Dropped Rave Valve

[69DartGT]

We were riding our 2 96 GTX's Saturday and my son noticed he lost power in his. We pulled over and I checked the raves and noticed oil coming out of the Mag Cylinder one. I pulled the cap and the rave was pulled out of the piston. So we decided to head back and we were just about back idling in the channel and the rave dropped into the cylinder, not a good sound to hear. So I don't know if the rave was loose to begin with and rattling around pulled it out of the piston then finally breaking when it was free floating on the way back. Any thoughts on this? Thanks Scott.

 

[mikidymac]

I would say age. Here is no mechanical stress that would cause them to break.

 

[69DartGT]

Are the newer style that are slotted supposed to be less prone to breaking?

 

[mikidymac]

No, they just prevent them from sticking. Some engines would get stuck at 4,500 rpm and the slotted ones would help that, other engines of the exact same year had no issues.

 

[etemplet]

I suspect the valve clearance was pretty tight to begin with and the rattling around cause it to wear and drop a little further contacting the piston. I'd presume the top part of the valve broke after it contacted the piston. Gotta remember idle is 2800rpm so it's bouncing around quite a bit and a 5 minute ride is close to 15,000 times. Check to see of the piston isn't .25mm over standard. You can get away with not cutting the raves when boring to that size but you lose clearance. Get those chunks out of the engine. You can do the cylinders with the engine in the ski. Good Luck !!

 

[69DartGT]

That is my theory too, that the rave was worn and when it came out of the piston and rattled around it aloud it to drop just a little farther and
made contact with the piston. It has never been bored, this was an untouched motor that just turned 200 hrs on Saturday.
It really sucks because this is one really nice clean original GTX. But I am going to go .50 over on the cylinders and move on.
Thanks again for your time.