Steve Magnante's 1001 Mustang Facts. Steve Magnante

      167 New for 1969, Boss 302 and Mach 1 buyers could pay $19.48 for a trunk-mounted spoiler. Because of its plastic construction, the horizontal wing drooped visibly (and embarrassingly) in hot climates. A thicker (and heavier) fiberglass wing was employed for 1970. Because the stock trunk lid support springs were not upgraded, 1970 Mustangs equipped with the trunk spoiler were equipped with a mechanical support rod to prevent finger-nipping from sudden trunk closures. Speaking of plastic, the 1969 models were the first Mustangs to incorporate plastic grilles instead of metal.

      168 Often overlooked, the 1969–1970 body shell came in for numerous dimensional tweaks. The windshield rake angle was increased an extra 2.2 degrees and the fastback roof line was lowered by .9 inch. The altered greenhouse added sleekness but rendered all pre-1969 glass panels non-interchangeable.

      169 The 1969 Mach 1 was Detroit’s first-ever application of body-colored dual racing mirrors on a regular production model. Within a decade, virtually every auto maker on the planet had borrowed the scheme in one form or another.

      170 The (1969-up) Mach 1 recipe deviated from previous Mustang performance models in its inclusion of a standard-issue (no extra cost) luxury interior that included full carpeting, a console, clock, simulated teakwood appliques, bucket seats, and sports steering wheel, all standard issue. Ford’s decision to coddle the passengers in luxury was successful and helped sell 72,458 Mach 1s in 1969 alone (about one in four).

      171 One controversial aspect of the posh Mach 1 package was its inclusion of an additional 50 pounds of insulation and sound deadening material. Consisting of asphalt mats, sprayed-on rubberized body coatings, and fiberglass pads, many devoted drag racers spent hours liberating the dead weight or selected a base SportsRoof or GT model, neither of which carried the baggage. Remember, in a quarter-mile acceleration contest, every 100 pounds shed is equal to .1 second at the finish line. That same tenth is also equal to roughly a full car length at the finish.

      172 Often overlooked, the rear side markers added to the Mustang in 1968 came in two distinct and non-interchangeable varieties. Cars built before approximately February 15, 1968, received rectangular red reflectors set into simple, nearly flush-mounted, body color bezels (as seen on Steve McQueen’s fastback in the movie Bullitt). But in mid-February, a switch was made to much more ornate surface-mounted reflectors set inside chromed metal frames with engraved black perimeters. Two different quarter panel stampings were required for each reflector type, so the revision wasn’t painless for Ford production accountants.

      173 The 1968 Mustang also received new federal front side markers, but unlike the passive red reflectors used at the rear, the trapezoidal clear frosted lenses covered amber bulbs that lit up at night in accordance with federal mandate. Surrounded by bright metal bezels, one might think the mid-February change to the rear reflectors was made to bring design harmony to the front and rear markers. But comparing the second-series rear reflector frames with the front marker frames revealed totally different efforts. A peek through the window of the local Lincoln-Mercury dealer solved the mystery. The same reflector was used on the 1968 Cougar, Comet, and Montego (see Fact No. 153 for more).

       What’s behind the odd two-tone effect seen on the fender and hood graphics of the 1970 Boss 302? Fact No. 174 sheds light on the truth.

      174 The entire 1969 Boss 302 side stripe graphic turned a pearlescent, reflective white when illuminated by headlamps at night, but the same cannot be said of the 1970 Boss 302 graphics. Expanded to embellish the horizontal surfaces of the front fenders and hood, only the vertical markings were rendered in the special reflective 3M tape. The remainder of the graphic consisted of solid, non-reflective material. The result is an odd two-tone effect under certain lighting conditions.

