834hp 429 Boss Ford Engine Build - 834HP Kaase Bos

The only way this monster would look better is between the fenders on a hot street car with big tires. This particular engine is going into a real '69 NASCAR Talladega stock car owned by Brad Smith.

The only way this monster would look better is between the fenders on a hot street car wit

Jon Kaase drank the Ford blue Kool-Aid a long time ago. His association with the Blue Oval goes back to his NHRA Super Stock days with a 428 Cobra Jet Mustang in the early '70s and has progressed through a stint as crew chief for the legendary Dyno Don Nicholson in NHRA Pro Stock. Kaase (pronounced kah-zee) is best known now for his engines that have won an astonishing 12 straight IHRA Pro Stock World Championships. He's also put a hammerlock on the Engine Masters competition, winning that event four times. So it's safe to say that Kaase knows his way around big-block Fords. So in a flash of brilliance he decided what the world needed was a new Boss 429 head.

While it may appear that Kaase came up with the idea and the heads just fell out of the sky a week later, the reality is that the gestation period took the better part of 18 months. To make these heads nestle into the Kaase scheme, they had to bolt on to a standard 429/460 block.

Car Craft was lucky enough to be among the first tier recipients of a set of finished castings. We planned to enlist fellow Ford fan Jim Grubbs, owner of Jim Grubbs Motorsports (JGM) to help us through this buildup, but he volunteered before we had a chance to ask. Except for the funny valve reliefs on the pistons, the short-block could easily be mistaken for a typical wedge buildup. Once we had all the parts, the only real custom work was a little grinding on the block to clear the No. 4 exhaust pushrod.

Once the engine came together, the final result underscored the investment with an amazing dyno session at JGM that had industrial complex neighbors stopping by to ask what race motor was up on the dyno. Unlike most dyno sessions that demand tremendous effort to squeeze that last ounce of power from the engine, once JGM's Jeff Latimer set the timing at 34 degrees, the only effort was to set the hot lash. The Holley Dominator Ultra carb delivered a great fuel curve right out of the box, and the massively cammed Boss Nine beast cranked out an astonishing 834 hp at a singing 7,100 rpm. The best part is that Kaase says with a bigger carb and perhaps some stiffer pushrods, we could easily make a bunch more power. The days of easy horsepower have arrived. It may not be cheap, but it most definitely is easy.

Look closely and you'll notice that our first-choice 4.500-stroke Scat crank pulled virtually the entire piston skirt out of the bottom of the cylinder sleeve. This obviously was not going to work, and since we already had the pistons, we elected to move down to a 4.300-inch-stroke Scat crank and 0.100-inch-longer rods.

Look closely and you'll notice that our first-choice 4.500-stroke Scat crank pulled virtua

Displacement Lessons
We knew Kaase's heads would be barn burners even before we got the first castings. This meant the massive flow numbers would support a big-inch engine. So right out of the box, we found that Scat builds a 4.50-inch stroke crank that will bolt right into a stock 429/460 block. A quick run through the calculator revealed that we could build a monstrous 545ci motor with bolt-on parts. We packaged this long-arm crank with a set of 6.700-inch Scat rods with a custom Kaase-spec'd Diamond piston but then discovered that the long arm also pulled the piston almost completely out of the bore at bottom dead center. This clearly wouldn't work, so we had to regroup. With help from Scat owner Tom Lieb, we were able to assemble a 0.200-inch-shorter crank at 4.300 with a 0.100-inch-longer connecting rod at 6.800 and balance the assembly to match the previous system. So instead of a thumpin' 545ci Ford, we ended up with an only slightly smaller 521ci beast. Just for the record, we learned later from Kaase that A460 and Eliminator castings from Ford Racing and later-production '79 (D9 casting number) blocks all have 0.250-inch-longer cylinder sleeves that would easily accommodate the longer 4.500-inch stroke. Next time we'll add the longer arm. It makes you wonder what a 454ci wedge motor with a set of Kaase's P-51 heads would make. Those heads are a bit more affordable and flow 400 cfm at 0.700-inch lift.

