Contour Enthusiasts Group Archives Forums Modifications Duratec Performance Port and MAYBE polish II...the inside story...

Go here ,
www.drp.4t.com/head_tech.html

Great stuff Terry! Check this out, www.theoldone.com This site is a gold mine of tech info. Larry is a true pioneer in the auto field as well as others!

My head hurts after skimming that, but two paragraphs jumped out at me:

I think I've referenced the 'polish' part before..and as for 'open up' the ports re pinned/removed secondries etc..as you can see 'velocity' & cylinder filling are of prime importance re Weslake of England..!!!!need we say more!

good stuff terry!

though I would like to add a bit of commentary, for some of the folks out there

You need to remember, that things are all about balance, and intake ports (and exhaust ports) are no different in this regard. You need to determine what the ports you are considering need. Are they large enough? how is the port velicity? how much flow loss am I getting here?
Sometimes larger ports will help, sometimes they won't. An example, if you have a port that is perfectly balanced between it velocity profile and its flow volume, then larger ports will simply kill flow velocity, and reduce top-end power (maybe pick up a bit of low-end, but not always on that either) BUT if you have a port that has good velocity, but is actually restrictive to flow, then opening up the port a bit will probably increase flow w/ little to no decrease in velocity (or in rare cases my increase velocity)

It all comes down to the old adage, "measure twice, cut once" make sure you know what you are doing before you try to do somehting (unless you are experimenting, and can afford to screw up a few times)

It's all about balance. Look at everything as a system, and treat it as such.

I thought everyone knew that "some" amount of roughness was necesary to interupt the boundry layer to increase flow. The thing that causes it is that the boundry layer is more or less static (ie not moving) and you get huge "shear" along the edges where the fast moving gas trips over/rips away from the stationary gas. By introuducing very small amounts of controlled turbulence you essentially add teeny weeny air ball bearings for the incoming flow to slip against. I've seen the same principle used on the hulls of boats to limit drag (actually used air pumped along the hull). Also that is why golf balls have dimples, and air plane wings have little ridges on them.

The trick is that is takes damn near a Cray super computer to figure out when the turbulence is just enough to help and not slowing things down worse than they were to begin with. The engineering of a simple golf ball is really probably a cumulative effort of 1000's and 1000's of man hours of effort, and if anyone tried to dimple something to improve it's flow they would probably need a CNC machine, a flow bench and lots and lots of spare parts to figure out by trial and error what helped and what hurt.

(Disclaimer: Okay, so I got a C in my fluid dynamics class, and haven't used any of the knowledge in over 10 years - so take it with a grain of salt)

I prefer the mirror polish but not only from a performance standpoint, but a maintenance point of view. The smoother the metal the more difficult it is for gunk (not the best word choice, but it really fit here lol) to build up and attach. This gunk can build up and restrict flow, so its a matter of preventative maintenance. Just remember, no matter how smooth your ports are they will eventually "gunk" up, smoother just doesn't "gunk" up as fast in my experience.

Learn somthin' new every day

ttt...for the 'secondaries'...experts!!! :rolleyes:

Heh heh heh heh.. Wider is better!!!! :p At least thats what Pontiac says. *Note sarcasem*