Follow the build up of the 589c.i. Kaase Boss Nine Mustang.
Jon Kaase's 2008 Ford Mustang - Blue Crescent Beheader
By Ro McGonegal
Photography by Robert McGaffin
have always wanted a Boss 429 Mustang because I consider it to be
Ford's masterpiece of engineering. The problem is, considering their
present value [approximately $500K], I was as far away from being able
to afford one in 1969 as I am today. If I could buy an original, it
would be far too valuable to drive. With the release of our Boss Hemi engine
parts, the next logical step was to build our own version,
rationalizing that a complete running car would showcase the new parts
and create a new market for our parts sales," said the gleeful Jon
"Let's be honest here. I wanted
this car! I want to drive it home and give my family and neighbors a
ride. Most of them think I have a garage that does quick oil changes.
They have no idea. I hadn't driven anything with over 360hp since 1974.
With 800 ft-lbs of torque and 900 hp, this car is a real handful."
were yakking with Jon at the recent PRI show about the black beast in
his booth. Then the thread wound into a trip we'd made to his old shop
a dozen years past. We had gone there to document the building of an
812-inch IHRA Pro Stock motor. Forgot what it made, something like
1,400 on the motor. Kaase said that times have changed, drastically,
and that same configuration outfitted with the latest parts would put
out at least 1,900. We'll come back to this in a minute.
at the Boss Nine Mustang. Kaase's vision was based on a stock-appearing
car, one that you would buy from a dealer with the biggest motor
available. It was rated at a paltry 375 hp. Kaase's version makes 900.
In the day, the 1969-70 Boss 429 came with 7-inch Magnum 500 rims and
F60 Goodyear Polyglas GT rubber, and perhaps the most arresting thing
about it was the distinct lack of stripes, black-out trim, wheel or
rocker panel moldings, or chrome exhaust tips.
All it said was "Boss 429" on the fenders, and it carried a functional
hood scoop that practically disappeared when the body wore dark livery.
Kaase's Boss Nine fairly reeks that aura and looks for all the world
like it just rolled off the Kar Kraft (Brighton, Michigan) "assembly"
line, modern Magnum rims and all.
that image comes from a new Mustang that Kaase bought from B.F. Evans
Ford in Livermore, Kentucky. It had but 180 miles on the odometer, and
only because Evans' guys drove it to Nashville, where Kaase's guys
loaded it on a trailer for the final miles home. All the build tags and
stickers are still in place, adding to the dj vu mystique. "It was
worth it because it's new and it's a pleasure to work on, no dirt, oil,
or road gunk," quipped the low-key Kaase.
biggest obstacle for Kar Kraft was that skinny space between the shock
towers, a place never meant for an engine with the girth of the Boss
(see "Total Performance," p. 44). Their techs had to cut out, rebuild,
and relocate the towers to make room for the big Blue Crescent
(semi-hemispherical combustion chambers) cylinder heads, and with
little space to spare even at that. Kar Kraft also lowered the
suspension by about an inch, using control arms and spindles specific
to the Boss 429. We asked Jon about how the Boss Nine fit in that
modern engine compartment. He smiled, Cheshire cat-like. "You could say
it just sort of fell in there. We didn't have to trim, cut, or rebuild
anything for it to take the motor. We didn't even have to take the hood
Then: "I should have measured the
stock engine crank centerline at the front, with respect to the sides.
The tailshaft and rear crossmember measured to be in the centerline of
and the pinion is also centered between the wheels. The thing is, I
remember the valve covers to be unequal distances from the shock
towers, offset to the right. Is the engine in these [new] cars at an
angle? With the Boss engine in place, the tailshaft is centered and the
valve covers are closer to the right, just like stock.
is a natural for the Boss Hemi swap. There is plenty of room between
the shock towers, enough room for headers [you can reach past them with
your hand], and enough room between the accessory drives and the
radiator. The hood needs no modification for the air filter. It's
close, but the right filter assembly will fit. A stock rear sump Moroso
pan fits over the steering and crossmember perfectly. The cooling
system is completely stock. All we did was space the bottom of the core
outward an inch or so, but the top of the radiator is in the stock
Kaase stripped it down and
installed a mock-up engine, then sent it to fabricator pal Chuck
Lawrence in Hiram, Georgia, for motor mounts and headers. Back at Jon's
shop, they built and dyno tested the 589 and installed it with the
clutch, transmission, and driveshaft. It went over to Lawrence's for
the close-up work--hoses, wiring, gauges, and the rest of the finish
Kaase: "The front drive is from
Billet Specialties. It comes with a billet front cover, which has extra
bosses for attaching the accessories and brackets. It comes with the
front cover, water pump, power
steering pump, an alternator, A/C compressor, and all the pulleys and
brackets. Nothing bolts to the heads. As complicated as it looks, it
only took an hour to completely assemble it. Like any good racers, we
threw the instructions out and just winged it. I was really impressed
with the quality and fit of this assembly."
the Boss 302 was created to champion small-block performance and to rub
fenders with the Chevrolet Z28 in the Trans Am series, in the big-block
world, the Boss 429 was really a homologation special required for
legality in NASCAR. Production for '69 was 859 units (including two
Boss 429 Cougars). In '70, the total was but 499. Automatic
transmission and air conditioning were not offered, but at least it had
an engine oil cooler and the battery
was moved to the trunk, largely to free up space in the motor room.
