The ultra-stiff Crane alloy-steel-body...
The ultra-stiff Crane alloy-steel-body hydraulic lifter was a key factor in the building of our 425-inch valvetrain. By having a very low collapse rate, these lifters ensure the motion input by the cam profile actually reached the valves.
For carburetion, Laz has a Cup Car carb builder that custom builds his highly functional carbs at a very nice price. The one built for our 425 was a custom piece with a booster design that had already established itself as optimal for this sort of application. Just as a reminder, the atomization produced by the booster/emulsion well/air bleed combo plays into our induction system's wet flow scenario. If the fuel droplets are too big, it counters most of the work we did refining the wet flow characteristics of the intake port. If the droplets are too small, too much fuel vaporizes in the intake manifold and cuts volumetric efficiency. Get things just right here, and it pays off. From previous testing, it has been established that booster selection and the appropriate detailing of a Holley HP 950 can, on a stroker motor such as ours, be worth 15 lb-ft and 15 hp.
The Rest Of The Gear We are now down to build details that relate to a dyno installation. Because it simplifies the dyno work, a Meziere electric water pump was used instead of a mechanical pump. These water pumps are typically good for 6-7 hp at 6,500 rpm, and as much as 12 hp at 8,000. For an exhaust system, dyno headers with a tuned secondary length were used. These headers had 1.75-inch primaries with an average length of 36 inches. These dumped into a secondary of 3.5 inches diameter, and a length of 14 inches from the end of the collector taper. Of the two, the secondary length is by far the most critical. Shorten this by 4 inches and the price can be a 20hp drop in output.
Dyno Time With our 425 on the dyno, expectations were running high. Eight degrees of initial timing proved to be a good starting point, and this fresh 425 Windsor lit off before the second revolution was even underway. It sounded good right from the start, and as soon as it had generated a little heat, it idled just fine at 825 rpm even before any carb idle adjustments had been made. After cycling the engine up and down from 1,000 to 2,500 rpm for about an hour, it was shut down and given a post break-in service that included an oil and filter change, and a head bolt torque check. The final phase of break-in involved cycling the engine from 2,500 to 4,000 for another 30 minutes.
By now, the engine was deemed ready for some exploratory pulls. The first was a 2,500-4,000 pull, and from this we learned that our 425 was making too much low-speed torque for the dyno to pull down much less than 2,900, where it was making close to 500 lb-ft. Since the mixture looked safe on the slightly rich side, runs were increased in rpm until we were seeing 6,000, where the motor was making a solid 590 hp.
 The more optimally the cam...  The more optimally the cam is spec'd, the more important it becomes to time it in correctly. The intake centerline on this big-inch Windsor was set to 103 degrees after TDC. |  Shown here are the retainers,...  Shown here are the retainers, springs, and valves used in the RHS heads. The COMP beehive springs, originally intended for big-block Chevy applications, delivered 150 pounds on the seat, and 390 pounds at full lift. |  With a higher off-the-seat...  With a higher off-the-seat ratio, the Crane Gold Race rockers proved a good choice for the 425 inches that had to be fed. With this higher opening ratio, the area under the curve was greater, thus allowing better cylinder filling and emptying. |