Author Topic: Interesting exhaust valve (Read 9664 times)

Triple Jim · « **Reply #1 on:** March 19, 2015, 09:02:26 AM »

I've had exhaust valves fail, but never like that one. Were there any symptoms? Clearly you narrowly missed horrible damage.

huub · « **Reply #2 on:** March 19, 2015, 09:08:14 AM »

that one was milliseconds away from snapping....

Tobit · « **Reply #3 on:** March 19, 2015, 09:09:06 AM »

What do the head and piston look like? How much did it stretch? I've never seen one like that.

John A · « **Reply #4 on:** March 19, 2015, 09:25:25 AM »

Unfortunately I don't know what engine it came out of, the old guy that gave it to me said the engine had a miss and lacked power. otherwise everything else was in ok shape. Ive never seen one like that, obviously ready to drop! I thought about posting it as a Lario exhaust valve, just for humor.

Penderic · « **Reply #5 on:** March 19, 2015, 09:29:23 AM »

That valve face will have to be reground. ;D

rodekyll · « **Reply #6 on:** March 19, 2015, 03:07:24 PM »

VW aircooled cyl#3 exhaust valve. It's a classic.

normzone · « **Reply #7 on:** March 19, 2015, 03:31:33 PM »

I understand what I'm seeing but not how it gets that way. Is it a combination of stretched and etched ?

Bill Havins · « **Reply #8 on:** March 19, 2015, 03:39:19 PM »

Quote from: rodekyll on March 19, 2015, 03:07:24 PM

VW aircooled cyl#3 exhaust valve. It's a classic.

Tell us more, please.

LowRyter · « **Reply #9 on:** March 19, 2015, 04:06:33 PM »

my goodness. :pop

redrider · « **Reply #10 on:** March 19, 2015, 06:26:51 PM »

I noticed the head and stem are not perpendicular. Now on to an oil thread.....

rodekyll · « **Reply #11 on:** March 19, 2015, 07:01:27 PM »

#3 cyl on an aircooled VW lives behind the airflow of the cooling fan because the oil cooler tower (sits inside the fan shroud) is blocking it. It is also at the point of least oil to the rod big ends, and is next to the only split main bearing on the crank. Because of all that the dizzy was set for 5º retarded timing for #3 and for some engines the #3 valves were set to looser specs.

People who didn't understand would set the dizzy 180º out and time to cyl3 innstead of cyl1. That made everything 5º more advanced, resulting in a hotter cyl3.

VW valves came in several flavors, some one-piece, some with a stem-and-head welded together. This second type often had sodium filled stems for heat dissipation. The two-piece valves would shed a head when it failed, launching a flying saucer through the top of the piston and into the nether regions of the crankcase. The one-piece were more forgiving -- they would stretch as in the picture, but not so extreme. The mechanic got a sense of imminent failure from rapid changes in valve lash. If he noticed it in time he could be proactive. If not, the stretch would eventually result in zero or (-) lash and the valve would burn, stretch rapidly, and eventually break.

The valve in the picture is stretched beyond belief -- I would expect breakage or piston contact after no more than a mm or two stretch, and I expect when that happened that the head would either be significantly tweaked to one side or missing entirely. I suspect the picture has been enhanced, since there isn't a head space made to accomodate that length, and of course when the piston began battering the valve head, the effects would have been catastrophic. There is no evidence of the valve having made contact with the piston.

John A · « **Reply #12 on:** March 19, 2015, 07:14:29 PM »

Maybe it came out of a side valve, the guy that gave it to me works on small engines, old Cub Cadetts and stuff. No the picture has not been enhanced or changed in any way. I took the pictures.

rodekyll · « **Reply #13 on:** March 19, 2015, 07:17:53 PM »

It would depend on the original length of the valve. If the original length is really close to the current length, then this is not a simple stretched valve -- it's a welded or braised one where the joint is eroding.

John A · « **Reply #14 on:** March 19, 2015, 07:27:24 PM »

I didn't measure the length since I don't know what it's sposed to be. I do think it is eroded, not stretched.

rodekyll · « **Reply #15 on:** March 20, 2015, 03:22:52 AM »

Could it be from a marine or industrial engine?

John A · « **Reply #16 on:** March 20, 2015, 05:00:12 AM »

I'll try to find out, hopefully the old guy remembers. I bought this house from him and usually see him at Legion meetings. With an 8 mm stem it could have a bunch of applications. I think about it sometimes while running at wide open throttle.......that one wouldn't make it to wot!

creaky99 · « **Reply #17 on:** March 20, 2015, 10:50:27 AM »

Can we be sure that someone didn't use an acetylene torch on it for art's sake?

