HOT ROD Rescue: Carb, Fuel, and Spark Tweaks for an Early Nova
The Rescue So Far
Rejuvenated thanks to Comp Cams, Brodix, Fel-Pro, Holley, Cloyes, MSD, The Carb Shop, and ARP, the 350 drops back into the Nova.
When Rollings Automotive checked out Sean Price's 1965 Nova 350 small-block, it was dead upstairs, held back by a weird cam grind, valvetrain issues, crappy early 1990s TBI iron heads, a messed-up carb, and damaged spark-plug wires. We replaced the cam with a Comp Cams Xtreme Energy XR294H-10 hydraulic roller and Cloyes True-Roller timing set (Oct. 2016 issue), then trash-canned the heads for Brodix Race-Rite 200 aluminum heads and Brodix's high-rise dual-plane intake (Nov. 2016). This month, we'll get the carb and ignition up to snuff, sort out some chassis integration issues, and put the Nova back on the chassis dyno.
The Fix: Fuel
Neither of Price's two carbs-an 850 double-pumper (left) and a 750 Street HP (right)-responded to normal dyno tuning.
Price was running an early Holley 850-cfm double-pumper carb (PN 0-4781-2), but there was what seemed to be a 750-cfm Holley Street HP double-pumper (PN 0-82751) in the trunk. Neither responded to tuning during the original Westech dyno runs, with both down about 20 wheel horsepower (whp) from the best 260-whp baseline garnered with a known-good, 750-cfm shop carb.
To sort out Price's carbs, we brought in the experts at The Carb Shop, which specializes in everything from straight restorations to full-competition racing carburetors. Based on the Nova's engine size, mods, and intended use, The Carb Shop's Randy Robinson chose the 750 as the basis for a “Stage 2” blueprint.
Price's 750 carb was the best fit for his 350, but its mismatched parts needed a ton of work at The Carb Shop to get it into fighting trim.
Normally, Stage 2 includes a full refurbishment, truing up all machined surfaces, and custom calibration including jets, power valves, accelerator pump cams, and shooters, plus “secret” internal mods as needed to include idle and high-speed air-bleed changes and PVCR alterations. The goal is a consistent, flat fuel curve from off idle to the top end and is what separates The Carb Shop's services from simple dial-in tuning.
To forestall possible baseplate-to-metering block contact (which can cause sealing issues and vacuum leaks) as well as ease on-engine float bowl and metering-block removal for quick jet changes, The Carb Shop mills the baseplate vacuum-boss surfaces about 0.030 inch, just enough to “erase” the red marks in this photo. Bretzing: “We also true up all machined surfaces on the main body.”
Price had said the 750 never seemed to run right. No kidding. Turns out, only its main body (with its identifying Street HP List number) was “correct” for the series. Everything else was cobbled together from several different, incompatible carbs-plus, the basic calibration was plain out to lunch. The Carb Shop's OJ Bretzing found no primary-side power valve (PV) installed. Over-rich primary-side main jets, plus a huge 50cc primary-side accelerator pump, had been installed to try to compensate for the missing PV. “Never block the PV on a street-driven car,” Bretzing explains. “It's needed for driveability. Without one, if we found the right main jet for WOT [wide-open throttle], part-throttle sucks. If you use the right main jet for part throttle, WOT suffers.” Also needed was a new metering block and throttle blades.
Someone had installed a big 50cc accelerator pump on the primary side, probably to crutch the missing power valve (PV). With the proper PV installed, it would supply too much fuel on WOT transition. Note the thicker 50cc pump diaphragm housing (A) compared to the thin 30cc part (B)-a “50cc pump arm” only pumps 50cc with the thick unit plus a brown pump cam.
CARBURETOR CALIBRATION
In addition to these listed values, The Carb Shop also performed undisclosed proprietary air-bleed and PVCR modifications.
