Valve Springs

[Frogger]

How much lift can you run on stock valve springs in a FE motor ?

[DuckRyder]

Short of installing a cam and checking for coil bind an answer would be difficult. You also have to make sure the spring retainer or rotator is not going to hit the valve guide.

I would STRONGLY advise installing the correct valve springs and retainers for the cam you are using as there is more to it than simply can they achieve the lift without bind.

Modern cams in most cases (even mild ones) have much quicker rates of lift than the factory cam and with used stock springs you are probably going to be floating valves at 3500-4000 RPM.

[My427stang]

Although I agree 100% with the Duck that you need to check. A good rule of thumb is .500 lift.

Anything above that you are almost sure to have issues, and most every modern cam will be slightly above that.

[Frogger]

I was just curious because some of the RV cams I've seen are over .500

[390F100]

What is the true definition of an "RV" cam?

[DuckRyder]

What is the true definition of an "RV" cam?

It should mean a fairly mild high torque cam (IE suitable for a heavy RV). I reality it is an over used term that really doesn't mean much.

[willowbilly3]

Any cam manufacturer should be able to tell you if their cam will work on stock springs

[My427stang]

I would say that "any cam manufacturer can tell you their spring requirement"

Then you need to go see what your springs actually are, 10,20, or 30 yr old springs surely wont have the pressures new ones will, and the cam guy sure doesnt know what you have for springs.

The easiest thing is to measure installed height and buy the right springs and just swap. 50-75 bucks for peace of mind, or drop a valve and lunch a motor

[Frogger]

I would say that "any cam manufacturer can tell you their spring requirement"

Then you need to go see what your springs actually are, 10,20, or 30 yr old springs surely wont have the pressures new ones will, and the cam guy sure doesnt know what you have for springs.

The easiest thing is to measure installed height and buy the right springs and just swap. 50-75 bucks for peace of mind, or drop a valve and lunch a motor

New Valve springs are on the way, although the heads have just been reworked with new stock springs. I'm opting for a set rated for up to .600 lift just to be on the safe side. These are suppose to be as big as you can go without machine work.

[My427stang]

First good on ya

Second, are they matched to the pressure requirements for the cam?