Quick question:

What kind of performance loss would you see from a broken or weak valve spring? Would it be drastic?
Also, could this possibly cause a loud knocking sound at higher RPM's, but not at idle??

Any input appreciated. Thanks!
-Ben

 

you'd have a dead hole, you'd know it

 

Yup, it would be drastic. It would manifest itself in other ways besides knocking noises.

If you have what sounds like a RPM-dependent knock that occurs at valve train speed as opposed to crank speed which is double the valve train speed, then it's probably a rolled / rolling cam lobe.

 

I'll check today to see if it is RPM dependent or if its the same frequency as the valvetrain. Hopefully this will give me a little better idea of the problem.

 

Also, if you hook a vacuum gauge up to the engine a broken valve spring will make the needle bounce up and down rapidly.

...been reading my ASE A1 study guides too much!