What's wrong with this picture? Part 2

[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.