Stuck valves

[Bruce Fenstermacher]

Eric

While I don't have the numbers in my head for the right size reamer I'd say there really isn't a right size. When I did my cylinders I miked each valve and reamed the new guides to have the tolerance required.

Assuming the same was done to your engine then you shouldn't be removing ANY metal. If your guide was tight and you just opened it up then you did no harm. If it was loose, with out the cabin build up and you opened it up further then you may have opened it up to far.

I've done 10 cylinders and never removed any metal.

In my experience if one valve stuck there while be at least another if not more ready to stick.

[GAHorn]

Just for reference, the Ovhl Manual gives the clearances for the valve stem-to-guide. New limits are .003 min .0045 max and service limit (which would apply to repairs such as this) is .008.

[N170BP]

I carry a quart of TCP around with the syringe applicator
when flying places where I'm unlikely to find mogas (bringing
it with me to McMinnville this weekend...).

FYI, when I had one exhaust valve stick, I checked the
other 5, and 1 other one was very close to sticking as
well, and another was a bit tight.

Switched to a mogas/100LL blend or 100LL/TCP and have
had no problems since.

The EAA auto fuel STC says 82UL is approved in addition
to the mogas specified. When can we expect to see
82UL for sale at airport fueling stations?

[zero.one.victor]

I didn't just haphazardly grab a reamer & start hoggin' out the guide. Somewhere in my C145 info (can't find it just now, must be at the hangar) it called out exh guide ID = .437-.438". Then the Continental OH manual table of limits sez exhaust valve in guide min .0035 max .0055 service limit .008, for the O300 it sez min .003 max .0045 service limit .008. The valve stem miked out at .434", so a .437 reamer gives me that .003" min clearance. Perfect!
The comment about "shouldn't be removing ANY metal" was my original thinking, however who's to say that the guide ID/stem OD was done right at the factory? I had new ECI cylinders installed at OH. A friend of mine is buddy's with a TCM rep who is not too big on ECI cylinders because evidently he's seen numerous cases where they are not reamed big enough. Maybe they're trying to avoid the loose guide/wobbly valve/eroded seat that Continental top ends seem to be plagued by? It was also suggested that ECI might be "pre-reaming" the guide before pressing it into the cylinder, instead of after?
Anyway Bruce, if you didn't remove any metal,just CC (carbon & crap), good on ya. Your guides musta been sized correctly. Mine evidently was not. I'm gonna just soldier on for now, but I have a suspicion that (like you said) if one valve stuck maybe the others aren't far behind. I'll keep that in mind, and maybe do the other five this winter if I get ambitious.

Eric

[cessna170bdriver]

I'm gonna just soldier on for now, but I have a suspicion that (like you said) if one valve stuck maybe the others aren't far behind. I'll keep that in mind, and maybe do the other five this winter if I get ambitious.

Eric

Eric,

If you did your first one in 2 hours, I bet each of the rest will go quicker. Even at 2 hours each, it sounds like cheap insurance to me. If you ever have one stick in flight you'll wish you had (BTDT).

Miles

[Bruce Fenstermacher]

I didn't just haphazardly grab a reamer & start hoggin' out the guide. Somewhere in my C145 info (can't find it just now, must be at the hangar) it called out exh guide ID = .437-.438". Then the Continental OH manual table of limits sez exhaust valve in guide min .0035 max .0055 service limit .008, for the O300 it sez min .003 max .0045 service limit .008. The valve stem miked out at .434", so a .437 reamer gives me that .003" min clearance. Perfect!

Having communicated with you over the last few years I didn't think you did just pick up any old reamer but someone new might have read your post and thought so

The comment about "shouldn't be removing ANY metal" was my original thinking, however who's to say that the guide ID/stem OD was done right at the factory? I had new ECI cylinders installed at OH. A friend of mine is buddy's with a TCM rep who is not too big on ECI cylinders because evidently he's seen numerous cases where they are not reamed big enough. Maybe they're trying to avoid the loose guide/wobbly valve/eroded seat that Continental top ends seem to be plagued by? It was also suggested that ECI might be "pre-reaming" the guide before pressing it into the cylinder, instead of after?
Anyway Bruce, if you didn't remove any metal,just CC (carbon & crap), good on ya. Your guides musta been sized correctly. Mine evidently was not. I'm gonna just soldier on for now, but I have a suspicion that (like you said) if one valve stuck maybe the others aren't far behind. I'll keep that in mind, and maybe do the other five this winter if I get ambitious.

