Some hobbyists have no qualms pushing the envelope when attempting to maximize the performance of a combination, and that can include any component of the drivetrain. Without careful attention to detail, however, one can create a temperamental vehicle that's unhappy cruising at any speed and/or an engine unwilling to run on pump gas. Few can then blame such owners who are reluctant to venture far from home, fearing major malfunction or the inability to find quality fuel on the open road.
There are others, however, who wish to combine strong performance and a low-maintenance design. Though it may ultimately cost a few horsepower, the result is usually an engine that can be driven any distance or speed while happily operating on marginal-quality fuel. If this sounds desirable, then a powerplant like that featured here is for you. Follow along as we document the assembly of a 474ci engine that produces high horsepower on ordinary pump gas.
Dave Hall of Restore A Musclecar in Lincoln, Nebraska, explains to HPP his desire to boost the performance of his company's flagship show car. "Our '77 Trans Am gets driven long distances on events like the Bandit Run, and our technician, Gary Otto, rebuilt its T/A 6.6 engine during the total restoration a few years back. He mildly ported the original 6X-4 cylinder heads and added a Performer RPM intake manifold and Demon carburetor. The roller camshaft and rocker arms came from Butler Performance."
Of the combination, Dave states, "It runs pretty well, especially with headers, a five-speed manual transmission, and deep rear gears, but we kept the engine build somewhat mild because of its intended usage." The company went all out with the suspension and brakes, and the T/A's looks and sound seemed to draw attention, but it became quickly evident that its straight line performance prowess didn't match its heavily modified, corner-carving image.
Hall sought the expertise of Butler Performance in Leoma, Tennessee, and explained his goals to David Butler. "I wanted something that produced around 550-600 hp using a stock Pontiac block," he says. "I also told him that the combination needed to be suitable for in-town cruising or cross-country trips, and that meant that power brakes and air conditioning were a must.
"He laid out a 474ci combination that would suit our needs using a spare 455 block I had. He then provided us with virtually everything necessary to assemble the long-block, including a complete rotating assembly with forged components."
Starting with a two-bolt '71 455ci block and working with the measurements that Butler supplied, Hall had machinist Jon Wischmann prepare the block to accommodate the waiting internals. After complete machining, technician Gary Otto assembled the short-block with relative ease. "We checked all the clearances along the way, and everything was within the stated specifications," he adds. Once the 474ci was fully assembled, Hall and his crew gathered at Spanel Engines in Lincoln for dyno tuning.
A series of eight pulls were made on the Superflow SF-901 dyno, and most consisted of unique timing and/or carburetor settings. All numbers were corrected to standard conditions, and at the end of the session, the mill had peaked at an astounding 578 hp and 588 lb-ft of torque using 92-octane fuel-well within Hall's request of Butler.
Analyzing The Results
After digesting the results, David Butler comments, "The numbers look very good. We've seen 600 hp and 600 lb-ft of torque, sometimes slightly more from this combination with compression toward 11.5:1, which should operate suitably on 92- to 93-octane fuel with the aluminum heads. This wasn't a 'dyno' combo, however, which might typically include borderline compression, a huge camshaft, and a large carburetor. Instead, we took a conservative approach based on the vehicle's intended use."
Dave Hall of Restore A Muscle Car in Lincoln, Nebraska, was seeking to significantly impro
Machinist Jon Wischmann prepares Hall's two-bolt '71 No. 485428 455ci block for the rotati
With machine work complete, technician Gary Otto thoroughly washes the block with soap and
...and threads a tap into each bolt hole to remove the debris that's accumulated over the
Working within Hall's parameters, Butler Performance sent a custom-ground hydraulic-roller
With the block back from paint, Otto installs the camshaft first. He feels this method giv
The rotating assembly kit that Butler Performance recommended for the build includes this
Also included in the rotating assembly kit from Butler Performance are forged-steel Eagle
The piston rings are file fit to a gap of 0.018 inch. Otto then installs the rings and ful
He continues, "We knew the engine would operate on 89-octane at times, so we limited its compression ratio to just under 10:1. Wisely, 92-octane was used during the dyno session, and this is likely why it peaked with 42 degrees of total timing instead of the normal 36-38 we see when combining Edelbrock heads with 92-octane fuel. I'm confident it will produce similar peak power numbers with less timing when running on 89-octane; I suggest that timing be set to 38 degrees in those conditions."
