bigger is better:
After much discussion, it turned out that the C-454 test pushed us right on to the big stuff. The Edelbrock Vic Jr. is arguably the best intake you can get for a 4150 carb on a big-block, and even though we cut the plenum down to fit under the hood, the craftsmen at Wilson had worked their magic to get all the flow back, and then some. This is not to take anything away from the Wilson Vic Jr. because this was not a PURE back-to-back test. We had also added a larger carb to the mix to fit the C-454 intake. But when it was all done, if the C-454 was even in the game with power, it was now very clear that Bruiser needed some serious airflow, and even the ported Vic Jr. was strangling it. Chris had his gaze set on the Wilson CNC’d Edelbrock Super Victor on the bench, along with the custom Braswell Dominator that we borrowed from our buddy John Wilson. In a flash, we had it installed. At this point, none of us was done with the flat-tappet cam. We all knew it had a lot more in it if we could feed some air to it. After a few jetting changes, that great big intake and carb made 710 lbs-ft at 4,900 rpm and 810.4hp at 6,500 rpm! During the jetting exercises, we were able to pick it up to 715 lbs-ft and only lose 1hp at the top end. Now, how could this be? Big single-plane intakes are supposed to make a lot LESS torque, right? A good one doesn’t! Even down at 4,600 rpm where the tests began, we were up 25 lbs-ft and 22hp. Remember, driveability of big intakes and carbs is in the tune. This intake won’t fit under your L-88 hood, but there is no reason not to give your toy everything if you’re willing to change hoods or be a little sneaky!
By the way, once we established where peak torque was occurring, we started all later tests at 4,600 rpm. We saw no reason to hammer the engine at low rpm. The dyno holds the engine’s acceleration rate to 300 rpm per second, which is MUCH different than you experience in a car. If you dropped the hammer on Bruiser, I can guarantee that you would be through 3,000-4,000 rpm in about a nanosecond!
We blocked off two days to allow for swapping out all of the necessary pieces and dynoing them on the SAM engine dyno facility.
time to go hydraulic:
We were well over 800hp, and we hadn’t even broken a sweat yet! Next, it was time to detune it some, switch back to the intake that would fit under our hood and do testing with the hydraulic roller cam. This cam was selected to lower the rpm for peak horsepower. We weren’t sure what version of these motors Doug was going to pick for his final configuration, but my plan was to give him some rpm range past peak horsepower without encountering valve float.
We were able to swap the cam with little drama, due to the Jesel belt drive assembly. With the belt drive, there’s no need to touch the oil pan bolts; the cam slides right out without even removing the harmonic balancer! Degreeing it in is a cinch, too! The longest part of the swap was the need to change out all the valvesprings. This swap required much shorter pushrods, but we were prepared with another set of the beautiful Trend 7/16-inch x .165-inch wall units that we were using for all the combos. Crane had been very specific about doing everything possible to stabilize the valvetrain by reducing flex and unwanted motion if we ever expected to get any rpm out of a big-block Chevy with a serious hydraulic roller cam. These pushrods, along with the Jesel shaft rockers, were a vital part of the plan.
As soon as we fired up the hydraulic roller version, everyone was grinning. It had a great lope to it, but was very clean and responsive right off idle. We were now back to the Wilson-modified Edelbrock Vic Jr. and the HP 1000 Holley. Quick pulls verified jetting was still in line, so Chris shoved the SuperFlow throttle wide-open. The dyno was doing all it could to hold Bruiser back, but when it was all over, this “mildest” version posted 707 lbs-ft at 4,600 rpm and 760.5hp at 6,300 rpm. Peak torque might have been a little higher at lower rpm, but that’s where we started the pull. If you compare the hydraulic roller to the best solid flat/Vic Jr/4150 combo, you’ll see that peak horsepower was nearly identical, but the entire rpm range below that was much stronger with the hydraulic roller cam. It was consistently up 20-30+ lbs-ft. We also tested it to 6,800 rpm, to see if we would encounter any issues with severe valve float. What we found was that the Crane profile was very stable to the 6,500-6,700 rpm range, but by 6,800+ rpm, power was falling off rapidly … down approx 44hp from its peak.
Look at what happened when we compared the Barry Grant 850 Demon against the Holley HP 1000. Though throttle and venturi sizes are similar, the Holley boosted the curve all the way through. After adding one degree of timing, a little jetting and some more rpm, the Holley HP 1000 had our flat-tappet combo over 760hp.
If you are willing to upgrade to a hydraulic roller combo and spec it to stay under 6,500 rpm, you CAN make some serious horsepower and improve torque over a solid flat tappet. The advantage of the solid flat tappet is that you can rev it to the moon–literally, 7,500 rpm is no problem. IF you are going to gear the car to take advantage of that rpm, you could easily outrun the hydraulic roller combo. The increased low rpm power won’t mean much unless you operate at WOT in that range. By the time you drop the clutch and start pulling gears, the power above 5,500-6,500 will be very important, because you won’t be at 4,500 rpm very long. But again, for many folks, this is one sweet and dead reliable combo, and you aren’t likely to pull up beside much that will bother you. It is important here to remember the design constraints which Doug had given us: fierce at the track, driveable with 3.73 gears AND a double O/D T-56 Tranzilla six-speed. It also had to be reliable on the street and ultimately must fit under an L-88 hood.