John A · « **Reply #18 on:** March 20, 2015, 11:32:39 AM »

Not in this circumstance, I can be sure it is as removed

Rough Edge racing · « **Reply #19 on:** March 20, 2015, 11:40:10 AM »

Quote from: rodekyll on March 19, 2015, 07:01:27 PM

People who didn't understand would set the dizzy 180º out and time to cyl3 innstead of cyl1. That made everything 5º more advanced, resulting in a hotter cyl3.

I am not a VW guy...but...advance d timing like 5 degrees, if the engine doesn't detonate and not run a full throttle constantly, will tend to reduce engine temperatures..Retar ded ignition spark means the combustion event comes later and some of the still burning mixture leaves the cylinder on exhaust stroke, raising head, exhaust valve and exhaust system temperatures. Many including me have seen red hot exhaust headers from retarded spark timing...

dilligaf · « **Reply #20 on:** March 20, 2015, 11:47:29 AM »

What Tobit said. ??? :BEER:
Matt

Guido Valvole · « **Reply #21 on:** March 20, 2015, 01:03:10 PM »

Ah, air-cooled VW #3 exhaust valves… I had one of those, and a 100-mile per day roundtrip commute, and didn't check clearances for too long. Was rewarded by a sudden seizure while coming home one night. Hwy 29 south of Napa CA, by the airport, midnight and raining. Just a sudden lockup of the rear wheels. Clutch in, coast to side of road, walk a mile or so to the nearest phone booth (1975, cell phones wouldn't be invented for a while)… I got a nice paperweight out of that. The ragged hole in the piston top means it's a lousy ashtray.

That taught me to be obsessive about valve clearance checks. So when the Monza started going from a happy and healthy .008 to .004 in about 500 miles I knew it was time to send the heads out for new exhaust valves. It's not just Larios!
cr

cruzziguzzi · « **Reply #22 on:** March 20, 2015, 01:36:39 PM »

Quote from: john A on March 19, 2015, 07:14:29 PM

Maybe it came out of a side valve, the guy that gave it to me works on small engines, old Cub Cadetts and stuff. No the picture has not been enhanced or changed in any way. I took the pictures.

Exactly where I went upon seeing it. Side valve/flat head. I've seen that and broken in those head designs probably a half dozen times..

Me, I'd weld it up grind it down and drive on. ;-T

rodekyll · « **Reply #23 on:** March 20, 2015, 02:23:41 PM »

Quote from: Rough Edge racing on March 20, 2015, 11:40:10 AM

I am not a VW guy...but...advance d timing like 5 degrees, if the engine doesn't detonate and not run a full throttle constantly, will tend to reduce engine temperatures..Retar ded ignition spark means the combustion event comes later and some of the still burning mixture leaves the cylinder on exhaust stroke, raising head, exhaust valve and exhaust system temperatures. Many including me have seen red hot exhaust headers from retarded spark timing...

I'd take that up with the engine designers.

John A · « **Reply #24 on:** May 05, 2015, 09:21:30 PM »

I just talked to Ken, he is the old timer that repaired the engine. He said it was a Kohler flat head in a golf course mower and it had a air leak. It ran rough. Didn't get to talk long, it was at our Legion meeting and we had a bunch of business to get through. I think when one of my aviation type friends retires, I'll mount it on a plac saying what a great mechanic he was.

normzone · « **Reply #25 on:** May 05, 2015, 09:43:31 PM »

Thank you for the update. Suddenly I feel like adjusting my valves.

Kentktk · « **Reply #26 on:** May 05, 2015, 10:48:28 PM »

This is correct.

Quote from: Rough Edge racing on March 20, 2015, 11:40:10 AM

I am not a VW guy...but...advance d timing like 5 degrees, if the engine doesn't detonate and not run a full throttle constantly, will tend to reduce engine temperatures..Retar ded ignition spark means the combustion event comes later and some of the still burning mixture leaves the cylinder on exhaust stroke, raising head, exhaust valve and exhaust system temperatures. Many including me have seen red hot exhaust headers from retarded spark timing...

This is not.

Quote from: rodekyll on March 19, 2015, 07:01:27 PM

People who didn't understand would set the dizzy 180º out and time to cyl3 innstead of cyl1. That made everything 5º more advanced, resulting in a hotter cyl3.

lucky phil · « **Reply #27 on:** May 06, 2015, 06:09:30 AM »

The valve stem isn't stretched its eroded. Due no doubt to the massive amount of combustion gasses leaking past the totally shagged sealing face.
Ciao

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Author Topic: Interesting exhaust valve (Read 9664 times)

Penderic

Bill Havins

redrider

Rough Edge racing

dilligaf

Kentktk