Need a better cam

[1987cp]

if you're running stock valve springs, it will most likely valve float before the cam completely runs out. 5500 is the advertised top end for an E, and that sounds about right. Stock springs will probably float in the 5500-6000 range, and the stock rev limiter is 6250, so you're not getting past that anyway.

You EFI people ..... always assuming that everyone is permanently subject to the whims of the Great EEC-IV Engine Control Module .... :p

More seriously, though, around what RPM would brand-new stock Mustang springs go into valve float with a stock Mustang or Explorer cam?

[gadget73]

6250 with a stock HO cam is way outside it's power range, even if the valves weren't floating. I'd bet they'd give up before you hit that rpm though. 5500 is probably about all you'd get out of stock valve springs before they're just not enough. The cam has likely quit pulling by that point anyway.

I've had my car at 5200 with better than stock springs. It doesn't make power up there. All I got for my trouble was a blown header gasket and a lot of high rpm sounds until I upshifted. Explorer cam is pretty much done at 4800.

[CaptainKRM]

Same springs. They are awful.

TFS makes a spring kit that fits stock heads. It's cheap and a great upgrade for any mild aftermarket stick.

do you need to machine the head to run these springs? what about better lifters?

[OVERKILL]

do you need to machine the head to run these springs? what about better lifters?

Stock lifters are fine. No machine work necessary for those springs.