Having previously worked with them, I wouldn't use the STG VI heads if they were free. The Trick Flow is a far superior head. However, with the Trick Flow heads you would have to be careful about valve to cylinder wall clearance if your 426 has a 4.250" bore. Trick Flow doesn't recommend their heads with the 383's 4.250" bore.Thanks for the reply. Looking around, also looking at Mopar Stage VI and Trick Flow heads. Both ported and flow right at 330 @ .700. Going in 426, 4 spd @3400#
Hi,I am a new member and long long time mopar fan,my first post here.Can they make some power if you want to wrestle with them? Yes. They just are an early, crude cylinder head design. They need a tremendous amount of work to flow good. Short valves and large 3/8" diameter valve stems. Odd outside diameter brass valve guide. The spring pockets will fill up with oil above the valve stem seal if you don't do some special machining to get them to drain. Special intake gaskets and valley pans. 440 intakes or 3/4" spacer plates with 383/400 intakes on 383/400 engines and 3/4" spacer plates for 440 intakes on 440 engines. Not worth the hassle to me.
Yes the valve stems are the same length as the Edelbrock Victor heads. The heads you have are the same as the 78cc CNC version, yours are just not CNC'd. Poor quality control on the SpeedMaster heads. Mill the heads for sure to get them flat. Check the valve stem clearance. Definitely do a better valve job. There is a lot of flow to be gained by doing a performance valve job. Check to be sure that the rocker shaft saddles are the right height, location and the correct radius for the rocker shafts. I have seen SpeedMaster make the saddles so loose that the rocker shaft will move all around in the stand. I've had to re-machine the saddles or make custom spacers to locate the rocker shafts properly.