That blow up picture seems pretty crazy. I was also wondering about the guide size. Where you using stock 8mm guides or did you have a different size put in?

 

I just got the pistons back and thought that I would post the pictures and see what you guys have to say. I also noticed something odd about the valves if you look at the stems there is a definate line where the stem meets the head, I wouldn't think that a 1 piece forged valve would have a line like that. Well let me know what you guys think.

Piston 1


Piston 2


Piston 3 is screwed and doesn't pay to show you.

Piston 4


Piston 5


Piston 6


Piston 7


Piston 8


Intake valve


Exhaust valve


I talked to LPE and they said that the reliefs of the pistons were .210 in and .210 ex. So that seems like way plenty of relief.

I also talked to someone at Victory Valves and they thought it would be one of two things, PTV contact and it really didn't have to hit the piston if it was just hitting the carbon it would cause enough stress to cause a failure. Or valve to valve contact. We used 2.055 In and 1.60 ex, they thought that maybe the valves were hitting each other depending on overlap. Which I don't have the cam sheet so I didn't calculate the overlap.

Well what do you guys think?

 

The line you are seeing around the exhaust valve where the guides stop is from too little clearance of the valve guide. You may want to loosen up the exhaust guides a little bit if this is a track only motor. It may smoke a little more when cold but will be fine when it is up to operating temperature. I don't quite know what to say about Victory saying that the valves are touching at high RPM. If you have valves touching each other (especially with an inline valvetrain) you have got some real BIG problems.

 

You need to have your heads done correctly. That "line" on the valve is called galling, and it's metal transfer between the valve and the guide, lack of lubrication, improper stem clearance, vacuum leaks, and excessive back pressure can all be causes of this, but in your case it would look to me like iron guides with titanium valves is doing the damage that it always will. You cannot run Ti valves with iron guides. The heads need to have bronze guides installed and the valve job re-shot.

And there is a circular line in the valve pocket of the piston - PTV contact?

With a 2.055"/1.60" valve combo you should not be having any valve to valve contact issues.

 

There are definatly bronze valve guides in the heads, I can take a picture of that as well, but they are bronze. I just thought that it was odd for a one piece valve to have a line that you can feel between the stem and the head.
Also if you look closely at the stem just above the line you will see that the stem toward the head looks worn, I can see it better when I zoom in on the original photo, but it looks as though it was either wearing or the valve was somewhat mushrooming at that line. Not sure if I'm just seeing things or not.

 

That line of metal or mushrooming as you called it is the galling he is talking about. In this case it is caused by not enough clearance between the valve and the bronze guide. Any valve will do this with any type of guide if its too tight. It is just worse with Ti and iron guides. So with what you have shown here with these pictures it looks likely that the exhause valve binded up in the guide due to galling and got whacked by the piston.

 

In that one (small) picture of the head it sure looks like an iron false guide, and the color of the metal transfer looks like iron, bronze transfer will typically be more streaky, and less particulate. If it really does have bronze guides, then it is a clearance or other issue that was mentioned.

 

I see valve marks on the intake side of the pistons, anyone else?

 

I am not seeing it, sorry. Generally when there is PTV contact there is a well defined "eyebrow" on the piston which is easily distinguishable from the surrounding carbon deposits. It just doesn't look like it's there on these.

 

I see it too, looks like the valves are just barely kissing the pistons - or there was an over-rev and they hit a few times.

 

Thats what I'm seeing, not on the pistons but in the carbon.