Pontiac 400 Engine Build - Rehabilitating A Wounded Warrior
Rebuilding A '67 400 That Was Wounded From The Factory But Now Generates Nearly 400 HP
From the November, 2010 issue of High Performance Pontiac
By Rocky Rotella
Photography by Rocky Rotella
Chuck Willard, owner of Willard...
Chuck Willard, owner of Willard Auto Machine (WAM) checks the timing on the '67 400 prior to a dyno pull.
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.
The original 335hp YS-code...
The original 335hp YS-code 400 in Alan Fanning's '67 GTO had been rebuilt in the past, but its poor performance indicated something was amiss internally. WAM in Omaha, Nebraska, was enlisted to perform another rebuild. The already-0.030-inch block was bored an additional 0.010 using a torque plate to a total of 4.16 inches. It was then decked and align-honed by WAM machinist Beau Sheffield.
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.
While preparing to undersize...
While preparing to undersize the main and rod journals by 0.010-inch, Willard detected a significant variance in rod-journal phase. Nos. 2, 3, and 4 were at least 15 degrees retarded when compared to No. 1. Since cam timing and spark advance is generally set according to No. 1, three-quarters of this engine's cylinders were operating severely retarded. The factory error was certainly the cause for the 400's chronic operating issues.
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.
Excessive machining was likely...
Excessive machining was likely required to correct the original crankshaft's phasing issue, so another nodular-iron 400 unit was sourced. Its rod-journal phase measured within one degree from front to rear, which Willard says is much more common with original Pontiac cranks. The replacement crank's journals were undersized 0.010 inch, and the unit was fully balanced.
Most Pontiac blocks can accept...
Most Pontiac blocks can accept a 0.060-inch overbore. This particular 400 had already been bored 0.030-inch, but didn't need to go to 0.060 to restore the cylinder-wall surface. Sealed Power offers a number of high-quality forged-aluminum pistons for various Pontiac V-8 engines. It's one of the few companies producing 400 pistons for a 0.040-inch overbore (PN L2262F040). Based on Pontiac's original design, the high-quality durable units were ideal for our application.
Pontiac's cast-iron connecting...
Pontiac's cast-iron connecting rod was used in all production engines from '67 forward, except for the '73-'74 SD-455.
When building high-horsepower...
When building high-horsepower engines (approximately 500 hp and above), 4340-steel forgings are popular, but KRE's forged 5140-steel Pro-Warrior rods (right) are an excellent alternative to reusing stock rods when building a strong performing street engine. Featuring ARP bolts and retailing for around $250 per set, these rods are available from most Pontiac engine builders.
Roller camshafts generally...
Roller camshafts generally reduce friction and allow for a more aggressive lobe profile, which can translate into a slight power increase. While converting an existing engine from a flat-tappet camshaft to a roller can be relatively costly, the cost difference is much more manageable if a new cam is required during an engine rebuild. KRE supplied us with this custom-spec Comp Cams hydraulic-roller, featuring 218/224 degrees of 0.050-inch duration and 0.500-inch valve lift on a 112 LSA. The lifters are Pro-Warrior units.
After installing the oil galley...
After installing the oil galley and coolant plugs, the cam bearings were fitted, the Best Gasket "GraphTite" rope rear main seal was installed, the top half of the main bearings were set into the main saddles, and the crankshaft was dropped into place. The main caps were installed and the bolts of the first four caps were torqued to the factory settings and the endplay was checked.
With the rings in place, the...
With the rings in place, the piston and connecting rod assemblies were inserted into the cylinders, and the rod caps were installed and torqued to the recommended setting. A 60-psi Sealed Power oil pump, the original windage tray, and a stock-replacement Canton oil pan round out the bottom end.
The hydraulic-roller camshaft...
The hydraulic-roller camshaft was installed and degreed to ensure maximum performance. Supplied specifications state the camshaft was ground with its intake centerline (ICL) at 108 degrees, and WAM verified that it was installed as suggested. The numbers were exactly as stated by Comp Cams.
The original No. 670 cylinder...
The original No. 670 cylinder heads were rebuilt during the last engine rebuild and needed only minor repairs this go-around. Their compact 153cc intake ports promote crisp throttle response and excellent low-speed street manners. On our Superflow 110 flowbench, peak intake and exhaust airflow capacity measured 212 and 168 cfm at 28 inches respectively, which is more than sufficient for this particular 400. The existing aftermarket 2.11/1.77-inch stainless steel valves were reused, but new Comp Cams valvesprings were installed.
The No. 670 heads were originally...
