With all of the aftermarket engine parts that have been released over the past few years, HPP has been flush with announcements, overviews, buildups, and tests featuring many of the these new goodies. But for this excursion into Pontiac power, we are taking a more traditional direction.
Those of you who are familiar with Jim Taylor Engine Service know that Jim enjoys building street and race powerplants that use as much of what the factory gave us as possible, and the choice of components for this race engine reflects that sentiment. Here it's the combination of the parts that are key in both making power and maintaining durability.
To that end, Taylor gathered some special factory pieces like a four-bolt main '70 455 block because "the '70 blocks seem to have less core shift than later blocks," he says. Next up was a 428 nodular-iron crank with its 4.00-inch stroke and a set of rare Ram Air-IV heads.
Why a 428 crank in a 455 block? According to Taylor there are a few reasons. "The rod/stroke ratio is better, but there is more to it than that. The loading is different with the 4.00-inch stroke of the 428 versus the 455's 4.210-inch stroke because of the crank's offset--meaning the connecting rod journal is closer to the centerline of the crank. As a result, the engine revs more quickly, seems to be easier on bearings, and just is more efficient. You do get more torque with the 455, but it's not enough of a difference to offset the 428 crank's advantages, especially in a light drag car."
Another aspect to the combination is a longer-than-stock connecting rod that Jim says simply makes for a more favorable rod-stroke ratio that ultimately results in more power.
The Ram Air-IV heads can be worked to flow 300 cfm, and Jim says that 300-306 cfm is what he considers to be safe. "At this level, the customer won't have to worry about water in the ports or other failures," he said. Taylor also related that at 300 cfm and with 320-fps velocity, 440 engines have the potential to produce up to 720 horses.
For the intake ports, Jim described the porting procedure thusly, "The roof is lifted to straighten the port as much as possible, and the cross-sectional area at the pushrod bulge is unified. The port floor is lifted with epoxy about the same amount as the roof was lifted. In the valve pocket, the bowl area is made as concentric as possible. Then the short-turn radius is widened and contoured with a specific radius."
"On the exhaust side, the short-turn radius is widened, and the bowl under the valve seat is enlarged but not bigger than the valve seat area--and that's about it."
However, Taylor warned that the 300-cfm intake flow must be maintained through the intake tract and equalized. To that end, the Victor Dominator intake received a Dittmer turtle and was welded and then ported. "Any unmodified cast manifold, when attached to the head, will have a different affect on each port it feeds. The objective is to have all of the intake valves see the same volume at the same velocity each time the valve opens. This is known as flow balancing. Flow balance and flow charge are major contributors to high-horsepower-to-cubic-inch ratios," Jim shared.
With the intake manifold on the head, flow is 303 cfm and with a header on the head, exhaust flow is 215 cfm. This results in a 70-percent exhaust-to-intake flow ratio. Though 75 to 80 percent has been accepted as optimum over the years, Taylor has found that his engines can make just as much power at this level.
There are plenty more aspects and parts to discuss, but the rest is best done in the captions. All totaled, this combination is worth 659 horsepower and over 600 lb-ft of torque on the dyno. Since Pontiac blocks have been known to split up the middle over 700 hp, at 659 there is a durability cushion built in, and there are bragging rights for getting there with a factory-issue block/crank/head combo.
Taylor builds this combination for a multitude of racers. Since the first engine that we dyno'd was already close to completion when we first saw it, some of the photos here are from a twin that is currently going together, but the recipe is the same. Obviously, this will not be a nut-and-bolt buildup story, but rather a discussion of the more interesting aspects of the engine with dyno results to back-up Taylor's build philosophy.
THE BEST DYNO PULL
After adjusting jetting and timing and making six pulls through the course of the day, the best pulls was achieved with #96 jets in the Holley and 35-degrees total timing, which is what the engine started with (for example, a pull with 37-degree timing and #94 jets dropped horsepower by 10 because of a lean condition). Notice that the pull began past the torque peak. This is because the dyno brake couldn't hold the engine at a lower rpm.
