Broken Valve Spring on a 4.7
 

Just had a call from the garage that's looking at my truck. A valve spring has broken, thankfully without dropping the valve into the cylinder. What I need to know is, is this a common problem, and if not, could the failure be due whe some of the mods I've done, and finally recommendations to stop it happening again.

Mine is a 2000 4.7 with about 110k on the clock. A couple of years ago I had a set of KRC's 212x cams fitted, new followers were of course used but no other valvetrain items were changed (old springs put back in). As I understand it from the info supplied (and from experience driving it), these cams (when used with a 04 onwards manifold) make a very nice improvement across the whole rev range. But they certainly wouldn't be classed as a Race cam. I don't drive it that often and rarely rev it right out (too many speed cameras here in England!).

Do you think that the cams caused the breakage, and if so should all the springs be replaced? The garage were undecided as whether they all should be replace ALL the springs or just the broken one. If its a whole set, should I look for uprated replacements (if they exist), or go for original?

Thanks for any info.

Broken valve springs do happen on the 4.7, usually if it's been run very fast. If you've changed the cam profile then you should be looking at different springs.

Thanks for the reply. I agree that I think all the springs should be replaced but do you think uprated springs are necessary? This is still a "Road" cam grind, I don't know the spec but I'd be surprised if they are much lumpier than stock HO cams.
I think the mistake was not changing the valves along with the lifters. At that point the engine had done about 80k miles. Recently. I've been driving the truck very little, with sometimes a couple of months going between drives, would this have anything to do the failure?

Thanks for any further info you can provide.

If one failed there is a good chance another one is about to. Road cam or not, check with the manufacturer.