Broken valve spring?

I have had a couple of the BIG camed 348 engines where the driver missed a shift and floated the valves. Never had bent valves but lost the lobe of the cam. Needed new follower and the lobe welded but leakdown showed no valve or cylinder problems.
Leak down test will answer your questions.

Dave

 

That's not good, Dave. As Mr. Helms says, the leakdown test will identify and pinpoint precisely where the problem is. Likely in the valve train. It doesn't sound catastrophic (bottom end). Do the test, then drop the subframe and pull that head. Not likely a valve spring problem if you've lost compression, perhaps a keeper or retainer problem. Possible "money shift"? That could tag the valve(s) and bend the valve stem enough to keep it open and lose compression.

 

I hope you did not lose the cylinder or damage the piston. A compression/leak down should be able to tell where loss of compression is coming from. Good luck!

 

I have had valve springs break in a few of them. Never bent a valve. It has double springs so if an inner you probably will not even notice. If an outer it will float at a very low RPM but will just feel a little flat. No other symptom was ever noticed.


I am afraid it is something else.

 

I had a similar problem 92 348 driving at high speeds pushed in electrode #1 cyl.I did both leak down & comp test. #1cyl=0comp,#2cyl=100,#3=0,#4=150/175,#5=175,#6=125/130,#7=115/125#8=150.Going to remove the engine over the winter and do a service at the same time. Any help or ideas on the problem. Also inspected all piston with elescope no damage, just lots of carbon.

Thanks

 

That motor doesn't need a service, it needs an overhaul.