Well, they still don't race Mustangs in NASCAR, so how come it wound up
in one instead of the obvious Torino? Sorry, we can only guess at the
back story on this one, but Ford marketers figured heavily on boosting
the Mustang's image, so that's the way it was.
remarks about the efficacy of modern speed parts made us think. The
Boss 429 had huge ports and a marginal camshaft that really didn't take
effect until the engine was really winding up, so low-speed torque
pretty much sucked. His Boss Nine heads (which will fit on any 429-460
block) have holes just as large, but the advance in camshaft phasing
and ignition technology "adjust" for these ancient and potential
shortcomings. The same goes for the completely stock suspension. When
the weak stuff breaks, they will amend the woe with stronger stuff.
No matter how careful I am with the throttle, and I'm talking
Third and Fourth gear now, it literally wants to rip the tires
off (laughs). Now that I've felt this thing, realistically, a 466-inch
Boss Hemi would be about right for this car, but, as they say, anything
worth doing is worth doing in excess."
Can we get an AMEN!
a work in progress, the Mustang chassis/suspension is bone stock. The
Boss Nine is equipped with latter-day 18-inch American Muscle Magnum
500 wheels and thick Pirelli PZero Rosso rubber, but the motor has
enough moxie to break 'em in Fourth gear.
as slick as a moleskin biscuit, the Boss Nine has every bit of its
assembly line interior. Colorful it ain't; functional it is. Note the
just-the-right-height Hurst gear changer.
Performance supplied the blast-shield/bellhousing and the Viperized
T56. Kaase made the crossmember. The McLeod clutch assembly is
twin-disc on an 11-inch steel flywheel.
cars had a working hood scoop. Kaase wanted to stay away from that, so
he used a NASCAR-flavored BSR air cleaner and bottom plate that drops
the whole assembly cleanly away from the underside of the hood. Big
Boss is nearly 600 ci large. Kaase's pal Chuck Lawrence did all the
wiring and considerable finessing needed to make it all work.
'08 Ford Mustang
John Kaase • Winder, GA
Vehicle weight w/driver: 3,800 pounds
Ford displacing 589 cubic inches
(4.627 bore x 4.375 stroke)
The day we drove it home from
KY Thanks to Lem Evans, (B F Evans Ford)
Lots of parts. It’s a good thing we don’t have to remember where they go. We’re just getting started!
Our day’s trophy. Anybody need a new 3-valve, 4.6?
Here we are going to Chuck Lawrence’s for headers and motor mounts. (90 miles)
There’s more header and shock tower room than a 1969 car.
3” Granatelli stainless exhaust, from the collectors back.
These are Chuck’s 2-1/8” x 3-1/2” headers, before coating
This is the 589” Boss Hemi. It’s 4.627” x 4.375”stroke. The Diamond pistons were made for 10.5 to 1. The rods are Oliver, 6.8” The reason the lifter bores are bushed, is because they were already .937” when we traded for it. We couldn’t find a Boss Hemi “Z” bar lifter with a .937 body, so we had to bore it and bush it down to .904. Crane makes a premium lifter with a “Z”bar at .904”.
Our new Boss Nine heads, unported.
This is with the 251-251, 110 degree roller. Very street able at this cubic inch.
These last 2 dyno sheets are with a 273-280, 109 degree roller.
The front drive is from Billet Specialties. It comes with a billet front cover, which has extra bosses for attaching the accessories and brackets. It comes with the front cover, water pump, power steering pump,alternator, A/C compressor, and all the pulleys, brackets, etc.. Nothing bolts to the heads. As complicated as it looks, it only took an hour to completely assemble it. Like any good racer, we threw the instructions out and just winged it. I was really impressed with the quality and fit of this assembly.
We have never had the hood off.
OK, so here's the deal on the wheels & tires. I spent quite a lot of time online researching tires and wheels. I wanted wheels that were similar to the original Boss 9, 1969 wheels. These are pretty close. The front is 9 x 18, and the rear is 10 x 18.These came from a place in
PA., called Americanmuscle.com.(found it online)
The tires came from Tirerack.com, also found it online. I learned a lot about tires and sizes this week. I wanted tires that were at least as tall as the original P235/55ZR17's. Also I wanted a Y or (Y) speed rating. A (Y) is one of the highest at 186+ mph. Along with that, I wanted a 255/45/18 for the front, and a 285/40/18 for the rear. With these speed ratings and sizes, the selections were getting small. Goodyear had the front but not the rear sizes. B F Goodridge had the speed ratings and the right sizes, but the tread looked terrible to me. Sort of like a mud or snow tread. I'm sure it would have worked fine, it just looked like hell. It came down to Bridgestone, Michelin, or Pirelli. I just couldn't put a 149 mph tire on a 200 mph car. Also around here when it rains there's lots of standing water on the roads, and I see crashes all the time when the storms hit. I couldn't put drag radials on it for this reason. I think the Pirelli's are a good tire and they won't come apart if the car ever sees some high speed.