BOSS NINE BUILD

At the end of 2007, long-time Mountain Motor engine master Jon Kaase decided to take “the plunge and build all-new Boss 429 Ford retrofit heads and related parts. I was betting on the fact that there were other Ford enthusiasts out there who wanted these new parts as badly as I did. Although [the parts] have only been out for a short while, I’m happy to say that they’ve been well received and successful in whatever projects they’ve been used.

“The stock Boss 429 parts were a masterpiece for their time but slightly weak and difficult to work on. We made every effort [with the Boss Nine] to fix anything that was troublesome or failure prone.”

Solving the cylinder-block problem was easy. Kaase simply undertook the 429/460 big-block (in iron and aluminum), providing them with cylinder-head oil drains in the correct location. The JKRE plan included using OE 460 head gaskets, so the deck surface of the Boss Nine heads is much thicker than the original dimension to provide the necessary clamping force.

Original Boss 429 Mustangs are rather scarce with just 1,358 produced (859 built in the spring of 1969; 499 more came to life as ’70 models later that summer). The Boss 429 engine was humorously underrated at 375 hp, while it probably made closer to 475 at the flywheel and without the parasitic drag of the accessories. The ports were huge, had poor low-speed velocity, and didn’t begin to show their stuff until the tach was beyond 3500 rpm. Camshaft technology was light years behind the current form. Kaase knew that these two issues had to be addressed for a modern street-driven powerplant that was originally created for the racetrack.

To that end, he spent a lot of time rearranging the insides of the aluminum. Though the intake ports appear to be stock at the entry, they benefit from a revised short-turn radius and a revised approach to the valve seat. The floor of the exhaust-port exit and the valve bowl under the seat were reduced in size. At all times, the quest was to make the Boss Nine heads appear like the OE castings.

Kaase modified the semi-hemi combustion chambers and relocated the spark plugs for resistance to detonation. Size of the combustion chambers has been reduced to 90 cc so that flat-top pistons when fitted in a 460-inch engine will yield a compression ratio of 10.5:1. Further, the stock Boss 429 intake and exhaust manifolds fit the Boss Nine without modification. Moreover, the miracle of modern technology can produce camshafts with enough magic ground into them to puff up torque for low-speed driving and provide a 750- to 800-rpm idle, with duration that builds maximum cylinder pressure and different timing and lift for both valves.

With his usual aplomb, Kaase approached the last area of contention, the wildly disparate rocker-arm system. He incorporated the rocker-mounting saddle in the cylinder-head casting, thus eliminating the mounting block, representing a savings of about $400 when purchasing the rocker-arm set. These items are the product of W.W. Engineering and are the very same that Kaase uses on his 820ci IHRA motors. The exhaust rocker arms, which have a ratio of 1.75:1, were designed to move the pushrods away from the block deck. In keeping with his “budget” approach to this project, Kaase uses Manley stainless steel intake and exhaust valves with common, big-block Chevy-sized 11/16-inch stems.

So what do you get when you apply Boss Nine heads to a 460-521ci short-block? How about an immediate increase of 50 hp as compared to Kaase’s powerful P-51/SCJ heads? Swap these beauties on a 600ci version and the output is 150 additional horsepower. And dig it, ladies and gentlemen — all mechanical delicacies aside, you’d have to go a far piece to impress like the Boss Nine. Check out the following outline for a behind-the-scene Boss Nine build.

A 520 Boss Nine is the most cost-effective version to build simply because the aftermarket has the correct rotating parts (crank, rods, and pistons) in stock and ready to ship. The block arrives with a 4.340-inch bore. The boring process involves eight or nine cutting operations, each cut removing approximately 0.030-inch of metal. Correct bore sizes are finalized by the honing process — three strokes applied with 280-grit stones and three strokes with 400-grit.

Main bearing shells are dripping in oil and pressed into the saddles.

One end of the rear main bearing seal (the first cap to be installed) protrudes beyond the flat of the block to coincide with the appropriately shorter piece in the bearing cap. That way, both ends of the seal are secured within metal, not butted up to it and inviting a leak.

