What's wrong with this picture? Part 2

[duaneage]

I'm sure you realize this but check the guides, especially the casualty hole. That head might not be worth the money, I would look for a donor head to replace it with. There are plenty available if you are patient.

 

[ALB80-850]

carb and valve

carb and valve

Greetings all,

I have a complete #3 carb that nees to be rebuilt. It can be yours for the cost of shipping. I may be able toolocate a valve as well. If the bone yard where I took what was left of my crashed bike still has it, I should be able to get one. I am not sure if the whole head assembly made it through the crash or not, but that too may be an option. The #1 plug hole will need a heli-coil, the last shop I had it in x threaded the plug. let me know if your interested.

Andy

 

[Nessism]

I'm curious about this engine as well. The valve head breaking off is a major concern. I wonder if the tie-wrap under one side of the valve head caused a bending load on the valve which led to the valve snapping in two? The valve should be tougher than this normally but when those exhaust pipes got red hot the exhaust valves would have gotten goodly cooked - possibly damaging them.

Good luck with this one Steve and give us an update when you figure out what's going on.

 

[TheCafeKid]

Greetings all,

I have a complete #3 carb that nees to be rebuilt. It can be yours for the cost of shipping. I may be able toolocate a valve as well. If the bone yard where I took what was left of my crashed bike still has it, I should be able to get one. I am not sure if the whole head assembly made it through the crash or not, but that too may be an option. The #1 plug hole will need a heli-coil, the last shop I had it in x threaded the plug. let me know if your interested.

Andy

Andy, for sure interested. The carb would be great, not a big deal needing rebuilt as Steve is already on the case with those. If you can get to a valve that would be great as well. Its an exhaust valve. Dont really need the head, unless you're not wanting to pull the valve out yourself. Send me a PM with shipping cost and what not. Thanks!

TCK

 

[TheCafeKid]

I'm curious about this engine as well. The valve head breaking off is a major concern. I wonder if the tie-wrap under one side of the valve head caused a bending load on the valve which led to the valve snapping in two? The valve should be tougher than this normally but when those exhaust pipes got red hot the exhaust valves would have gotten goodly cooked - possibly damaging them.

Good luck with this one Steve and give us an update when you figure out what's going on.

The valve itself has no signs of "cooking" I am inclined to think that perhaps the wire tie trick, combined with the limited surface area left behind from the plug tap PLUS *my* personal theory that the valve may have had a hairline fracture in it to begin with, put just enough lateral torque on it to snap it. Steve may think otherwise, but again the valves themselves look ok to me. After cleaning the head, it doesnt look at all like there are defects in it either.

 

[Dogma]

The valve itself has no signs of "cooking" I am inclined to think that perhaps the wire tie trick, combined with the limited surface area left behind from the plug tap PLUS *my* personal theory that the valve may have had a hairline fracture in it to begin with, put just enough lateral torque on it to snap it. Steve may think otherwise, but again the valves themselves look ok to me. After cleaning the head, it doesn't look at all like there are defects in it either.

I'm inclined to agree with the hairline crack theory. That break line seems to indicate some kind of defect in the stem before it finally broke. Or possibly a nick in the stem from rough handling and then fatigue failure. Hard to say without getting a real close look at the fracture zone.

It shouldn't have been a heat issue... IIRC it was 1 & 4 that were glowing.

I don't think it was the wire ties either. If the valve spring puts that much tension on the valve, then there would be a lot more damage to the wire ties than I saw when I did this to mine. Rereading the account... It's not clear if the broken valve ever had a wire tie under it. I think not, otherwise the break would have been noticed while trying to remove the shim on that valve. If I'm wrong on that, maybe the wire tie revealed the existing flaw.

Either way, y'all should be thankful it didn't pop off while it was running. I've seen what that can do to an aluminum head, and there wasn't much left of the piston. The good end of that head was was sawn off and used on another project...

With this being a mystery, are you planning to replace only the broken valve?

 

[TheCafeKid]

I'm inclined to agree with the hairline crack theory. That break line seems to indicate some kind of defect in the stem before it finally broke. Or possibly a nick in the stem from rough handling and then fatigue failure. Hard to say without getting a real close look at the fracture zone.

It shouldn't have been a heat issue... IIRC it was 1 & 4 that were glowing.

I don't think it was the wire ties either. If the valve spring puts that much tension on the valve, then there would be a lot more damage to the wire ties than I saw when I did this to mine. Rereading the account... It's not clear if the broken valve ever had a wire tie under it. I think not, otherwise the break would have been noticed while trying to remove the shim on that valve. If I'm wrong on that, maybe the wire tie revealed the existing flaw.

Either way, y'all should be thankful it didn't pop off while it was running. I've seen what that can do to an aluminum head, and there wasn't much left of the piston. The good end of that head was was sawn off and used on another project...

With this being a mystery, are you planning to replace only the broken valve?

Not my bike, as its Steve's sons, so i am not positive, but I think we mentioned something about replacing the seals and rings since the head and jugs are off. Wouldnt be a bad idea IMO, but as i also said, its his sons, his sons money so that i suppose is up to him He and I were also very VERY thankfull it happened then rather than when someone was on it. Could have been disaster for both the motor AND the rider. :shock:

 

[Guest]

my crashed bike

that looks like a serious accident you had :-s - "how's the rider doin'?"

 

[Steve]

Hard to say without getting a real close look at the fracture zone.

