Point well taken. I tend to be skeptical of HP claims. We have all been mislead on many occasions. The mags are full of HP claims, from headers to intakes and everywhere in between. Even the manufacturers have done it, and still do.
Good post Seattle, but I challenge anyone to produce laboratory proof that roughing the surface results in better performance.
The plane has turbulators for sure, but a typical good sized intake port runner is handling 15 m/s and giving a reynolds number up around 40000 which tells us it's fully turbulant = nil, zip, nada, laminar flow and any boundary layer would have to be modelled, because mathematiaclly it's too hard to postulate.
Of course a good piston can have turbulators too, lining up with the tips of the quench pads.
This is where you need to remember, "You can't race in a laboratory, or on a dyno".
I have never and probably will never be able to research anything in a lab. I will just have to rely on Smokey's and Vizards research as a guide, that, and my own observations.
I can tell you that most engines that I have seen with super smooth ports have had what appeared to be less than ideal low speed distribution problems. I can also tell you that I have seen less stagger jetting in engines with rough ports. This is backed up by inspecting engines during a teardown and freshen up.
Again this can fall into the same category as these other claims. We never had a wideband O2 sensor to nail down the, "close enough for most Holley".
It sure would be nice to duplicate some ports in acrylic and use a high speed camera, combined with wet flow, dry flow, and some smoke.
I can tell you that.
1 Then highest HP engines I have seen had smooth ports. But these engines are targeting max HP.
2 I have never seen a street or bracket engine that needed smooth ports.
3 Since the CNC port jobs have become commonplace, there are some seriously high HP machines out there with slightly rough ports. This could reflect the ability to properly size the port instead of the added roughness helping.
4 If the ports are sized properly for the size of the engine, and the intended application, the last remaining HP gains from mirror polishing will not be worth pursuing.
5 These are just my opinions based on my experience. If I were building you an engine, I would try to sell you on the combo that I am comfortable with. I would also stress the word COMBO. That word says it all.
