Also, If Tom at Super Six is not using a Diffuser to 'enhance' the exhaust flow like Stieg and Coy do, the numbers are identical on the exhaust. Well... except for the Super Six heads flowing more below .300" lift, 7 less at .400" and 1 cfm more at .500" and .600". And yes... I do have the open exhaust flow numbers for the Steig heads from a reliable source.
heads without exhaust seats won't flow that much non-diffused. Coy miller heads don't even flow that much non-diffused, and they have a welded exhaust seat with a wild angle cut on the exhaust valve. We tested enough heads to find out that you are only going to flow a certain number on the exhaust side without rewelding. I don't buy those flow numbers at 28" h20 on a 3.8" bore, not on a 1.55" exhaust valve, no way.
An SC specialist is just someone that's spent (wasted?) time and money trying stuff that didn't work. An SC motor is no different than any other motor. Yes, it has certain flaws, but when building a high power motor all areas will be inspected and improved no matter what motor it is. It's all the same.
wasted time and money on somthing that didn't work, or rather invested in a design that outperformed what is currently available. I'd like to disagree that headporting is all common knowledge, and techinques are all the same. Look at Dave Neibert's car, and his dyno results. Chris wise did the porting, but the exhaust ports were welded up like stiegemeiers. If this was all common easy stuff, why was stiegemeier the first to do it... 13 years after the release of the SC.
As far as cost, yea Stiegemeier and CMRE's aren't cheap. But first figure that there's about $1000 worth of hardware in each brand. High end valves, guides, springs, titanium retainers, and seals aren't cheap. So if you already have that much in, figure Coy Miller has to weld in an a new exhaust seat on every cylinder, that's time consuming. Stiegemeier has to weld up the roof and a few other places on each exhaust port. So figure that could cost atleast $500 from each place. Now you are left with porting, installing new stem seals, valve work, and flow testing, which covers the other $700 or so. Maybe you could get that $700 work done somewnere else for $400 - $500, but Coy and Stiegemeier have to charge a little more to help cover R&D and recoup the investment on the initial project. It's not like anyone is going to sell 1000 Super coupe heads.
bottom line is you get what you pay for. If you are trying to build a budget car and have the time to redo things, then do it yourself or go local. I'm sure there are a lot of shops that would you would be confident dropping heads off to have the exhaust ports welded and reshaped
But if you want to be the fastest, and to do things only once, you'll pay more for somthing that is proven and tested for any specific application (like SC's). I've seen enough guys with backyard head porting switch to stiegemeier's to prove that point.
Brian