LONG time.

The real question is if there is a good cylinder shop nearby that can just re-do the exhaust valve and seat for you for a few hundred bucks. If they can, and it were me, I might give that a try on this FIRST jug. If you start seeing a pattern, with another jug doing the same thing, then keep the whole engine in sync with an O/H or at least a top O/H with four new jugs.

It's been forty years since I lived in the Cities, so I have no idea if there's a good cylinder shop aroudn anymore.
 
Pete, I will leave the valve advice to others (my cylinders have 1200 hrs...) but I missed the "Mike Bullock Wonderbar Special" article. Where do I find it?
 
My buddy with a twin SuperCub to mine had one of those B group ECI jugs blow off, on take off (successful water landing thankfully). I personally do not see any choice, but that's me. We replaced 8 jugs at that time (same engine).
 
Hey Pete - just to me sure you might get a good visual on the other ex valves. If they are not crescent mooning, then minimal repair (like Paul said) and on to the real TBO.
 
Gibson's in El Reno, OK can overhaul the cylinder for $345 with a two day turn around. http://www.gibsonaviationok.com/

If you haven't already pulled it I would use a borescope to inspect further. The in-place lapping might work and is better than removing a jug, but you would want to see the seat first.
 
Pete,

Didn't you recently buy one of those inexpensive endoscopes/borescopes? if so, did you use it after discovering the leaky valve? I would love to see some pictures of the valve if you did.
Just curious because I got one of those scopes and will be using it for my inspection this summer.
 
About 20 years ago I had a first run 0360A4M overhauled at 2200 hours. I opted for new Millenium cylinders thinking that was smart. One of them failed 600 hours later.
At the time the OH shop advised the original Lycoming cylinders could have been cleaned up and would have continued running just fine.
I am flying with a Superior engine in the 8 but wonder if the after market products are as good as original Lycoming stuff.
Your engine should not be causing trouble at 1600 hours.
 
Exhaust Valve

This is only one step beyond routine maintenance. If all other engine parameters are good I would remove the cylinder and have a engine shop repair as necessary. Reface both valves and seats, hone cyl barrel and install with new rings, seals & gaskets. Break in as usual and fly off towards TBO. If you ship the cylinder be sure to pad/protect the upper end really well. If the box gets dropped head down the rocker bosses can be deformed. I have used Gibson several times before with good results.

Don Broussard. A&P/ IA

RV 9 Rebuild in Progress
 
Dental cam

Hi Bruce - I have a $35 dental cam - it shows the top of the valve pretty well and it looked fine - the vid thru the hole show the spot where the leak looks to be.

The local cylinder shop is gonna take a look and let me know - they thought the valves and rings looked good at first glance this morning.
 
Back in the Game!

I took the cylinder over to the engine shop Tues morning and they said it looked pretty good they could have it back to me by Friday. They called today and said pick it up!

I traded $400 for a new guide, exhaust valve, gasket set, and some labor. 45 min later the jug was back on. They said the rings and bore looked great, so just bolt it on and go!

All cleaned up:
20160601_184608.jpg


20160601_184735.jpg


I removed, cleaned and bled the lifters then checked the clearances, which were right at the lower limit. Quick compression check showed 78/80 - Booyah!! I'll get the baffles, intake and exhaust hooked up tomorrow night.

All in all, not as bad as expected. I did take a good look at the cam and lifters and they looked pretty good, too.
 
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Experimental vs. Certified

You mention the cost being $400 for this job. I wonder what that would've been in the certified world?

Pete - it doesn't help your pocket, but that price seems very reasonable. Gotta love experimentals.
 
Buldoc

Hi Guys,

I used Buldoc Aviation right here on the field at KANE - was easy to drop off and pick up and my guess is shipping a cylinder is not cheap.

Dave -they said the rings and bore looked great, so no hone was required - just bolt it on and go fly, so I will.
 
That sounds like a perfect solution in your situation Pete - keeps all the cylinders and bores "in synch" towards TBO.
 
You mention the cost being $400 for this job. I wonder what that would've been in the certified world?

Pete - it doesn't help your pocket, but that price seems very reasonable. Gotta love experimentals.

I suspect no difference in price. Bolduc is a great guy/shop. BTW, he's been a believer in LOP operations since waaay back.
 
She Flies!!!

Just to close this out - got her all put together and took her up for a few laps around the pattern - she felt great as always, but no longer hisses at me when I pull thru jug #1.

Thinking about pulling the jug to get it fixed, was way scarier that just doing it.
Glad to have it fixed - Andi found a pancake flyin over in Sconnie on Sunday morning!
 
100 + Hour Follow Up

I now have 100 hours on the #1 cylinder with the new ExValve. Compression is great at 78/80 and the CHTs dropped a bit from where they were before the repair.

It was cheapish and easy fix. I learned a few things along the way, too. Many thanks to all those that offered help and advice. I am lucky to have great crew here in Minne and 24/7 here on VAF.
 
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