RPM Horsepower Torque 4,800 554.7 604.6 4,{{{900}}} 559.9 599.8 5,000 568.9 596.8 5,{{{100}}} 576.0 592.8 5,{{{200}}} 584.7 590.1 5,300 593.8 587.2 5,400 602.2 585.5 5,500 610.7 581.7 5,600 617.3 577.9 5,700 624.2 573.7 5,800 629.5 568.0 5,900 634.6 563.9 6,000 639.2 558.6 6,100 645.0 555.4 6,200 650.5 550.3 6,300 654.5 544.4 6,400 657.2 538.6 6,500 659.4 532.5 6,600 658.3 523.4 6,700 657.5 515.4 6,800 655.7 506.0 6,900 653.0 496.8 HIGH PERFORMANCE PONTIAC ENGINE BUILDUP WORKSHEET Engine Displacement: 440 ci Horsepower: 659 Torque: 604 lb-ft Bore/Stroke: 4.188"/4.00" Block/Crank combo: 455/428 Bore/Stroke ratio: 1.047" Rod/Stroke ratio: 1.675" BOTTOM END Block description: 1970 455 {{{XF}}} code Preparation: Degrease, magnaflux, install four Nunzi four-bolt main caps, mill to even the decks, fill with hard block with torque plate, tap lifter feeds for screw-in restrictors, bore and hone with torque plate, tap lifter gallery ends for 3/8" NPT plugs, O-ring deck for copper head gasket Deck Height: 10.200" Crank: 1969 428, nodular iron, standard journals Preparation: Cut mains .010", cut rod journals .050" for Howard's rods 2.200" big end, adjust index (degrees apart of the rod journals), adjust stroke to 4.00" at all journals, radius oil holes, polish Balancer: BHJ, Elastomer, 6.8" diameter, PN PO-IB-7 Rods: Howard's forged steel Rod length: 6.700" Preparation: Install Crower .990 bushings, measure bearing end diameter at torque spec, check all dimensions, wash Bearings: Mains-Federal Mogul 151 M10 HD, rods-Federal Mogul B.B. Chevy HD PN 87200CH STD Preparation: Verify size, check locking tang for fit in rods, wash Pistons: SRP forged, full floating pin, 1/16", 1/16", 3/16" ring grooves Preparation: Measure, check pin fit, measure ring grooves for width and depth Piston to deck height: .008" Piston Pins: SRP floating with spiral locks Rings: C&A ZG with light tension oil ring, Moly top ring, ductile iron zero gap second ring Preparation: Measure width, inspect, file to fit Rod bolts/head studs/main studs: ARP OILING SYSTEM Windage tray brand: Original Pontiac modified Crank scraper: Custom-made at Jim Taylor Engine Service Oil pan: Moroso 8-quart Oil pump: Sealed Power 60lb, Nunzi's pump drive Preparation: Disassemble, inspect, wash HEADS Casting number: 614 Service Replacement R/A-IV Chamber Open/closed: Open Head mods: Porting on intake and exhaust, bronze guides, receiver grooves for O-rings Combustion chamber volume: 66 cc Flow at 28 inches of water: Intake: 300 cfm at .700 lift Exhaust: 205 cfm at .700 lift Compression Ratio: 12:1 Valves: 2.11" Ferrea {{{6000}}} series int./1.77" 6000 series exhaust Retainers: Comp Cams Titanium Keepers: Comp Cams 10° with lash cap Valve guides: Bronze Rocker studs: ARP, Pontiac guide plates, Nunzi's rocker stud girdle Rocker arms: Crower 1.65:1 roller Pushrods: Smith Brothers Diameter: 5/16" Length: 9.150" CAM Brand: Crane 8620 billet solid roller with TFX grind Duration at .050: 272°/278° Lift: .420/.420 lobe, .670/.670 net at the valve Centerline: 110° Lobe Separation angle: 112° Installed position: 110° Lifters: Crower roller Valve springs: Comp Cams #999 triple Seat pressure: 200 lbs Open pressure: 600 lbs Timing chain: Rollmaster double sprocket INDUCTION Carb: Holley HP Size cfm: 1050 Jets Primary: #96 Secondary: #96 Fuel pump: Dyno set up Capacity: 300 gph Fuel line size: Dyno set up 3/8" Intake manifold: Edelbrock Victor Dominator, single-plane Mods: Welded and ported IGNITION Distributor: Factory Pontiac with Bronze gear and MSD Crank Trigger system Amplifier: MSD 7AL