Originally Posted by david73
will i gain any horses by changing from 993 heads to 487x heads on my .060/350 with .430 cam
A lot can depend on the condition of either set- if they are in the same shape, valve job-wise and such, the X heads will be worth a few HP over the 993.
But if the 993 were in top-notch shape and the X heads were worn out, the 993 would be better.
That said, neither will be all that, but I'd give the nod to the X's, all else being equal. The gains will be at the upper end of the powerband (the main difference AFAIK
, is the intake port volume), so you'll not be seeing it w/o running them at the track and charting the ET/speed.