The No. 670 heads were originally a closed-chamber casting with a volume that measures roughly 72cc in stock form. These chambers were relieved by KRE during the rebuild and now displace 75 cc's, which produces a pump-gas-friendly compression ratio of 10:1 on the 408. While flowbench testing shows the modification had no effect on airflow numbers, Jeff Kauffman says it's intended to improve overall chamber efficiency, which can be detected on the dyno. The closed-chamber castings generally run best with 36-38 degrees of total spark lead, but the particular 400 produced peak power with just 32 degrees.
The modified No. 670 heads...
The modified No. 670 heads were installed and secured to the block using the original head bolts.
Two hydraulic-roller lifters...
Two hydraulic-roller lifters and two roller rockers were then installed, and an adjustable pushrod was used to check valvetrain geometry to determine required length. While waiting for the custom-length 8.55-inch pushrods to arrive, the engine was masked off and painted in the correct shade of Pontiac silver-blue metallic.
Once the pushrods arrived,...
Once the pushrods arrived, they were installed, along with the Pro-Warrior hydraulic roller lifters, 7/16-inch ARP rocker studs, new Comp Cams guide plates, and 1.5:1 Harland-Sharp roller rockers.
The valves were then adjusted...
The valves were then adjusted to a quarter-turn past zero lash.
Roller camshafts are typically...
Roller camshafts are typically produced from billet steel, and the material doesn't mix well with a traditional cast-iron distributor gear. A bronze or composite distributor gear is required, and the composite offering from BOP Engineering in Jefferson, Wisconsin, is quite popular with Pontiac owners. Retailing for $125, it's more costly than bronze, but its service life is longer.
A 0.030-inch hole was drilled...
A 0.030-inch hole was drilled into the block's rear oil plug to provide a jet of constant lubrication to maximize longevity.
A new Pertronix HEI (PN D1200)...
A new Pertronix HEI (PN D1200) was installed after replacing the supplied gear with the BOP composite unit. On our distributor tester, the HEI provides 22 degrees of centrifugal advance by 3,000 rpm. The high-quality unit is brand-new and includes an adjustable vacuum-advance unit. It retails for $230.
The reproduction Ram Air-style...
The reproduction Ram Air-style manifolds from Ram Air Restorations Enterprises (R.A.R.E.) were purchased and installed on the 400 several years ago. Available with an as-cast outlet diameter of roughly 2.25 inches or bored out to nearly 2.5 inches for improved performance, these 2.5-inch units were ceramic-coated during the rebuild. A pair of 2.5-inch, mandrel-bent downpipes (PN DGA20S) in 409 stainless steel from Pypes maximizes performance on the dyno and in the vehicle.
The 408 was installed onto...
The 408 was installed onto WAM's Land & Sea DYNOmite engine dyno and run in before any pulls were made. Since the engine uses a hydraulic-roller cam, an extended camshaft break-in procedure wasn't required. Instead it was brought up to normal operating temperature, and load and rpm were varied to seat the rings.
Rebuilt using most of its...
Rebuilt using most of its original pieces, a mild hydraulic-roller camshaft, and a free-flow exhaust system, the stock-looking 408 generated 396 hp at 5,300 rpm and 444 lb-ft at 4,200 rpm. The A/F ratio was 12.7:1 to 13.0:1 without the air cleaner, indicating that jetting is good. Average horsepower and torque between 3,000 and 5,400 was 337 and 423, respectively. That's quite impressive considering the conservative approach taken to accommodate the power accessories.
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.
High Performance Pontiac
Engine Buildup Worksheet 1967 400
Engine Displacement: 407.8 ci
Horsepower: 396 at 5,300 rpm
Torque: 444 at 4,200 rpm
Bore/Stroke Ratio: 1.11:1
Rod/Stroke Ratio: 1.77:1
Block Description: YS-code #9786133 400
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
Windage Tray: Factory
Oil Pan: Canton stock-replacement
Oil Pump: Sealed Power PN 224-43364S, 60-psi
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
Valve Seals: Positive
Rocker Studs: ARP 7/16-in
Rocker Arms: Harland-Sharp roller 1.5:1 ratio
Pushrods: Custom length, 8.55-in
Brand: Comp Cams hydraulic-roller
Duration at 0.050: 218/224-deg
Lift: 0.495/0.502-in with 1.5:1 rockers
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
Carb: Rochester Quadrajet 7027263
Size: 750 cfm
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
Distributor: Pertronix HEI D1200
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
Manifolds: Reproduction Ram Air from R.A.R.E.
Primary Diameter: 1.625-in
Downpipes: Pypes stainless-steel, 2.5-in, mandrel-bent (PN DGA20S)
Air Temp: 83-degrees
Barometric Pressure: 28.77 hg
Humidity: 60 percent
Correction Factor: 1.089