CNC Benefits?

[metal_man_xl]

Hey guys, just curious on the benefits of CNC machined combustion chamber on a set of new heads..a set of trick flows for example. Is it worth the extra couple hundred bucks? How much more power is really squeezed out because of it? Thanks

[VileZambonie]

Less valve shrouding and better designed combustion chamber = better breathability and more complete combustion.

Is it worth it? That depends on whether or not your engine has all of the other upgrades to make them work to the best of their ability. Slapping them on a stock engine isn't the best $ spent.

[metal_man_xl]

What about max valve lift limits? I really don't know much about cam specs, but i don't think i would need anything over .480". Would it be a better investment to go with the .540" max lift heads in case somewhere down the road i get a higher lifting cam?

[eventhorizon66]

Retainer to valve guide, rocker arm to valve spring, rocker arm slot to rocker arm stud are examples of clearances that should always be checked with the cam you plan to use, then determine whether machining/different parts are necessary.  But most aftermarket heads are not indicating limitations based on any of these clearances when they specify max lift.  They are giving you the recommended max lift of the springs they come with.  When aftermarket cylinder heads come assembled they typically offer two different springs you can choose from - the lower rate/lower max lift springs are intended for flat tappet hydraulic cams, the higher rate/higher max lift springs are for flat tappet solid and hydraulic roller cams.  Valve springs should always be selected based on the cam (type, lift, rpm range) you are going to use now, not down the road.    Always check with the manufacturer of your cam to determine whether the springs are appropriate.  You don't necessariy have to call them, just browse through their catalog (they'll typically have a spring recommendation for each cam) and compare the springs you intend to use with the springs they recommend in terms of spring rate, seat pressure, installed height, coil bind, etc.

[camdenoilchange]

assuming intake, fuel, and exhaust were matched appropriately.... can anyone tell us an approximate hp or torque gain from a quality port and polish job? and possible an average price of the job? i'm curious as well.

[VileZambonie]

Cylinder head porting is something I would never pay someone to do. You can easily do it yourself. It's time consuming and to pay someone $75 an hour to do it seems like a waste of $ to me. You may gain nothing if it's not done correctly. The idea is to have tight radius, velocity increase, and better VE. Port alignment will help also. As far as an HP gain only the dyno can tell you that.