Primary
Secondary
Main jets
No. 72
No. 82*
Pump cam
Pink
Brown
Pump nozzle
0.031″
0.037″
Power valve
4.5
None
Needle & seat
0.120″ Viton (both sides)
*Leaned to No. 77 during dyno-testing.
Back at Rollings, the carb was installed atop a Summit phenolic 1-inch-tall open spacer, added for more top-end breathing. Other fuel/air enhancements included a Holley 110-gph high-perf mechanical fuel pump, a better throttle-cable bracket, a raised air-cleaner base, and PCV valve provisions.
To keep up with the 350's now-higher power potential, Rollings installed a Holley 110-gph high-perf pump actuated by a Howards Cams ultralight, carbon-fiber pushrod. On the motor, the pump's lower housing was reclocked for clearance and better hose routing, with the plumbing upgraded using Phenix elbows and hose fittings installed on Price's existing pump-to-carb hose.
The Fix: Spark
Price already had an MSD-6 ignition box, Blaster coil, and MSD billet distributor, but several wires and boots were burned or cracked, and the distributor cap and rotor had seen better days. They were upgraded with new MSD parts, including a universal wire set Rollings custom-tailored for the installation.
For valve-cover clearance, MSD's Blaster coil was relocated from its original firewall mounting position (arrows) to the inner fender wall. For cleaner coil wire routing, Rollings replaced the universal wire set's 90-degree coil terminal boot with a separately available straight MSD boot. MSD also supplied a new distributor cap and coil. Spark-plug wire routing is tight with the early Nova's high shock towers, Price's 1¾-inch primary-tube headers, and the Brodix heads' angled spark plugs. Rollings' crew tailored a universal MSD 8.5mm Super Conductor wire set, Pro-Heat Guard, and wire separators plus custom-made standoff brackets to cleanly route the plug wires under-header along the oil-pan rails.
The Fix: Front Drives
Cloyes' Quick Button Two-Piece Timing Cover, with its adjustable cam stop, is said to clear “most” short water pumps, but not the generic short pump on Price's 350. Rollings used water-pump spacers to gain the necessary clearance, then shimmed and machined the crank and alternator pulleys to restore proper drivebelt alignment.
Price's generic short-leg, parts-store water pump hit the beefy Cloyes front timing cover. The dashed line indicates the contact area. Rollings moved the pump ¼-inch forward with an Allstar spacer kit. That required moving the crank and alternator pulleys forward as well. Here's the complete front-drive setup with everything spaced out and moved forward. Rollings says the belt and pulley alignment is better than it was with Price's original configuration.
The Results
Back on the Westech Performance chassis dyno running on 91-octane unleaded gas with 38 degrees total advance, The Carb Shop's metering was virtually spot-on, with only the secondary side requiring slightly leaner jets. Compared to the best baseline run with the known-good shop carb, output improved by more than 133 hp at the wheels-up from the original baseline's 260 whp at 4,910 rpm to 393.6 whp at 6,019 rpm (a 51-percent improvement). The 12.1–lb-ft torque gain was more modest, with the engine now developing 368.6 lb-ft at 4,929 rpm, up from 356.5 lb-ft at 2,742 rpm. A normally aspirated motor's torque potential is basically established by its displacement; big cams and heads tend to just raise the rpm at which the peak occurs.
Never in a million years did I expect such an improvement!” - Sean Price
Also par for the course with larger heads and a bigger cam, there were slight losses below 3,000 rpm-about 10 hp and
20 lb-ft-but that's no big deal on the 1965 Nova with its Tremec five-speed manual trans and 3.73:1-geared 8.8-inch Ford rearend. Driving the car, Price couldn't believe the change, remarking, “I couldn't be
happier.”
The before/after power curve is almost like you're looking at two different motors. Would you believe a whopping 51-percent horsepower gain at the rear wheels-from 260 to 393 whp!
