340 X head max spring tolerance?

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stock head with stock springs and valve guide...probably not much over .500
 
the guy I got them from said he had a "lumpy" cam with these heads, but I want to ere on the side of caution.

If I take it in, get the valve re-done and ported, maybe through some new springs in where I know I am good to .600" Should be decent for a few builds before i go aluminum?

how much cost should I be looking at for this work?
 
The springs aren't the only thing that affects how much lift a head can tolerate. The biggest factor is retainer to guide interference. To run a .600 lift cam you'll need to have the valve guides cut down and probably have the spring base cut for more spring installed height.

Your gonna spend some big money porting them and getting them machined to accept .600 lift. Plus the cost of all the parts. You'd be better off buying a new set of RHS heads (or Eddy's) and sell your X heads to someone that needs X heads, IMO.
 
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