You just knew I couldn't resist another chance to use the super macro function on my camera, didn't you?

These close enough?

It's hard to get light in there when the camera lens is almost touching the subject, so my LED flashlight is about the only choice.
The first two pictures are of the valve, the second two are of the stem.

.. It's not clear if the broken valve ever had a wire tie under it. I think not, otherwise the break would have been noticed while trying to remove the shim on that valve. If I'm wrong on that, maybe the wire tie revealed the existing flaw.

We had just moved the wire tie from the valve that broke and were going to the other valve in that cylinder. I can understand that sideways forces would tend to break the stem, but would not think that would happen at the hand cranking speeds used while trying to position the wire tie.

And, you are correct, this is NOT one of the valves involved in the red pipes. The red pipes were 1&4, this was #3.

.

 

[Nessism]

So do you think the bending load from the wire tie resulted in the valve head snapping off? I'm surprised the valve didn't just bend instead of breaking.

Next question is what are you going to do with the engine now? Replace the broken valve and reassemble or replace all the valves?

 

[tkent02]

So do you think the bending load from the wire tie resulted in the valve head snapping off? I'm surprised the valve didn't just bend instead of breaking.

Next question is what are you going to do with the engine now? Replace the broken valve and reassemble or replace all the valves?

That was my point. Something changed the metal into the hard and brittle state. No one else is breaking valve using the wire ties this way. In a few days when I get my bad valves out I will bend one up and send a picture of what they are supposed to do. I have seen pics of valves bent like pretzels, no break. Just because this cylinder didn't get red hot in the few seconds you ran it with the choke on, does not mean it hasn't ever gotten too hot and changed the way it was tempered. What makes things hard and brittle is to cool them quickly from a red hot condition, not sure how this may have happened inside the engine, but it might have. Running without the pipe perhaps?

 

[ALB80-850]

I'm getting better,slowly. Just had back surgery a month ago and need one more sometime in the middle of April and hopefully that will be it. I would like to be back to work by Memorial day weekend. Thanks for asking.

Andy

 

[Dogma]

You just knew I couldn't resist another chance to use the super macro function on my camera, didn't you?

.

Nice camera. It's still a hard break to figure out. It looks like some of the fracture was brittle, and some was fatigue failure. It's hard to be sure without turning it over under a magnifying glass, and maybe not even then. As was pointed out, the valve stem should be malleable, so the break should be a fatigue failure. I'm thinking that it only looks like a brittle fracture to the unaided eye. If the break took a long time to move across the stem, the telltale fatigue lines could be fine enough to look like a brittle failure.

I wish I was expert enough to be able to deduce more about what happened. I think it was about to break, and the side loading from the wire tie bent the valve over, then closing the valve pushed the head back towards center breaking it off. This could have been very quiet, where a brittle fracture could have made a fairly audible pop. Out of the zillions of cycles required for the break to move across the stem, you caught it at he very end. An amazing coincidence, if that's what really happened.

 

[Steve]

if it's a SLEEVE then it's a time-sert or similar
if it's a SPRING then it's a heli-coil or similar

Well, I finally got around to removing the excess from the spark plug.

It's not a spring.

.

 

[TheCafeKid]

Yeah i didnt see it cept for a second, but i was pretty sure it was one of those inserts. Actually better IMO than the Helicoil. We should try some high temp RVT when we put it back in, next time IT may stay in the head when the plug comes out.

 

[Nessism]

Yeah i didnt see it cept for a second, but i was pretty sure it was one of those inserts. Actually better IMO than the Helicoil. We should try some high temp RVT when we put it back in, next time IT may stay in the head when the plug comes out.

High strength Loctite would be more appropriate. Since the bushing is a solid piece the Loctite should stay where it needs to and not bleed through to the spark plug.

 

[hoyterb]

IMHO and over 40 yrs building SBC race motors some one f-up on the # 3 spark plug.When the tap was used to re thread the hole the valve was open.The tap hit the edge of the valve and cracked it. Not enough to break/bend.When you put the tie in it put just enough side load and it broke.You can see how the stress cracks are running straight across stem.You can also see a very small shiny place on the start of the break.Why didn't it break while running you ask.The springs don't have much pressure when the valve is on the seat.I would definitely check your valve springs for proper seat pressure. The only time the valve head has any load is when it is on the seat.Excess heat WILL weaken the valve springs.If you rev it up with weak springs the valve will not follow the cam lobe and may collide with a fast moving piston and in micro seconds seize the motor.Know what happens next !? [-o< If it was my engine I'd get another head.The valve guide on # 3 may be oblong from the tap hitting it.If you put another valve in and check side to side you will see it move more in the direction of the damage on the guide.

 

[TheCafeKid]

High strength Loctite would be more appropriate. Since the bushing is a solid piece the Loctite should stay where it needs to and not bleed through to the spark plug.

I was just stating what the directions on those state. High Temp RVT. Im guessing loctite might work too.

 

[first timer]

you will want to get either loctie red high temp or permatex red high tempature thread locker, any thing elese will not hold up, these are designed for spark plug inserts. These should hold everything in place but keep in mind to help keep the insert in the head even with the thread lock only remove the spark plugs when the head is cool to touch. Heat makes the thread locker soften up and more likely to break loss. Also use a anti seize on the plugs, the inserts like to bond with the plugs other wise.

you can get these inserts and thread locker usally at napa, might have to call a few but one of them should have the stuff you need.