At 180–185 psi, the post-rescue cranking compression was now about 15-psi lower than the car's as-received condition, despite the improvement in static compression ratio from 8.9:1 to 9.5:1, due the Brodix heads' smaller chambers and a thinner GM head gasket. Cylinder pressures are now right on the sweet spot for aluminum-headed, small-block-Chevy, pump-gas engines.
Lessons Learned
It's not rocket science: Stick with known, coordinated parts combos from reputable aftermarket manufacturers. While we all like to save bucks, sometimes trying to save bucks initially ends up costing more in the long run. Expect fit and chassis integration issues with any major upgrade. That's just hot roddin'!
With more than 393 hp at the wheels, it's like Price has a whole new car. He's now planning a chassis rework to manage all those wild horses.
Car owner Sean Price (left) and his pops, Tom, were blown away by the Nova's performance gains. “Thanks, HOT ROD and Rollings!” Previously, we dealt with the 1965 Nova's cam, cylinder head, and valvetrain woes. Now we'll fix the carb, ignition, and fitment issues. The Rollings rescue crew (clockwise from lower left): Norm Rollings, Trevor Reichel, Phillip Soden, Mark Rollings, and Clarence Range. Drilling small throttle-plate holes (A) was an old-school trick to get a motor to idle with huge racing cams and may cause a lean idle mixture on street cars. The Carb Shop installed new blades without holes. Bretzing says, “Today, we calibrate the idle circuit using replaceable air bleeds.” Baseplate-to-metering block interference can sometimes occur at locations B. Price's Street HP main body (on stand) lacks a vacuum transfer slot found on other universal Holley bodies (A). It was incompatible with Price's installed primary metering block that has a transfer hole for a ported vacuum tube (B)-resulting in an “always-dead” port. Bretzing installed the proper block with no transfer slot hole (C). Ported vacuum is still available at D. Usually used only on the secondary side of some larger double-pumpers with 50cc pumps, the brown cam's profile is much more aggressive than the common pink cam usually factory-installed by Holley. Bretzing kept the larger-capacity pump, but stepped its capacity back to the standard 30cc with the pink cam. No. 1 hole position (arrow) offers the greatest shot. The throttle-cable's one-bolt mounting bracket (A) didn't consistently hold adjustment under pedal input; such mounts with no additional locator tab tend to form an axis of rotation. The solution: a rigid two-bolt, billet-aluminum Summit Racing bracket (B) that, as Rollings puts it, “Is steady, adjustable, good-looking, and reasonably priced.” With the thicker throttle bracket, Rollings says, “We didn't want the air cleaner to hit if the throttle wasn't correctly adjusted. We replaced the ¼-inch-rise, air-cleaner base (left) with a ¾-inch-rise base (right).” Also added was a new, flatter lid that proved 10hp better on the dyno. He retained the original K&N filter element. Moroso shims then moved the crank pulley forward, but ARP's balancer bolt was now too short. In the lathe, Rollings enlarged the pulley's center hole so the bolt and washer bore against the harmonic balancer alone. He enlarged the pulley bolt holes from ⅜ to ½ inch, then recentered the pulley on the balancer by sleeving ARP's ⅜-inch pulley bolts with bushing stock. The alternator pulley moves forward with a ¼-inch spacer (arrow) placed on the shaft behind the drive pulley. To regain sufficient thread engagement for the nut's pulley, the pulley's front recess depth was increased by ¼ inch. PCV valve and oil breather/filler provisions were added by machining grommet holes in the bare, tall Brodix valve covers. The sanitary PCV connector consisting of a plastic tube with rubber hose ends is a Dorman OE replacement part used on many GM trucks and vans circa 1985–1995. Price's old PCV valve was reused. From sheep to wolf: Complete and ready to rumble, the Brodix-equipped 350 fits the Nova engine compartment like a glove.
NEED JUNK FIXED?If your car has a gremlin that just won't quit, you could be chosen for Hot Rod to the Rescue. Email us at pitstop@HotRod.com and put “Rescue” in the subject line. Include a description of your problem, your location, a photo of the car, and a daytime phone number.
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