Iron SVO and factory blocks use two-bolt main bearings for the front and rear. They have a hefty ½-inch diameter. Caps 2, 3, and 4 use four bolts each. All aluminum blocks utilize four-bolt main caps.

Assembly lube is applied to the threads and beneath the head of each bolt. Torque is applied in sequence and at 100 lb-ft.

Correct endplay should measure 0.004-0.007-inch. This is determined by the thickness of the vertical walls of the thrust bearings in the center main cap. A dial-gauge is locked in place and then a large screwdriver (or the like) is used to move the assembly back and forth to ascertain the amount of play. This one had 0.006-inch.

Boss Nine readily accepts Diamond custom pistons secured to Scat connecting rods with Trend H-13 piston pins. Bearing caps utilize 12-point, grade-10 bolts and torque to 75 lb-ft. The depth of intake and exhaust valve notches is 0.250- and 0.350-inch, respectively. Intake valves measure 2.30 inches; exhausts are 1.90 inches.

Fel-Pro 1018 head gaskets get a smoosh of sealant top and bottom. Aluminum blocks use studs rather than bolts. Kaase prefers 12-point, grade-10 bolts for iron-block projects and tensions them to 110 lb-ft.

The 385-series Ford block maintains large 2.505-inch bearing journals that lend stability, keeping the cam from flexing at high rpm. This particular engine uses a hydraulic roller tappet version.

Most Boss Nine engines are fitted with a heavy-duty, double-roller cam gear and chain. The crankshaft snout is machined top and bottom for Woodruff keys. Cam timing can be altered by several degrees, plus or minus.

Original oil pumps fitted to high-performance 385-series big-blocks always succumb to vibration and inevitably break. JKRE adds its own device, one that will not fracture and break off under pressure

The wet-sump oiling system relies on a custom sump that features a one-way mesh screen bolted to the sump; a scraper mounted along the top of the mesh; and two one-way trap doors in the sump that operate like check valves, allowing oil to enter but not readily escape.

This engine receives a cam-driven water pump!

Before the hydraulic roller lifters are installed, they are soaked in oil. Sturdy Trend 3/8-inch pushrods accompany them.

As with his 820ci Mountain Motor Pro Stock engines, Kaase employs the same billet rocker arms produced by W.W. Engineering in Dawsonville, Georgia, for the Boss Nine series. They operate with a rocker ratio of 1.75:1.

Carburetor and timing adjustments are being dialed in. Induction choices for this 700hp engine include single-carb, tunnel ram, and two carbs, Hilborn stack fuel injection, or a Wilson 1,388-cfm throttle body and electronic fuel injection. Wilson 1-inch spacer provides an additional 130 cfm.

ADDITIONAL INFO

New 429 Wedge Heads, Too

Jon Kaase Racing Engines, builder of 14 IHRA and NHRA Pro Stock championship engines, has entered the street-performance market with its new P51 aluminum cylinder heads for the Ford 429/460.

A few years ago, Kaase corrected longstanding shortcomings in the original 429/460 cylinder heads, relocated the valves, redesigned the combustion chambers, and reconfigured the intake and exhaust ports. For the first time, the 429 wedge engine exceeded the 350-cfm peak intake flow of the venerable Boss 429. Kaase, in collaboration with Ford, designated the new heads the Super Cobra Jet.

THE NEW P51

In the intervening years and with ambitions to expand into broader markets, including the street-performance arena, Kaase consolidated the gains made in the SCJ heads and continued to refine them. Now, with peak intake flow ratings of around 400 cfm, the new Kaase P51 variants are available directly from the Kaase factory. Even better is their superb midrange flow.

Kaase retained the 72cc combustion chambers, allowing use of pump fuel and experimentation with compression ratios through slightly dished or slightly domed pistons. P51 chambers are fully CNC-machined and contain larger 2.25-inch intake valves. The standard size exhaust valves are retained. The P51 heads function with the original rocker gear, but require longer pushrods because of altered valve geometry. Intake and exhaust port locations are unchanged, so existing intake and exhaust manifolds can be used, if needed.

SOURCE

Jon Kaase Racing Engines
735 W. Winder Industrial Pkwy.
Winder, GA 30680

(770) 307-0241
www.jonkaaseracingengines.com