Overview of the Pontiac 400 Engine

The Pontiac 400 V8 debuted in 1967 as a replacement for the 389. It displaces exactly 400 cubic inches (6.6 liters) thanks to a 4.12-inch bore and a 3.75-inch stroke. This engine block is a staple of Pontiac’s muscle car era, found in the GTO, Firebird, Grand Prix, and full-size models. What makes the 400 special is its deep-skirt block construction, large main bearings, and excellent oiling system—all attributes that allow it to handle serious power. With the right rotating assembly and cylinder heads, the 400 can easily surpass 500 hp while retaining street manners. The following cost breakdown uses Edelbrock Performer components because they offer a reliable, bolt-on path to that horsepower without requiring custom fabrication or exotic machine work.

Parts List and Expanded Costs

Every build starts with a core short block. We assume you are starting with a rebuildable Pontiac 400 core (prices vary, but a good block can be found for $300–$500). The parts below are selected from Edelbrock’s Performer line where available, complemented by high-quality aftermarket pieces necessary to reach 500 hp. Estimated prices are based on current market averages from major retailers such as Summit Racing and Jegs.

Short Block Components

  • Forged Steel Crankshaft: A stock cast crank can handle about 450 hp, but for reliability at 500 hp you need a forged unit. Eagle and Scat offer 4340 steel cranks for the Pontiac 400 at around $850. (We budget $800–$900.)
  • Forged Connecting Rods: The stock rods are the weak link. Upgrade to a set of 4340 forged I-beam rods, such as those from Scat or Eagle, which run about $500.
  • Forged Pistons: For a 10.0:1 to 10.5:1 compression ratio (ideal with aluminum heads and a moderate cam), a set of forged alloy pistons from Speed-Pro or JE is necessary. Expect to pay around $600 for a set with rings and pins.
  • High‑Performance Timing Set: A billet steel double-roller timing chain set (e.g., Cloyes) costs about $100. It ensures accurate cam timing and reduces stretch under load.

Cylinder Heads and Valvetrain

  • Edelbrock Performer Aluminum Cylinder Heads (PN 60599): These heads flow 270+ cfm out of the box, feature 87cc combustion chambers, and accept standard Pontiac rocker arms. At roughly $1,200 for a pair, they are the single biggest horsepower gain. Their weight reduction also helps front-end handling.
  • Valve Springs and Retainers: Use the spring kit recommended by Edelbrock for the Performer cam (PN 5612) – about $75.
  • Rocker Arms: Stock 1.5:1 rockers work, but upgraded 1.65:1 roller rockers (e.g., Harland Sharp, $250) can add another 10–15 hp. We’ll include $250 in the budget.
  • Pushrods: High‑quality 5/16” or 3/8” hardened pushrods are needed for the longer valve stems; budget $80.

Induction System

  • Edelbrock Performer Intake Manifold (PN 7156): A dual-plane design optimized for the 400’s displacement, it provides strong low- and mid-range torque. Price: $300.
  • Edelbrock Performer 750 CFM Carburetor (PN 1407): The 750 is the sweet spot for a 400 at 500 hp. Electric choke and vacuum secondaries make it street-friendly. Cost: $400.
  • Fuel System Upgrades: A mechanical pump with an adjustable regulator is adequate; budget $100 for pump and filter.

Exhaust and Ignition

  • Headers: Full-length 1¾” primary tube headers from Hooker or Hedman fit most chassis. Ceramic coating helps reduce underhood heat. Cost: $400.
  • Exhaust System: A 3-inch mandrel-bent dual exhaust with X‑pipe and performance mufflers (Flowmaster or Magnaflow) runs about $600 installed (DIY saves $200+).
  • Ignition System: A high-output HEI distributor (MSD or Pertronix) with a rev limiter ensures strong spark. Budget $200.

Miscellaneous and Gaskets

  • Gaskets and Seals: A full Fel-Pro performance gasket set is $80. Add sealants, thread lock, and assembly lube: $50.
  • Oil Pump and Pickup: A Melling high‑volume oil pump (about $60) and matching pickup ($20) are mandatory for longevity.
  • Camshaft and Lifters: Edelbrock Performer Camshaft (PN 7156) – this hydraulic flat-tappet cam offers 214/224 degrees duration at .050”, .443”/.465” lift with 1.5 rockers. It’s designed to match the Performer intake and heads. Cost: $200. You’ll also need new lifters (about $50) and a distributor gear.
  • Contingency Fund: Machine shop work (boring, honing, line boring, decking) can add $500–$800. We include $700 in estimates.

