SB

iTrader: (1)

Why is it always better ? Makes no sense.

Full Force

iTrader: (5)

Supposedly you can massage the right places better by hand, I have read many times people pick up cfm after a hand port over cnc, that being said people have to know what they are doing also...

SB

iTrader: (1)

I understand, which you know, and I know you understand.

It's just too blanket of a statement for me not to say something about...that's all..

CNC is a copy of whom ever did it and forwhat application. Same as a hand port, because that is what it as.

No two people are a like and thus no two porters are all alike.

Full Force

iTrader: (5)

I know what you mean, just when I was talking to people last year, many said gains are to be made by hand finish, it was explained why but cannot remember actual details..

getrdunn

iTrader: (7)

That's why we call them professionals. It's what they do and in many cases all they do. I just like the fact that in many cases a good hand porter can take less material than that of a cnc head resulting in flowing more cfm while gaining port velocity at the same time. And all can be done build specific. Plus I'd rather put money in a US hard working knowledgeable mans pocket than that of corporations.

Back to OT question my answer would have to be all depends on build but would favor a cnc head over a non cnc head if I was chasing HP and funds weren't limited.

14 apache

iTrader: (1)

Don't forget when you waste a set of heads because it drops a valve ask how long the head porter will need to duplicate your port job and will it have the same power as it did before? I will go cnc every time unless your pro stock racing or nascar and most of them start with a cnc head.

adk61

iTrader: (5)

this statement is just not true, an engine is a pump for the argument sake, and the better a head functions in terms of flow, the more efficient the "pump potential" is. blower or not

MILD THUNDER

iTrader: (3)

^^^ it's true. They proved that decades ago when doing all the blower development . Swapping out a poorly flowing head for a better flowing head, power skyrocketed, and boost plummeted . If anything, I believe the gains are even more beneficial from a high flowing head with a blower than with NA in some cases.

imo, the cnc vs non cnc, is that it really should be application specific . If a head porter knows that the engine will be lift limited, like most pleasure marine engines, maybe going after the best flow numbers from. 700 and up aren't the key. Maybe he would focus on the valve job, throat, and chamber to maximize flow in the mid to peak lift area. But if it's a max effort 800 lift high rpm deal, maybe he will focus on modifying the port to flow better up there. Anyone can hog out a port and make a big cfm number on a bench, but that doesn't mean the engine will be a hero.

14apache makes a good point. Having a custom set of hand ported heads, and you smoke one, a replacement may not able to be had in a timely fashion

port size is important, but so is cam lift, cam timing, and valve size , relative to how an engine runs at low speeds. Big valves and big lift amplify reversion. Going from a 250/260 cam with 650 lift and a 2.25 valve, to a 250/260 cam with .750 lift and 2.325 valve, you're not gonna get that same idle /low speed manners .

getrdunn

iTrader: (7)

I think it must be an old myth because I recall hearing the same thing many years ago and believed until I began spending more time with real world experience and results from back to back dyno testing. I was fortunate and had the benefits of living less than 3 miles from more power racing spending endless hours learning. Some late nights chasing power but time well spent. I miss those days.

SB

iTrader: (1)

How is it that the new Gen small block hemi's and small block LS's can be 900-1000hp with SC's ? Heads !
Take the same cid, 1980's cyl heads, and same modern SC's...think that HP will happen ? No way.