"We'd be happy with 480 hp on motor, any more we'd consider it a gift from the racing gods," is what we thought as we travelled up Interstate 15 with our Rapp Racing small-block securely strapped in the back of our diesel. Considering the list of off-the-shelf parts, mild hydraulic-roller cam, unported heads, and 91 octane pump gas; 475-485 hp at around 6,000 rpm was our guess for this latest stroker recipe—enough to put our lightweight early Nova project car within striking distance to our quarter-mile goal of 10.00. With nitrous oxide, we'll surely be in the single digit zone.
Besides breaking it in and gauging the power output, putting it on the engine dyno allowed us to test a couple different carburetors; a pair of Black Diamond Q-Series carburetors from Quick Fuel Technology, a 750-cfm (PN BDQ-750) and 950-cfm (PN BDQ-950) version. The idea was the larger carb would work better on spray and with a loose enough converter, could also work on the street (if we wanted to pay for the extra fuel). Of course, many gearhead thoughts racked our brain on the way to Westech Performance group in Mira Loma, CA, but mainly, we anxiously looked forward to hearing the roar of power through the pipes once the NOS Big Shot plate was activated.
The combination is a Mark Rapp-built 385ci small-block with 6-inch Scat rods, 10.65:1 compression from Mahle PowerPak pistons, a hydraulic roller from COMP Cams with 230/236 at 0.050, Summit Racing 200cc aluminum heads, RHS single plane intake, Moroso oiling system, Hooker 1-3/4 headers, Quick Fuel Technology carb, and a Pertronix ignition. For somewhere between $8,000 and $10,000 in parts, depending on your exact combination, you can order these components from Summit Racing. For our build, we set out to see what kind of power can be had with this off-the-shelf combo, and we think most would be surprised, we certainly were.
Before the dyno testing at Westech Performance Group, we actually ran the engine on this nicely built run stand at Rapp Racing in Huntington Beach, California. The snappy revs sounded very promising, and probably the best part … no leaks!
At Westech, Steve Brule’ and Troy Goldie unloaded our 385ci and hooked it to the 902 SuperFlow dyno.
We learned since we’re running a roller cam, the break-in procedure is not as delicately specific as flat-tappet cam is.
We like to run a FilterMag on our oil filters, especially on a new engine. he high-strength magnet holds finite bits of metal that would otherwise be circulating in your oil system. The filter is Moroso's Race Oil Filter (PN MOR-22460). It has a 27-micron filter capability, anti-drainback valve, and a high burst strength.
Cool details like this Lokar Performance locking dipstick (PN ED-5001) makes this engine look sweet and the black anodize matches the theme.
After Brulé set the dyno to modulate the revs for a few minutes, the 385ci was ready. The first pull of the morning, at a conservative 31-degrees of timing, netted 474 hp and 475 lb-ft of torque at 5,100 rpm, very nice numbers for the initial pull. We still had timing, jetting, new oil, and a bigger carb to try before the day was through.
Westech’s SuperFlow 902 is set up with a powerful Aeromotive fuel system that can handle big horsepower. This pump setup is more than enough to handle our power output, even with the nitrous at full spray.
A few more pulls closer to 6,000 rpm and our little stroker was pumping 491 hp and 489 lb-ft on 91 octane; the timing and jetting was still untouched.
Changing the timing from 31 to 35-degrees pushed our dyno numbers over the 500 mark. At this point, we were ecstatic since we weren’t done tweaking it. The TCI Rattler and TCI Timing pointer made setting timing a breeze.
Once the engine had a couple pulls under its belt, Steve changed the oil and replaced it with fresh high-zinc 10W-30 from Lucas Oil Products. This change alone gave us close to five more horsepower and torque.
The Black Diamond Q-Series Quick Fuel carburetor ran pretty good out of the box, but Brule felt it was a bit too rich and could use a downsize in jetting.
We pulled out the .074 jets in the primaries and screwed in some .072 jets and took the rear down to .076 from .080. We also went with a 10.5 powervalve to help smooth throttle tip-in.
We also noticed the QFT carbs come with jet extensions in the rear float bowl; these ensure your carb doesn’t get fuel starved during hard launches.
With the 750-cfm carb, 35-degrees of timing, and fresh oil, our 385ci belted out 506 hp and 495 lb-ft of torque. From here, we decided to try the larger 950-cfm carburetor.
The 950-cfm QFT carb (PN BDQ-950) features a larger throttle bore and venturis for greater airflow. We were curious to see how the 950 performed at the low rpm, since we were told it may be too large for cruising. At this point we added a degree of timing as well, for a total of 36-degrees.
With a fresh tank of 91 octane and the engine well broken-in, Brulé made a couple more pulls with the 950-cfm piece and glimpsed a stellar “518.9hp and 496.7 lb-ft” flash on the screen. We even observed a pretty smooth low rpm throttle tip-in with the bigger carburetor, as well.
A full, 10-pound nitrous bottle was hooked up to our potent powerplant. Brule’ made sure to keep our pressure at an ideal 950 psi.
The nitrous system we chose is Nitrous Oxide System’s Big Shot Plate Kit (PN 02101NOS). This is a simple, effective power adder that can increase power output (to the wheels) up to 300 hp!
This kit comes with high-flow "Cheater" solenoids, 88-hole spray bar, and a 10-pound bottle with brackets.
With 100 octane Rocket Brand racing fuel in the tank, and two degrees of timing taken out, we unleashed the laughing gas, making sure to purge the air out at the solenoid before making the final pulls. We only plan to run the base “190hp” tune on this engine (0.073 nitrous jet with a 0.067 fuel jet) since our piston’s ring lands are fairly close to the top of the crown and too much heat in the chamber could potentially lead to meltdown if you’re not careful.
With a mighty roar, the 385ci tossed flames out of the collectors and we saw the power output spike well over 700 hp, and that was way before redline. It appeared we shocked the dyno brake on this pull too. After a few adjustments to the dyno, Brule’ made additional pulls on the sauce, all in the 730 hp range, which is more than enough power to get our project running in the nines … and possibly quicker after the chassis is sorted out.
With 519 hp on pump gas and more than 730 hp on nitrous, we were ravenous to get the engine into our early Nova. Back at the Source Interlink Tech Center in Irvine, California, the real thrash begins. In the next few issues we plan to show off assembly of the interior and engine bay, it won’t be long now until we’re doing burnouts and busting wheelies.
Dyno Results Naturally Aspirated
Fuel: Pump gas, 91 octane
Peak horsepower & torque: 518/496
Average horsepower & torque: 409/471
Dyno Results on Nitrous Oxide
Fuel: Rocket Brand, 100 octane
Peak horsepower & torque: 734/740
Average horsepower & torque: 535/481
Plate Jetting: 73 nitrous jet, 67 fuel jet