I have a 700 horse 6-pak engine. They work great only if you know what your doing and how to modify the manifold. The last time we dynod my 535 we spent the afternoon testing manifolds. We found that a heavy worked M1 with a dominator made the most power, the dominator only made 3 horse more than a 950 and was 5 down on torque. The dominator and the 950 where both Quickfuel carbs. We tested a Weiand tunnel ram with duel 750 Edelbrocks, it only made 8 horse more than the 6-pak and torque was real close also. We ran a cross ram and was not inpressed at all. The 535 with the 6-pak made 698 horse and with the single four dominator it went 730. The 6-pak runs out of steam around 6500rpm, but then again my engine is a big cube motor with Edelbrock RPM heads so the screaming high rpms aren't nessasary. Just my