[Streetwize]

I have one of the first set of Twisted Wedges and they were worked to flow ~250 @ .400 and 280 @.500 and they are on my 427W (also one of the first CHP kit motors). The TWs work exceptionally well with a power peak at around 5800 rpm (I limit the res-line to ~6200) with Custom Comp XE Hydraulic and a Ported Victor Jr. To get big improvements in power you need to see some pretty significant gains in the MId-Lift flows, the valve passes through 1/3 to 2/3 lift TWICE but through the peak only once and for a comparatively small number of degrees. If I were to do another set of heads I'd look at the Jegs/Kaases but in my case I'd have to upgrade the whole bottom end to a forged crank to really be comfortable with heads good for another 500-700rpm. I wanted my 427 smallblock to feel like what an all aluminum big block 427 would feel like, wall to wall torque in any gear with a decent but not statospheric RPM range.

Rule of thumb is you need 4.1cfm per HP per Cylinder, so I figured 280 is good for at least 520-540 potential HP (if you use enough cam and compression to get it) which is right at the limit of where I'd put a stock block anyway. To go to 300-310cfm heads I don't have enough short block to hold the extra power (and Heat) anyway. Remember this one was built when aftermarket blocks were only in our dreams

As for headers, 1 5/8" is too small IMO for the 427 especially if they are coupled to the 3" small block style headers. I run a 1 7/8" with a 3 1/2" collector, I do this for the same reason as the Vic jr and the 800cfm carb, low end and mid range torque can be borderline excessive with 427" in a lightweight car, by moving the torque peak up to the 4000-4200 range and it's essentially flat from 3000-5200, so it's right itn te fat part of the curve at your shift recovery points. So it depends what you want but if the .200 to .400 lift numbers aren't a big improvement over what you have and you're not running a big roller to take full advantage of the peak flows, you might not gain as much as you might think in terms of average torque (what you drive) or peak power. The header change alone might give you better overall bang for the buck than doing both the headers and the head swap IMHO.