[SVTCobra347]

If I'm planning on porting anyway, would I need to spend the cash on GT-40 X's or can I save a little and just get the Y's?

are there any really big differences?

I'm planning to gasket match the intake side at the least, and probably knock a little material off to up the compression. Yes I know pistons are a better way to do this but I already have SRP flattops.

 

[Klortho]

the 40x heads are supposed to flow better than the Y's

 

[Saleen302]

Y
Intake port volume 160cc
exhaust port volume 53cc

X
Intake port volume 178cc
exhaust port volume 62cc


Both use 1.94/1.54 valves & both have a good amount of room for porting. Just depends how much work you plan on doing to them.