I'm putting a 99 explorer 5.0 in my 69 mustang with a carb and am thinking about going to a e303 cam. I've heard I would need different springs. Can you guys let me know what all I would need to change if I go with this cam?
Depends on the extent of the mods you plan on doing? If it is going to stay pretty much stock, it wont really matter. I would use the stock valves in those stock heads as the power gains without more modifications, port work, intake change, headers, without other changes the gains are going to be very minimal either way.
Hope this does not burst your bubble but.
You would be better off to wait on doing it when you can go to some GT40 heads with an intake upgrade. My 2cents[/QUOTE]
I changed my springs on my Explorer GT40s, I didnt want to take any chances with valve float at upper RPM. The used stock Explorer springs are pretty weak, they even *looked* thinner than the springs on my E7 heads, I cant say for sure. I recommend the Trick Flow spring kit for Ford iron heads, and you can get rid of the heavy exhaust valve rotators too.