Last time we discussed the development of the Rochester fuel injection system and the changes that took place from its introduction in 1957 through the 1959 model year. In Part 2 we’ll trace the nuances and specific differences of the 1960-65 fuel injection systems.

01: 1960-61 #7017200 fuel injection unit viewed from driver’s side.

Rochester Fuel Injection Evolution 1960-61
      The #7017200 and #7017250 units used in 1961 were carried over from the 1960 model year. 1960 250HP and 1961 275HP engines used #7017200 units, and 1960 290HP and 1961 315HP engines (some possible) used units #7017250.
     In late 1960 a newer plenum design with improved airflow was introduced. This unit had a smooth top with no ribs and was #7017320. This continued through 1961 on high horsepower cars.

02: 1960-61 #7017200 unit, passenger side view. Note pen showing position of the stamped "202" on the #7017200 fuel meter.

     The air meter and fuel meter on this unit are the same as in #7017250.
     Also for 1961, a #7017310 unit with a smooth top plenum was released for 275HP cars. This unit is very scarce today. All 1960 and later units had internal siphon breakers in the fuel meters. The choke for 1957-61 units was mounted on the top of the air meter near the Venturi signal passage.

03: 1960-61#7017200 unit with close-up of "202" stamping

1962
      Beginning with the 1962-model year, no low horsepower fuel injection options were offered. Two new fuel injection units, the #7017355 and the #7017360, were used on RPO 582, the 360-horsepower engine option. These fuel injection units differed from previous models primarily in the design of the cold enrichment system. The newly designed cold enrichment and diffuser cone assembly incorporated an almost conventional blade-type choke valve which eliminated the complex valving of cold enrichment systems found on previous models. The electrically heated thermostatic coil, mounted on the air meter inlet, now positioned this choke valve to provide necessary venturi signal "boost" for fuel enrichment.

04: 1960-61 #70172000 unit. Note pointer indicating stamped number on #7017200 air meter mounting flange.

     The fuel meter design was unchanged except for a redesign of the metering valve, use of a poppet-type valve in place of the spill plunger and relocation of the cranking signal valve to the cover of the power enrichment diaphragm. With the newly designed cold enrichment housing, vacuum for power enrichment was now drawn directly from the injector intake manifold. The new location of the cranking signal valve virtually eliminated the possibility of its failure due to back- fire.

09: 1960-61 #7017320 fuel meter assembly. Pen is pointing to stamped number "252" location. Note fuel meter foil ID tag.

      The two-line system with a cranking signal valve was replaced later with a one-line system without a cranking signal valve. This unit number was #7017380. For cranking enrichment, a microswitch and a fuel bypass solenoid were used. The solenoid was in-line between the fuel meter fuel inlet and the fuel spider and provided extra fuel at engine supply pressure directly to the nozzles.

11: 1960-61 #7017320 air meter. Pen is pointing to location of stamped ID number "251."

     The Rochester fuel injection system had evolved steadily since its inception in 1957 and had become quite reliable when it was cancelled in 1965. There were several reasons for its demise, primary being the introduction of the new Mark IV 396 cubic inch engine. The big block offered more horsepower and torque than the fuel injected small block and was substantially cheaper. Additionally, fuel injection had always suffered in popularity because Chevrolet Service personnel didn’t like or understand the system, a problem recognized from the very beginning.