      175 It’s difficult to imagine today, but non-Shelby Mustang buyers had to cough up an additional $54 for a tachometer in the 1967–1970 period, and this included Mach 1s and Bosses. This helps explain why so many 4-speed Mustangs today lack their original engine blocks. In a move calculated to control excessive crankshaft speed (and warranty claims), the 1969 Boss 302 was equipped with a standard Autolite ignition governor set at 6,150 rpm. Oddly, the 1969 Boss 429 did not share this vital ounce of prevention. But as 1969 Boss 429 customers began dropping valves, the 1970 Boss 429 adopted the 302’s ignition cutout unit, also set at 6,150 rpm. A similar unit was installed on 428 Cobra Jets but with a 5,800-rpm limit. Today, lost Autolite governors are available as faithful nonfunctional reproductions (they’re empty cases with no electronics to avoid legal hassles should a faulty unit trigger the loss of an irreplaceable numbers-matching engine).

ENGINE AND DRIVELINE

      176 On the handful of factory-built 1969 and 1970 Mustangs produced with the 351 2-barrel (H code) and optional Shaker hood scoop, Ford inserted a 1-inch-thick aluminum spacer between the cast-iron intake manifold and the carburetor base plate. Without the spacer, the low-rise, dual-plane, 2-barrel intake manifold reduced the total component stack height, causing the Shaker to sit too low in the hood skin cutout.

      177 The Boss 429 1969 LID Mustang concept car (see Fact No. 128) broke the Boss 429’s 4-speed-only transmission recipe. While every one of the 1,358 Boss 429 Mustangs (859 in 1969 and 499 in 1970) sent power into a clutch-controlled Ford Toploader 4-speed manual gearbox, the LID Boss 429 was coupled to a heavy-duty C6 automatic. The LID Mustang existed in the heady realm of factory-built experimental machinery and cannot be included in the normal scheme of things. Its brief existence, however, must be acknowledged.

      178 Ford’s desire to keep a lid on the raucous nature of big-block Mustangs led to the use of single cross-flow mufflers on all 1967–1969 factory dual-exhaust systems (including Shelby and Boss). Although they were often discarded in favor of completely separate piping and a dedicated muffler for each bank of cylinders, faithful restorations must include the somewhat restrictive canister-style muffler fitted sideways between the rear axle and gas tank.

       Mustang dual-exhaust systems were improved dramatically in 1970. See Fact No. 178 for more.

      179 Performance fans cheered in 1970 when Ford eliminated the restrictive cross-flow muffler and switched to more efficient true dual-exhaust plumbing under all high-performance Mustangs. Even though advertised horsepower ratings were unchanged, the reduced back pressure certainly increased power and greatly improved the Mustang’s “street credibility” thanks to a more aggressive burble at idle and a throaty roar at full throttle.

      180 The amount of power gained from the improved 1970 straight-through exhaust system strategy depended upon the engine. Conservative powerplants such as the 300-hp (rated) 351 Windsor and Cleveland 4-barrel likely saw an extra 5 to 10 hp. The 335-hp (again, rated) 428 CJ and CJ-R appreciated the improved plumbing even more and responded with an extra 15 hp. But the Boss 302 and Boss 429 saw the greatest gains. Born to breathe and rev (the 302 was fitted with a 6,150-rpm limiter, because it was apt to spin high), the 1969 transverse exhaust was particularly stifling. Again, although no advertised claims were made (Boss 302 = 290 hp, Boss 429 = 375 hp), the true duals are said to have been worth 25 to 30 hp on these rev-happy stormers.

      181 Before the Fox body Mustang gave it a high-performance image makeover as the 5.0 HO, the 302 small-block was marketed as a bland work horse. There were two exceptions, the mighty 1969–1970 Boss 302 and the often overlooked 1968-only J-code. While the Boss 302 truly was a detuned racing engine with unique canted valvehe-ads, four-bolt main caps, and numerous ultra-duty parts, the J-code arrived in mid-1968 to fill the spot vacated by the A-code 225-hp 289 of 1965–1967. Rated at 230 hp, the J-code inhaled through a single 441-cfm Autolite 4300 series 4-barrel carburetor but shared the same single exhaust system as its 210-hp 2-barrel 302 cousin (engine code F). The Boss 302 and J-code