Not trying to stick my nose in here, but I have a valid question for the subject, I think. I have always been under the impression that hand porting (by a known good porter) was actually better than CNC porting. Am I out in left field with that? Just looking at a CNC ported head VS a hand ported one, the hand ported head has a much smoother finish. It seems that would lead to a head that flows better. Am I stupid?
Your thinking is real close to correct. (But never end a paragraph with, "Am I stupid? It's too hard to work around that without saying anything that makes it sound like I agree with "stupid", because I DON"T think you are stupid.) I don't believe it is the finish of the surface Rob, as much as it is the port shape. The CNC port is only as good as the the hand porter that formed it before it was programmed into the computer.
I think starting off with a pair of CNC heads and then finishing them off by hand, blending bowls,etc would be the best way to make power.
But i'm still confused on why you think a 365 cc indy head would be better than a 385.
Len from Mancini racings 63 Plymouth has the same motor as mine but his heads are 385 cc ones done by jeff at modern cylinder head and they got over 425 cfm out of theirs.Which makes me think with a new set of 385 cc heads my motor could make more power and get me where I want to be with ET & MPH.
In a previous life my sons and I were weldors. While working at a heavy equipment repair and construction outfit, the quality of our welds had a notable difference from those of other weldors. Soon we were hearing from those weldors, "Hey, you trying to make us look bad?".
Under our breath the return comment was always, "No, you're doing that all by yourself!"
Eventually the word came that my sons and I were to do the finish or cap weld passes so that the finished product would look better. That resulted in slower production and a less quality finished product. Why? We had to remove all the garbage from the fill passes in order to put a good weld on the surface.
What does that have to do with porting?
Hand blending a CNC port might be the easiest way to gain a "few cfm". (Or having your best weldors cover up some other weldor's junk will make it look a little better.) But what makes you think that the biggest CNC ported head is the best foundation for the most flow? (Or that junk weld fill passes are the best solution for quality finish welds?) Is 425 cfm all they are capable of? Maybe the CNC program is LIMITING them to 425 cfm because material has been removed during the machining that is required for greater flows. Why not 450 cfm? I have tested CNC ported heads on our flow bench. Never have they come up, on our bench, to the flows as advertised. We start with as-cast Edelbrock 440 RPM cylinder heads, hand port them, and they flow 348 cfm @ .700" lift. What does the CNC program get you? An "advertised" 320 something cfm?
Now the truth.
Can we start with an as-cast 572-13 head and make it flow 450 cfm?
I........DON'T.........KNOW! We've never had the opportunity to try.
There are some really good head porting shops out there. Are they better'n the guys in Challis? Most of the world thinks so...................
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