A few days ago I had a discussion with Dave at SD Performance, about 4X vs 6X heads. In stock form the 6X head has a few advantages, better exhaust port (double pass down both sides of the valve guide), and the intake port has some minor advantages as well, something about the floor and short turn, etc?
I do agree that any differences quickly disappear with correct porting, but as cast I'll take the 6X heads over the 4X every time.
The 6X-4 head also offers another advantage of having a smaller chamber. The vast majority of the castings I've prepared here have 91-92 cc chambers before milling. A few have been down around 89cc, and few up around 96cc. Most 4X heads are at least 98cc or larger.......Cliff
__________________
If you can read this, thank a teacher. If you can read this in English, thank a Veteran!
https://cliffshighperformance.com/
73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile),
|