Have you ever had an engine that just didn't seem to run right? You know the kind-one assembled using a proven combination of complementing components that should run and drive much better than it actually does. There's almost always a root cause: It can stem from improper machining, poor assembly, an unmatched combination, or even unrealistic expectations.

Alan Fanning of Fremont, Nebraska, was one such owner who was disappointed in his Pontiac's performance. A previous owner had rebuilt his '67 GTO's original 335hp 400 four-barrel, but it wasn't operating to Alan's expectations. He rebuilt it again in the late '90s, reusing the stock components, but adding reproduction '67 400 H.O. exhaust manifolds, a then-popular hydraulic flat-tappet camshaft, and a set of dished pistons to provide a pump-gas-friendly compression ratio of 8.25:1. He wasn't totally happy with his new engine's performance, either, and spent the next decade searching for the cause.

Fanning enlisted our assistance a couple of years ago. The major issues we found included chronic detonation, occasional overheating, and continuous run-on. Even though the 400 hadn't been driven that many miles since its last rebuild, it was apparent that something was amiss internally, requiring yet another rebuild to correct the issues. This time, however, careful attention would be given to every tolerance. We reasoned we could also modernize the 400 with roller technology.

Follow along as we rebuild and dyno test an otherwise-stock '67 400. We'll cover the highlights of the build in this story. Complete assembly procedures, torque specs, and clearances can be found in the '67 Pontiac service manual.

Plan Of Action
Establishing a sound plan of action should be the first step of any rebuild, and it was extremely important in Fanning's instance. Not only had prior rebuilds produced less-than-desirable results, but Fanning's particular GTO was originally equipped with myriad convenience options, and retains its Turbo 400 backed by a stock-stall torque converter, 2.93 rear gearing, and functional A/C. This means the 400 spends most of its time operating at lower rpm, and has additional load placed on it at idle when the A/C is on.

Focusing on maintaining stock appearance and producing as much low-speed power as possible, we worked with Jeff Kauffman of Kauffman Racing Equipment (KRE) in Glenmont, Ohio, to obtain a mild hydraulic-roller camshaft, which would eliminate any chance of flat-tappet failure related to modern oil quality. We needed to maintain good idle quality and low-speed street manners, while producing strong horsepower numbers. We were less concerned with peak horsepower, but wanted to maximize average power from idle to approximately 5,200 rpm and have a wider lobe-separation angle to improve idle quality. A custom-spec Comp Cams grind was on our doorstep within days.

The Rehabilitation
During teardown we found many irregularities within the 400, but nothing that conclusively pointed toward the cause for its poor performance. We enlisted Chuck Willard of Willard Auto Machine (WAM) in Omaha, Nebraska, to perform all the necessary machining, careful assembly of the components, and to measure the engine's output on his Land & Sea DYNOmite engine dyno.

Willard planned to machine the block and crankshaft as if it was any other rebuild. The YS-code block checked out perfectly after being bored to a total of 0.040 over. The crankshaft required some additional attention, however. Its main and rod journals were at standard dimensions, which meant that machining wasn't necessary during previous rebuilds. While it's possible the journals could've been polished, Willard planned to undersize them by 0.010-inch, given the engine's history.

After installing the crankshaft in his grinder, Willard checked the rod-journal tolerances using a dial indicator and noticed a significant variance. The Nos. 2, 3, and 4 rod journals were out of phase when compared to No. 1. After equating, he estimates the last three journals were approximately 15 degrees retarded when compared to the first. Since no prior machining had ever been performed on the crankshaft, it seems to be an error that occurred at Pontiac-the 400 hadn't operated correctly since the day it was assembled in 1967.

With this severe degree of phase variance among the rod journals, there was concern as to whether enough material would remain after machining to use common undersized Pontiac rod bearings. A suitable replacement crank was located instead, and the build progressed with a sense of relief from Fanning, who was elated at the "smoking-gun" find. The rest of the rebuild went without incident, and once on the dyno, the stock-appearing '67 400 churned out 396 hp at 5,300 rpm and 444 lb-ft of torque at 4,200 rpm-outstanding results from a relatively mild combination.

Conclusion
The GTO's YS-code 400 was factory rated at 335 hp, but after finding significant issues with the original crankshaft, it's quite obvious this Pontiac never performed up to its potential-even when new. With the addition of 400 H.O. exhaust manifolds and a mild hydraulic-roller camshaft, the otherwise numbers-matching '67 400 surpassed the H.O.'s original 360hp rating by nearly 40 hp, while maintaining 445 lb-ft of peak torque. That's sure to give this GTO's owner a newfound sense of Pontiac power at all engine speeds.

