# attn Domantion **URL:** \ **Category:** PittSpeed Automotive\ **Created:** [October 28, 2006, 2:02pm UTC](https://forums.speedlife.net/t/attn-domantion/185885 "2006-10-28T14:02:45Z")\ **Posts on this page:** 1\ **Showing post:** 70
**Author:** ![Dominator](https://avatars.discourse-cdn.com/v4/letter/d/a4c791/32.png) [@Dominator](https://forums.speedlife.net/u/Dominator)\ **Post date:** [January 3, 2007, 5:39am UTC](https://forums.speedlife.net/t/attn-domantion/185885/70 "2007-01-03T05:39:33Z")
> [@OFFICIAL Buffalo Sabres Thread](https://forums.speedlife.net/t/official-buffalo-sabres-thread/25170/3792): > > I spend about 3-4 days doing a street/strip type port job on 3400 heads. If I “flow match” them on my flowbench, it was taking me 3 weeks to do this when I first started. Last time took me 4 more days. Now I don’t work 8 hours non stop as my wrists won’t take it. I also do more than port work. My flowmatch is 2% variance max between 6 ports. The flowbench I use has 1% repeatability, proven in magazines and my own testing so that leaves 1% for my error. I try to go as close as possible without chasing my tail past where I want the shape to be but I have got them as close as 1% max variance (.5% from the mean value). That is average for all values from .050 to .500 in .050 increments. While I do my best at each measurement, the casting difference between heads/cylinders makes it difficult to do that. Its interesting to note that if I turn the screw a little, I can usually get the values desired. To do a true graph of matching, you need to measure in tighter increments…say .010. > > I was told cnc can do some crazy % variance, like .005 or something. I don’t know so I won’t comment on that. I am not trying to say a human can beat a well programmed cnc machine because of all the variables. Popular engines for modding will get that sort of aftermarket attention because there is money to be made. CNC is faster for repeatability and from that stand point is far superior. You can’t really compare that with a custom hand porting though. Anyone on here that is so addament about flow bench testing has no experience with flow benches. They have no clue about the variences of eye sighting maniscuses of the vaccum tube, and the flow tube. There are variences with your dial indicator. What if you have it just a bit off angle. Basically they think they know, but they just don’t. I don’t know your process of porting but mine has alot of steps. I devide the runners up into about 4 or 5 areas. I’ll start with the bowl, and then do all the bowls. Then profile the valve guide boss on all of them. Then smooth the long radious. Then smooth the short side. Then gasket match. Then slim the pushrod guide bulge. I do them in small portions so that my overall varience is minimal. Some people just don’t understand how well you get to know the ports when you work with them so long. People that work with dolphins can tell them all apart. The all look the same to me. People that port heads can pick out minute variences and fix them. When the hell did CNC become a debate point? Just cause some dumbass brought is up as being an exellent alternative to hand porting (if you have the money) doesn’t mean anyone disagrees that its a great method. Come on newbies lets do some research before we post so we don’t look so foolish. --- _[View the full topic](https://forums.speedlife.net/t/attn-domantion/185885)._