Butler says he's pleased to see horsepower peak at 5,500 rpm-a relatively low number for a combination such as this. "It carried over 530 lb-ft of torque for nearly the entire pull, and that should make for a great street engine that can be driven in any situation with little to no maintenance. I think the team at Restore A Muscle Car will be very happy with this combination."
Hall contends, "I really didn't know what to expect going into the dyno session. There are countless factors that can affect the outcome, but we've always had great support from the team at Butler Performance, and David was there to assist every step of the way. I'm very pleased with the results, especially knowing that I can pull into any gas station, fill the tank with 89-octane fuel, and still produce that much horsepower. It's certainly a combination we'll offer to our customers."
While additional compression and extended camshaft duration and valve lift might yield greater output from the 474ci, few will argue that 578 hp and 588 lb-ft of torque aren't impressive, particularly when considering the parameters set forth. Once installed, it should perform admirably in virtually any condition while maintaining excellent drivability at all speeds, and that's exactly what this customer ordered.
A point to keep in mind about our feature build is that not only does it highlight the power a moderately built Pontiac produces, it also proves that hobbyists needn't be professional engine builders to achieve such results. With precise block machining, any technician or competent hobbyist can assemble a large-cube mill like this with minimal effort-and seeing it generate 578 hp makes that effort worthwhile.
Wth the rod bearings and caps now installed, and having already checked rod-bearing cleara
Here is the bottom end awaiting the oil pump, pickup, and pan installation.
From the topside, the flat-top pistons with valve reliefs are revealed.
Otto installed the adjustable timing set from Butler Performance and employs a Comp Cams c
Butler Performance prepared a pair of 87cc Edelbrock aluminum cylinder heads specifically
...and the supplied specification sheet reveals that airflow at 0.700 inch is 316 and 236
Normally milled to minimize volume after polishing, the combustion chambers of this pair m
The Victor intake manifold's large plenum and smoothly contoured runners provide good flow
While the 2.11-inch intake valve is retained on the E-heads, the exhaust valve diameter is
After Otto installs the cylinder heads onto the short-block and torques the ARP head bolts
After installing a host of ancillary components, including an aluminum valley pan, a Canto
Timing was adjusted a few times during the session. Note that we utilize a previously used
At the console of the Superflow SF-901 engine dynamometer sits Chuck Spanel. After proper
|Engine Buildup Worksheet|
|Engine Displacement||473.5 ci|
|Peak Horsepower||578 at 5,500 rpm|
|Peak Torque||588 lb-ft at 4,700 rpm|
|Block Description||YC-code No. 485428|
|Block Preparation||Bored 0.060-in|
|Crankshaft||Butler Performance, forged-steel, 4.25-in stroke, 3.25-in main journal, 2.20-in rod journal|
|Crank Preparation||Normal |
|Main Caps||Pro-Gram Engineering, No. PRO-P455F front, No. PRO-P455C center three, No. PRO-P455R rear|
