Eric English
February 3, 2010
Photos By: Jim Smart

Kaase Boss Nine
Big news for classic Ford enthusiasts occurred in the last year, as Jon Kaase Racing Engines released brand-new Boss 429 cylinder heads, rocker arms, valve covers, and intake manifolds. Unless you've been hiding under a rock for the last 20 years, you'll recognize Kaase's name as one of the preeminent big-block Ford builders, specializing in the mountain motors of IHRA Pro Stock. Kaase engines can be credited with more than a dozen IHRA championships, but Kaase began the hard-core phase of his Ford experience in 1977 working for one of the greats, Dyno Don Nicholson. More recently, he's received positive ink for winning the Engine Masters Challenge four times (2003, 2004, 2008, and 2009), the most recent win coming via a 400-inch Cleveland.

The genesis for the new Boss Nine parts came from Kaase's desire to build a Boss 429-based engine for the Challenge. "The problem was that original Boss parts are hugely expensive and relatively fragile as well," says Kaase. From the start, the idea was to build parts that could be used as replacements for original Boss 429 components, or used to easily build a Boss from scratch. The latter wasn't the case prior to the new parts, as a Boss block was almost a requirement in order to use the heads-if you could find them. Boss blocks utilize unique oil galleries and drain holes which match those in the Boss heads, lubricating the rocker assemblies through the rocker stands. Non-Boss 429/460 blocks don't have these features, as the rocker system on conventional 385-series big-blocks is oiled through the pushrods. While tapping into the lifter oil gallery on a standard block, and running plumbing in the lifter valley to the Boss head oil galleries is technically possible, and has been done, there are additional issues to overcome. Clearance problems with a standard block are generated by the Boss' steeply angled exhaust pushrods as well.

A far better option are Kaase's new Boss Nine heads, which, while stock-appearing from the outside, are revised in ways that allow them to be easily used on all 429/460 blocks. It's a simple bolt-on operation. Also revised are the CNC-machined combustion chambers-now more detonation resistant, and smaller to allow reasonable compression with flat-top pistons. More important changes were incorporated into the intake- and exhaust-port designs, as well as the rocker-arm geometry. Actually, the entire rocker system is greatly improved over original, and is specific to the Kaase heads-meaning no interchange with the original Boss 429 rocker system.

All other parts do interchange however, meaning you can run a Kaase intake on stock heads, and so forth. You could even bolt stock exhaust manifolds to the new heads, whereupon the "Modified" part of us will ask, "why let 400cfm intake/300cfm exhaust flow potential go to waste?" Throw a set of headers on her, slip in a stout cam, and let it rip! In reality, there is probably a market for folks who need a set of heads for their otherwise-stock Boss 429 Mustang, but we look forward to seeing what people do with the new Kaase parts to really take advantage of their potential. How about a NASCAR Torino clone? How about a Pro Stock Maverick?

Kaase Cylinder Head
Rocker stands aren't used on the new Kaase heads as they were originally, rather the new Boss Nine head has a cast in boss that does away with stands all together. The exhaust rocker is slightly longer, taking some angle out of the pushrod, while also moving the pushrod away from the block deck-avoiding a previously mentioned pitfall of using original Boss 429 heads on a standard block. Another benefit of the revised pushrod angle is reduced side load on the lifter bore, a real advantage if running a solid roller cam with lots of spring pressure.

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