Total Cost Estimate

CategoryEstimated Cost
Short block (crank, rods, pistons, timing set)$2,000
Cylinder heads & valvetrain$1,600
Induction (intake, carb, fuel)$800
Exhaust (headers, system)$1,000
Ignition$200
Camshaft, lifters, gaskets, oil pump$450
Machine work & contingency$700
Parts subtotal$6,750
Labor (if not self-performed)$1,500–$2,500
Total (DIY)$6,750
Total (shopped out)$8,250–$9,250

These figures are in line with the original estimate but adjusted for current market conditions and including critical items like machine work. The DIY total is about $6,750, while a turnkey build including professional assembly and dyno tuning runs $8,000–$9,500. Prices fluctuate, so always check with Summit Racing or Jegs for current deals.

Building Process Overview

Achieving 500 hp requires careful assembly and machining. Here is the recommended sequence.

Machining the Short Block

  • Inspect the block for cracks and measure bores. If taper exceeds 0.002”, bore and hone to the next oversize using a torque plate (adds $200–$300).
  • Align-hone main bearing bores if the crank does not spin freely in the block with new bearings. Typical cost: $150.
  • Deck the block to ensure flatness and achieve a zero-deck height for proper quench. Expect $100–$200.
  • Resize the connecting rods and install new ARP bolts. Many machine shops offer this as part of a rod package.

Assembly Steps

  • Install the camshaft and bearings, verifying cam end-play (0.004”–0.008”).
  • Degree the cam to ensure intake centerline matches Edelbrock’s recommendation (108°). This step is critical for power.
  • Install the crank, rods, and pistons with proper ring gaps (for street use, top gap 0.020”–0.024”). Use assembly lube on all bearing surfaces.
  • Install the timing set with marks aligned; then install the oil pump and pan.
  • Fit the cylinder heads with new gaskets and torque bolts to spec (typically 95–105 ft-lbs in three stages).
  • Install the rocker arms and set valve lash (hydraulic lifters: preload 1/2 turn past zero lash).

Induction, Exhaust, and Ignition

  • Mount the Edelbrock Performer intake with a gasket and torque the bolts to 30–35 ft-lbs in the sequence specified.
  • Adjust the carburetor float level and set idle mixture screws to baseline. Wire the distributor and set initial timing to 12° BTDC with vacuum advance disconnected.
  • Install headers and exhaust system, using quality gaskets and Stage 8 locking fasteners to prevent loose bolts.

Tuning for 500 HP

After break-in (20 minutes at 2,000–2,500 rpm with varying load), tune the carburetor and timing on a dyno. Expect to need jet changes (often one or two sizes richer) and timing adjustments. A professional dyno session (about $500) is recommended to verify horsepower and air-fuel ratios. Many self-tuners can get close with a wideband O2 sensor and careful test drives.

Performance Expectations

With the Edelbrock Performer package and supporting parts, the Pontiac 400 delivers the following on a chassis dyno (corrected to flywheel):

  • Peak Horsepower: 500–520 hp at 5,500–5,800 rpm
  • Peak Torque: 510–530 lb-ft at 4,000–4,200 rpm
  • Redline: 6,000 rpm (safe with forged internals)
  • Street Manners: Idles at 750 rpm with slight lope, excellent vacuum (14–16 inHg) for power brakes.

This combination works well with a wide-ratio 4‑speed or an automatic (TH400/200‑4R) with 3.55–3.73 gears. Quarter-mile times in a 3,600‑lb car should be in the low-12-second range with good traction.

Conclusion

Building a 500-horsepower Pontiac 400 with Edelbrock Performer parts is a straightforward project for a well-equipped home mechanic. The total cost of approximately $7,000 (DIY) to $9,000 (shop built) is competitive for the power level, especially given the reliability and parts availability of the Edelbrock system. By following the machining and assembly steps outlined here, you can create a powerful, durable street engine that honors the Pontiac legacy. For additional technical resources, consult the Edelbrock Tech Support page or the Performance Years Pontiac forums for community‑tested tuning tips. With careful planning, that 500 hp goal is within reach.