|Main Bearing Clearance||0.003 in|
|Balancer||Performance Street Balancer No. PBO-PB1056ST|
|Rods||Eagle Specialty Products, forged-steel, H-beam, 6.800-in length, 7/16-in ARP bolts|
|Bearings||Federal Mogul No. 151M-STD main journal, Federal Mogul 8-7200CH-STD rod journal|
|Piston||Ross custom, forged-aluminum, 4.211-in diameter, flat-top, 439.5 grams, 8.5cc reliefs|
|Piston to Deck Height||Zero|
|Piston Pins||Ferrea No. P70028-8, forged-alloy, 0.990-in diameter, 138 grams |
|Piston Rings||Total Seal No. CR3455-65, plasma-moly, file-fit, 0.018-in gap|
|Fasteners||ARP 194-5601 four-bolt main-stud kit|
|Oil Pan||Canton No. 15-450, road-race|
|Oil Pump||Melling M54F|
|Oil||Shell Rotella 30W|
|Casting Number||Edelbrock No. 60569-2|
|Combustion Chamber Volume||90 cc’s|
|Head Mods||Fully ported intake and exhaust ports|
|Intake Port Volume||Approx. 220 cc’s|
|Intake/Exhaust Flow Ratio||75 percent |
|Intake/Exhaust Flow at 28-in:|
|0.200 ||140/86 cfm|
|Intake Valve||Ferrea No. 5073, stainless steel, 2.11-in, 5.100-in length|
|Exhaust Valve||Ferrea No. 5144, stainless steel, 1.77-in, 5.100-in length|
|Angles||Multi-angle with 45-deg seats|
|Retainers||Comp Cams No. 740-16, 10 deg|
|Locks||Comp Cams No. 611-16, 10 deg |
|Valvesprings||Lunati No. 73100-16 |
|Install Height||1.79 in|
|Seat Pressure||137 psi|
|Open Pressure||338 psi|
|Valveguides||Bronze, 0.530-in diameter|
|Rocker Studs||ARP No. 100-7101, 7/16-in|
|Rocker Arms||Comp Cams No. 19060, full roller|
|Rocker Ratio||1.5:1 |
|Pushrods||Butler Performance No. SBR-581-R-16, 5/16-in diameter, 8.80-in length, chrome-moly|
|Fasteners||ARP No. 190-3605 head-bolt kit|
|Brand||Comp Cams custom Butler grind|
|Duration at 0.050||242/248-deg|
|Lift||0.540/0.562-in with 1.5:1 rockers |
|Intake Centerline||Installed at 106.5 deg|
|Lobe Separation Angle||110 deg|
|Lifters||Comp Cams No. 857-16|
|Timing Set||Butler Performance No. JPP-5614LB-5, 0.005-in undersized, nine-way adjustable|
|Timing Chain Type||Billet-steel roller |
|Distributor Driven Gear||BOP No. PDG38, polymer, for MSD distributor|
|Carb||Barry Grant Demon|
|Jets Front/Rear||No. 81/89|
|Fuel Pump||RobbMc No. 1006|
|Intake Manifold||Edelbrock Victor No. 2957, modified by Butler Performance|
|Spacer||1-in phenolic, open design|
|Fuel Used for Test||92-octane BP|
|Distributor||MSD Billet HEI|
|Coil||MSD in-cap |
|Total Timing||40 deg|
|Spark Plugs||NGK No. R5671A-7, gapped at 0.050 in|
|Brand||No. SPM-KSX703-74, complete Pontiac overhaul|
|At The Dyno|
|Actual Air temp ||74 deg F; Baro: 28.59-in of Hg; Humidity: 45 percent|
|Corrected To||Air temp: 60 deg F; Baro: 29.92-in of Hg; Humidity: dry|
|Corrected Dyno Results|
Pull LogPull 1: 81/89 jets; 40 deg; 577 hp at 5,400 rpm; 588 lb-ft at 4,800 rpmPull 2: 77/85 jets; 40 deg; 567 hp at 5,400 rpm; 585 lb-ft at 4,600 rpmPull 3: 77/85 jets; 38 deg; 564 hp at 5,300 rpm; 582 lb-ft at 4,700 rpmPull 4: 75/83 jets; 38 deg; 547 hp at 5,500 rpm; 568 lb-ft at 4,800 rpmPull 5: 75/83 jets; 35 deg; 547 hp at 5,300 rpm; 568 lb-ft at 4,600 rpmPull 6: 81/89 jets; 40 deg; 570 hp at 5,500 rpm; 586 lb-ft at 4,600 rpmPull 7: 81/89 jets; 42 deg; 578 hp at 5,500 rpm; 588 lb-ft at 4,700 rpm
Average Horsepower/Torque from 3,200 to 5,600 rpmPull 1: 470/559Pull 2: 463/550Pull 3: 463/550Pull 4: 451/536Pull 5: 452/539Pull 6: 468/558Pull 7: 480/561