Dyno Testing A Home-Built Pontiac Motor - Backyard-Built Bruiser

Cylinder Head Flow In CFM
Lift	Intake	Exhaust
0.100	75.6	62.5
0.200	148.3	118.7
0.300	210.1	174.0
0.400	263.3	213.9
0.500	304.3	234.4
0.600	323.2	243.3
0.700	332.8	246.4

Building A Performance Pontiac Motor Ross Pistons

Speed Pro file to fit 1/16-inch rings and a 3/16 oil ring were used on the Ross pistons. The compression height of the piston is 1.290 inches, thanks to the longer-than-stock 6.800-inch rods (stock is 6.625 inches). Some engine builders like long rods because of increased dwell time at top dead center, less angularity of the rod (which results in less side loading), quicker building cylinder pressure and the piston can be made shorter, therefore lighter. When using the Eagle crank, it also becomes a matter of economics. With only the 2.200-inch rod journal available, the 6.800-inch rod is simply a big block Chevy piece, which is affordable. In order to get a 6.625-inch rod with 2.200 big end, you have to go custom and that gets expensive.

HPP Engine Buildup Worksheet

Engine Displacement: 468
Horsepower: 644
Torque: 622
Bore/Stroke: 4.190/4.250
Block/Crank combo: 400 Pontiac / Eagle Cast
Bore/Stroke ratio: .986:1
Rod/Stroke ratio: 1.6:1

Bottom End

Block description: 400 Pontiac Block #481988
Year: 1975
Preparation: Square decked, bored to 4.190-in, installed 4 Program Engineering 4-bolt main caps, line honed, rotating assembly balanced
Deck Height: 10.215-in
Crank: Eagle cast steel, 4.250-in stroke, 3.00 in mains
Preparation: Balanced, oil holes chamfered
Balancer: Professional Products
Rods: Eagle, H-beam, forged steel
Rod length: 6.800-in
Preparation: Balanced
Bearings: Federal Mogul
Pistons: Ross forged, 23cc dish
Preparation: Smoothed all piston face edges
Piston to deck height: 0.000-in
Piston pins: Ross
Method used to retain piston pins in pistons: Spiral locks
Rings: Speed Pro File to Fit, plasma moly top, cast iron second stainless steel oil ring.
Preparation: File to Fit for end gap
Rod bolts: ARP, 8740
Head studs: ARP
Main studs: ARP

Cam

Brand: Bullet solid roller
Duration at 0.050: 263/271
Lift: 0.700/0.700
Centerline: 108-deg
Lobe separation angle: 108-deg
Installed position: 105.5-deg
Lifters: Crower roller
Valvesprings: Competition Products, Electro-polished
Seat pressure: 220 lbs
Open pressure: 600 lbs
Timing chain: JBP, 9-way roller

Building A Performance Pontiac Motor Camshaft

This Bullet solid roller cam features duration at 0.050 of 263/271-degrees and 0.700/0.700 lift.

Induction

Carb: Holley Dominator 8896
Size cfm: 1,050
Mods: Out of the box, jetted for optimal A/F ratio
Jets
- Primary: #92
- Secondary: #92
Fuel pump: Mallory 250 gph (dyno)
Fuel regulator: Mallory (dyno)
Fuel line size: -8
Intake manifold: Victor, single-plane
Mods: SD ported runners, Cygan finished with additional flange to runner porting and installed Brodix turtle.

Oiling System

Windage: Pontiac full-length
Oil pan: Pontiac
Preparation: Install baffle and trap door in pan
Oil pump: Melling 54D
Preparation: Weld pickup to pump, shim spring to desired oil pressure

Building A Performance Pontiac Motor Machined Motor

For those of you who just have to see clean parts, here is the block freshly machined prior to assembly. The front of the block on the passenger side had to be slightly clearanced for the crank counterweight. (Photo by Gary Cygan Jr.)

Heads

Brand: Edelbrock
Head mods: Race ported and custom chambered by Dave Bisschop at SD Performance
Combustion chamber volume: 64 ccs
Maximum flow at 28 inches of water
Intake: 330 cfm at 0.700-in lift
Exhaust: 246.4 cfm at 0.700-in lift
Compression Ratio: 11.07:1
Valves: Ferrea SS
Intake size: 2.19-in
Exhaust size: 1.77-in
Angles used in valve job: Multiple
Mods: Milled heads to decrease chamber volume, and port matched to intake manifold
Retainers: Titanium 10-deg
Keepers: 10-deg
Valve guides: Bronze
Valve seals: PC
Rocker studs: ARP
Rocker arms: Harland Sharp roller
Rocker arm ratio: 1.65:1
Pushrods: JBP custom
Diameter: 5/16-in
Length: 9.300-in