Beginning with the 1968 model year, all vehicles sold in the USA were required to meet new federal standards for hydrocarbon (HC) and carbon monoxide (CO) emissions. One of the more effective ways to reduce these pollutants was through the use of a thermal reactor (thermactor) system. Thermactors inject pressurized air immediately downstream of the exhaust valve in order to continue the combustion reaction to reduce the amount of HC and CO at the tailpipe.
This article was written by Chris Teeling.
Big block (390 & 428 CJ) Mustangs and Cougars produced after March 1968 were built with reinforced front shock towers. The reinforcements were added due to shock tower cracking issues that had resulted in warranty issues for Ford and Mercury after the introduction of the 390 engines in 1967.
Ford describes the part used to support the rear end pinion gear as the "driving pinion bearing retainer and bearing cup assembly", identified by basic part number 4614. It's more commonly called a "pinion support". The pinion support used on all 1968 - 1970 Ford Mustangs equipped with a 9" ring gear and 31-spline rear axle shafts (which just so happens to include Mustangs equipped with 428 CJ and SCJ engines) is often called the "Daytona" pinion support.
The transmission oil filler tube assembly used with Ford's C6 automatic transmission is identified by basic part number 7A228. The transmission oil level indicator (dip stick) fits inside the filler tube. The tube includes a mounting bracket to secure the upper end of the tube to the back of the engine, and an o-ring at the bottom to seal the area where it's inserted into the transmission. Two different tubes were used during the course of 1968 - 1970 Mustang 428 CJ production.
Classic Mustang speedometers are spun by a steel cable that runs from the transmission to the speedometer. The rate at which the speedometer spins is determined by a drive gear that is either part of the transmission output shaft (in the case of automatic transmissions) or physically attached to the transmission output shaft (in the case of manual transmissions) and a driven gear that's attached to the end of the speedometer cable.
The 428 SCJ engine required an engine oil cooler that was mounted in front of the radiator on the driver's side of the radiator core support. This required moving the driver's side horn to the passenger side of the radiator core support to make room for the oil cooler. The relocated horns were usually secured to the core support using a reinforcement plate that was mounted on the back side of the core support.
Ford crankshaft damper spacers are identified by basic part number 6359. This part fits over the front end of the crankshaft snout and fills the space between the crankshaft vibration damper and the timing cover. The 428 Cobra Jet and Super Cobra Jet spacers are made of steel and were typically unpainted when installed.
Ford carburetor spacers are identified by basic part number 9A589. The spacers used on the 428 CJ and SCJ engine are made of a black plastic material that is similar to bakelite. The spacers are not marked with an engineering number.
Ford engine oil level indicators (sometimes referred to as a dip stick or dipstick) are identified by basic part number 6750. Ford used two different service part numbers for the indicators used with the 428 CJ and SCJ engine.
Ford connecting rods are identified by basic part number 6200. Made of forged steel, the rods used in the 428 Cobra Jet and Super Cobra Jet engines measure 6.488 inches in length from center to center. Part of the engine's reciprocating assembly, connecting rods connect the pistons to the crankshaft.