RPM HP TQ
3,000 240 421
3,100 255 430
3,200 262 430
3,300 271 430
3,400 279 431
3,500 288 434
3,600 301 436
3,700 310 438
3,800 318 438
3,900 323 435
4,000 336 437
4,100 347 442
4,200 355 444
4,300 358 437
4,400 364 434
4,500 368 431
4,600 370 422
4,700 375 418
4,800 380 416
4,900 382 409
5,000 383 402
5,100 384 395
5,200 389 392
5,300 396 392
5,400 384 376
AVG 337 423

High Performance Pontiac
Engine Buildup Worksheet 1967 400

Engine
Engine Displacement: 407.8 ci
Horsepower: 396 at 5,300 rpm
Torque: 444 at 4,200 rpm
Bore/Stroke: 4.16x3.75
Bore/Stroke Ratio: 1.11:1
Rod/Stroke Ratio: 1.77:1

Bottom End
Block Description: YS-code #9786133 400
Year: 1967
Preparation: Bored 0.040-in
Deck Height: Zero
Crankshaft: Nodular-iron 3.75-in stroke
Preparation: Main and rod journals undersized, 0.010-in, fully polished
Balancer: Stock Pontiac
Rods: KRE Pro-Warrior, forged 5140-steel , 6.625-in length
Preparation: Fit pistons pins
Bearings: Federal Mogul, PN 8-7050CH-10 (rods) and PN 113M-10 (mains)
Pistons: Sealed Power forged-aluminum , PN L2262F-040
Piston Pins: Sealed Power pressed
Piston Rings: Sealed Power, PN E299K-040
Fasteners: Original Pontiac
Balanced: Yes

Oiling System
Windage Tray: Factory
Oil Pan: Canton stock-replacement
Oil Pump: Sealed Power PN 224-43364S, 60-psi

Heads
Casting Number: 670
Chamber: Originally closed
Head Mods: Chambers relieved
Combustion Chamber Volume: 75cc (after modifications)
Flow at 28 inches: 212/168 at 0.525-in
Compression Ratio: 10.1:1
Valves: Ferrea stainless-steel 2.11/1.77-in
Angles: Multiple-angle seats with 30-deg intake, 45-deg exhaust
Retainers and Keepers: Comp Cams
Valveguides: Bronze
Valve Seals: Positive
Rocker Studs: ARP 7/16-in
Rocker Arms: Harland-Sharp roller 1.5:1 ratio
Pushrods: Custom length, 8.55-in

Cam
Brand: Comp Cams hydraulic-roller
Duration at 0.050: 218/224-deg
Lift: 0.495/0.502-in with 1.5:1 rockers
Centerline: 108-deg
Lobe Separation Angle: 112-deg
Lifters: KRE Pro-Warrior hydraulic-roller
Valvesprings: Comp Cams PN 995-16
Install Height: 1.75-in
Seat Pressure: 135-lb/in intake, 125-lb/in exhaust
Open Pressure 350-lb/in intake, 350-lb/in exhaust
Timing Chain: Sealed Power PN 220-3112 roller

Induction
Carb: Rochester Quadrajet 7027263
Size: 750 cfm
Mods: None
Primary Jets: 0.073-in
Primary Metering Rods: 0.041-in
Secondary Metering Rods: BF 0.0397-in
Fuel Pump: Carter stock-replacement
Fuel Line: Original
Intake Manifold: PN 9786286, 67 cast-iron dual-plane

Ignition
Distributor: Pertronix HEI D1200
Coil: Pertronix
Module: Pertronix
Wires: AC Delco 8mm
Total Timing: 32-deg
Initial Advance: 10-deg
Mechanical Advance: 22-deg by 3,000 rpm
Vacuum Advance: Adjustable
Spark Plugs: AC Delco R45

Exhaust
Manifolds: Reproduction Ram Air from R.A.R.E.
Primary Diameter: 1.625-in
Collector: 2.5-in
Downpipes: Pypes stainless-steel, 2.5-in, mandrel-bent (PN DGA20S)

Gaskets
Brand: Fel-Pro

Weather
Air Temp: 83-degrees
Barometric Pressure: 28.77 hg
Humidity: 60 percent
Correction Factor: 1.089

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