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.