Hi All
I know a guy who's got a 350 Olds engine in his jet boat that he wore out. I sold him a short block plus a set of bare #7 heads to replace it. He swapped over the valves, springs, pushrods from his old engine with #8 heads to this one. He took it out on the lake and it ran good for a couple hours, then it broke one of the steel rockers and bent the pushrod. He's trying to figure out what happened to prevent it from happening again. I have never seen this before. Anyone have any thoughts of what could have caused it? Are the springs/pushrods the same between a #7 and #8 heads? John

 

Did he reuse the timing gear?

 

I don't know, I'll check with him. The engine had low miles on a rebuild but I didn't have any paperwork on it. Since he said it ran good for a couple of hours I'm thinking whatever gave way must not have been critical prior to the failure. Which would fit if the timing gear came apart. The break runs along the bottom of the rocker.

 

Thank you Koda, I think you opened the door! After I texted him asking about the timing gear he told me the distributor was loose, so the timing gear still needs to be checked but it sounds like jumped timing likely caused the damage.

 

My 2 cents, have you thought about water in the cylinder [hydraulic lock] I would think if the timing chain jumped that much he would of had a running issue & possible more bent valves if this is a interference engine ?

 

I don't know. But I'll mention that to him as well. John

 

have him pull the spark plug from that cylinder if it is real white, that is more then likely the problem.

 

I ran across that only once on a fresh rebuild. A new valve guide moved up in the head. Sent the head back to the machine shop. Just one more thing to check.