Comp mechanical roller Cam

1.

Lash is 0.024/0.026-inch intake and exhaust. *Note: Gross lift is before lash. To obtain net lift, subtract lash plus any measured valvetrain deflection. It is not unusual to experience perhaps 0.020 inch of deflection, especially with these long pushrods and rocker arms.

1. Kaase also spec'd the Comp solid roller camshaft, but you'll only find it in the Comp Cams specialty lobe catalog. Kaase chose the TK- and HXL-series intake and exhaust lobes. Comp's description lists the TK series as "intense." These are lobes designed for drag racing, but Kaase thinks they would survive on the street and not be too abusive to the valvesprings.

Boss Nine Heads
This is where it gets fun. Back in 1969, Ford was all about stuffing giant ports into many of its engines. Airflow was king, and engines like the Boss 302, 351 Cleveland 4V, Boss 429, and the Tunnel Port 427 were headliners. While automotive performance history may have shunned those efforts, we think the ports weren't necessarily too big; the engines weren't nearly big enough. With new Boss Nine Kaase heads blessed with tons of airflow, it became a moral imperative to punch up the displacement to 21st century dimensions.

Kaase focused on eliminating all the factory quirks that have always stood in the way of building a reasonable Boss motor. Those factory O-rings had to go, as did the oddball separate oiling passages through the head as opposed to lubing through the pushrods. He also managed to ensure his heads could return most of the oil back to the engine through production channels. Other limitations Kaase faced included maintaining all the factory intake and exhaust port positions along with valve angles and all the classic external visual cues such as the undulating valve covers. Even the combustion chambers are similar to the original semihemispherical shape. That description comes from the twin flats or quench areas found on opposite sides of the chamber that help create turbulence in the chamber, which is something a true Hemi has trouble creating. A better description of the chamber might be more like a wedge with opposing angle valves. Kaase then tweaks the chambers with full CNC machining. The castings also incorporate pedestals for those Mississippi-bridge-like exhaust and intake rocker arms, which defrays some of the cost of the W. W. Engineering 1.75:1 rocker system. If you happen to own a set of original Boss 429 valve covers or intake/exhaust manifolds, those parts will also bolt right up to the new Boss Nines.

Flow Chart

Here's where massive area delivers huge flow numbers. Partly due to the 2.300- inch intake valve, the intake ports flow some very serious numbers. Yes, the 409 cfm at 0.600-inch lift is impressive, but do not overlook the equally impressive 308 cfm at 0.400-inch lift. Remember, the intake valve resides at max lift only once but achieves midlift numbers twice. Intake port velocity will suffer with a cross-sectional area that is closer to a Pro Mod drag race engine than for a streeter, but there's no denying the huge flow numbers. The exhaust ports do equally well to deliver a decent exhaust-to-intake (E/I) percentage of 70 percent.

Makin' Power
During the warm-up, our 521ci Boss just sounded angry. We've heard hundreds of race engines, so the rough idle and shaking on the dyno wasn't unusual. We were standing on the other side of a concrete wall looking through reinforced glass, but the combination of that big cam and sewer-pipe-sized 21/4-inch open headers just made this engine sound even more lethal. After a mere seven pulls, we had our peak at 834 hp, and once the euphoria subsided, we investigated the power numbers more closely. Most normally aspirated engines that make really big power tend to be very peaky, meaning the rpm spread between peak torque and peak horsepower is usually very narrow. But Kaase's combo managed to spread the twin peaks by an amazing 2,100 rpm compared with more common spreads of 1,500 rpm.

It would have been fun to see how much a larger 1,150-cfm Dominator carburetor would have worked. Plus, keep in mind that these heads and the intake manifold are right out of the box. Even really good castings can benefit from mild tune-ups, so we don't doubt that with a few tweaks, our Kaase Boss could easily reach the 900hp mark. For us, 834 is a personal best for a normally aspirated engine generating an impressive 1.6 hp per cubic inch. If nothing else, all this power will make for an outstanding top-end charge on the dragstrip.

Power Numbers

PARTS LIST