Muscle Mustangs & Fast FordsHow To Engine
Kaase P-51 Heads on a 1,014HP Basic Big-Block
We use Kaase P-51 heads and a 557-inch stroker to make big, reliable street/strip power.
Knowing we had enough head flow to meet our goals, we turned our attention to the camshaft and intake manifold. Crane supplied a dual-pattern, solid-roller profile that offered a 0.746/0.732 lift split, a 272/280 duration split, and 114-degree LSA. Healthy by any standard, the cam was teamed with a set of roller lifters; an adjustable, billet, double-roller timing chain; and hardened pushrod all from Crane Cams. Crane also supplied the necessary 1.73-ratio, aluminum roller rockers and timing button to keep the roller cam properly located. Though available for flat-tappet and hydraulic roller applications, the Kaase heads were equipped with roller springs designed for cams up to 0.800-inch lift. Topping the heads was an Edelbrock Victor 460 intake designed to accept a 4500-series Dominator carburetor.
Feeding air and fuel to the stroker was a Holley 1150 Ultra Dominator. The word trick hardly does justice to these new carburetors from Holley, but know that the thing was nearly spot on right out of the box. We tried changing jets just because we felt guilty about not doing so, but were rewarded with changes of just a couple horsepower.
To illustrate the impressive power offered by the Kaase heads, the 557 stroker was run with an Aeromotive fuel pump, an MSD ignition system and 2.25-inch Hooker headers. Filled first with Lucas break-in oil and a bottle of (high-zinc) break-in additive, the Milodon pan was eventually filled with 5W-30 synthetic for the power runs.
After a pair of break-in cycles and some timing sweeps, the 557 eventually spit out 754 hp at 6,300 rpm and 713 lb-ft of torque at 4,700 rpm. Remember, this was with a static compression ratio below 10.5:1 and a simple oiling system (meaning no windage tray). We noticed the big motor was very sensitive to oil level and having too much oil limited power. In fact, the power climbed each time we drained a quart out until we started to get a drop in oil pressure. What this motor really needed was a windage tray—our fault, not Milodon's, as it only supplied what we asked for.
Satisfied with our normally aspirated power, we added a small shot of nitrous. NOS supplied an adjustable Cheater (plate) system designed for our 4500-series Holley Dominator. Adjustable from 150hp to 250hp, the system was perfectly suited for our street-strip application.
Math told us the 750hp 557 stroker would require the full 250hp shot offered by the kit, so we started with 200hp jetting. After installing the solenoids on a billet Wilson nitrous plate, we made sure to elevate the internal pressure to just over 1,000 psi (bottle temp at 92 degrees).
After minor adjustments to the independent fuel pressure supplied to the nitrous solenoid, the NOS-fed 557 responded with peak numbers of 1,014 hp and 935 lb-ft of torque. Imagine having 1,000 hp at your fingertips after swapping this fire-breather into a light Fox Mustang?
BBF Head Flow Comparison
|Super Cobra Jet||Kaase P51|
Kaase P-51 Cylinder Head Specs
|Intake runner volume||310 cc|
|Exhaust port volume||145 cc|
|Intake valve diameter||2.250 inches|
|Exhaust valve diameter||1.760 inches|