What is the life expectancy of valve springs on a stock 502 MPI? What are the symptoms of them getting worn? Is it just loss of power or does the engine misbehave in some other way?

I had the heads done on mine just as PM. It was still running fine, but everything I had read about 502's recomended new springs around 500 hours. That was 100 hours ago, still running perfect.

I'm pretty sure that the 502mpi's do not have the same valve spring problems that plague the HP500's. I rebuilt both of my 502 mpi's at 450 hours and both motors still had good valve springs....but I did replace them.

Thanks for the input. I only have 300 hours on the engine so it is still some time to go. What are the symptoms when they get worn?

I think that they work fine up until they break. Then you have some serious down time. I would not chance it.

So is 500hrs a good mark for PM/replacement on the 502?
I have 385hrs on mine.

Thanks for info,

i had carb hp 500's changed mine at 350hrs, not 1 broken spring, but i wouldnt chance it.

Most valve spring breakage is due to the motor being reved up before the oil temp comes up and, springs aren't ready to handle a load and get shocked.
With the 502 motors there was a tremendous amount of problems with the lifters failing causing a plethora of valve train problemos ! Never use any valve springs with any rust pitting , because that is where they will let go. If in any doubt, you will be way ahead to throw it out. The problem with motor stuff is easily dealt with when we realize really what happened and how and when.
Nothing worse than solving a puzzle and trying to make good on an IDIOTS mistake !!!