As you've done the math above and using the proper reamer for your application you got valve guide metal then appearently your guides where to tight. This may have helped cause the sticking.

[zero.one.victor]

At the hangar today I looked thru the Continental C-145/O-300 overhaul manual X-30013. Section 10 table IX table of dimensions (page 23) lists exhaust valve guide bore: .437-.438" . Section 13 table of limits lists exhaust valve in guide: .003-.0045", service limit .008" .
Couldn't find a listing for exhaust valve stem diameter.

Eric

[rudymantel]

Eric, I'm with you- I use car gas unless I'm on the road and it's not available-
Rudy

[GAHorn]

Eric, I'm with you- I use car gas unless I'm on the road and it's not available-
Rudy

No wonder your tailwheel keeps getting loose!

[zero.one.victor]

............................ and have cleaned
the exhaust valves/guides on the right bank of cylinders (still
have to do the left bank). ..................!

So Bela, did you do the other bank of cylinders? A later post sounds as if you did.
I was wondering if you "cleaned" the guides as per your original post- by lapping them with the valve stem? Or if you decided to use a reamer or some other tool?
I meant to ask you this when next I saw you, but it slipped my mind when I ran into you guys Sunday.
I'm still planning on doing the other 5 on mine this winter sometime.
Probably gonna buy a .437 or .4375 reamer before then,& maybe a valve-
spring compressor. Or are you guys who use the screwdriver(s) happy with that method? I might buy a little bore light ("bend-a-light") too- that seems like a handy little tool for any number of jobs.

Eric

[Bruce Fenstermacher]

Eric

The screw drivers work and I wouldn't let having to use them stop me from doing the valves. A purpose made tool that fits would make this job easier. As a guide to you I choose not to bid $22.50 for one at the convention opting instead to make one or use the screw drivers for the few occasions I needed to do this work.

The light would be a help I'd think. I made my own by taking a mini mag lamp and soldering a some twisted solid phone wire to it about 2 feet long. On the other end I took a regular flash light bulb. Carefully breaking and removing the glass portion of the bulb then cleaning the base socket thats left so that I could solder the wires to it and the tip. When done the base socket will fit any 2 cell flash light with the lens removed to power the bulb.

I originally designed this light to go into the 3/8" fork hole on the end of my Cub struts to inspect them inside. The light works for cylinders as well but a larger bulb like a regular flash light bulb instead of the mini mag bulb will put off more light and may be better in the cylinder situation.

[N170BP]

So Bela, did you do the other bank of cylinders? A later post sounds as if you did.
I was wondering if you "cleaned" the guides as per your original post- by lapping them with the valve stem? Or if you decided to use a reamer or some other tool?
I meant to ask you this when next I saw you, but it slipped my mind when I ran into you guys Sunday.
I'm still planning on doing the other 5 on mine this winter sometime.
Probably gonna buy a .437 or .4375 reamer before then,& maybe a valve-
spring compressor. Or are you guys who use the screwdriver(s) happy with that method? I might buy a little bore light ("bend-a-light") too- that seems like a handy little tool for any number of jobs.

Eric

I lapped / cleaned the valve stems in place. Not a peep of trouble
since, but I am religously using a mixture of mogas + 100LL and/or
adding TCP when I can't get Mogas (squirted some TCP in each tank
upon fueling up at Scappoose for the flight home this weekend).

Also, more than one person has since suggested using a flex-hone
instead of a reamer (Snap-On sells one that is the right size
range for our valve guides).

Either way you do it, more than one person has also suggested
using Kroil as the lubricant / solvent to help clean the guides up
(whether using a reamer, lapping in place or a flex-hone).

[lowNslow]

Saw this tool at Aircraft Tool Supply.

http://www.aircraft-tool.com/shop/detai ... x?PageNo=1

[Tom Downey]

this can't harm a valve guide, even if your a klutz like me.


http://www.aircraft-tool.com/shop/searc ... UCT_ID=GB9

[zero.one.victor]

Tom, BTW, the tools you posted a link to (.354 & .375 hones) are both the wrong size for the C145 exh guide. These hones & cleaners are probably great for a dirty guide, but I think that a regular reamer is probably a better bet if your guides were initially too small (under-reamed) as I suspect mine were.
I searched this aircraft-tool.com site and found a .437" reamer (p/n RMR-7/16) for about $17 but it appears to have a plain round shank, I assume for chucking up in a drill press or mill. The one I used had a square shank-tip for turning with a wrench or big tap wrench. Anybody have a link to an affordable reamer configured like that?


Eric