The 4.0 inch Bore Family- 1962 to 1998
The 302 continued…:
For 1967 the 302 engine has a high rise aluminum cast intake used for the first time on the Z/28-this is the same intake manifold again used for the LT-1 350 Corvette for ’69 as well as from 1970 for the Z/28 but the ’73 model year the Z/28 returns to the Q-jet carburetor. The exhaust manifolds for these Camaro’s are more restrictive than the Corvettes is to allow clearance of the Camaro’s front chassis cross member. For ’67 and ’68 this model Z/28 has a unique chromed oil dip stick tube as well as chromed rocker covers showing no Chevy and no engine size or any other logo stamped into the covers. This package is completed with a chromed drop-base open element air cleaner sitting top of the Holly secondary four barrel carburetor. This version, for faster and cleaner warm-ups, also sports a separated exhaust port crossover with a heated well-choke coil. The single point/lobe distributer has been specifically developed to reduce point-bounce at higher RPM while the vacuum diaphragm advances the ignition timing at an idle and at lower RPM to help reduce fuel consumptions as well as emissions. The water-pump and the harmonic balancer pulleys are deep grooved to enhance belt retention at higher RPM, as is the power steering pulley if so equipped. The 302 has the same finned cast aluminum rocker covers as the LT-1 350 Corvette engine. A conservative rating for this 302 at 5800 RPM is 290 hp (216 kW) with 290 ft-lb of torque at 4800 RPM. The actual out-put however, with a production 11:1 compression ratio is closer to 376 hp (280 kW) when the engine is ordered with the 1.625 inch X 3.00 secondary tubular headers which came in the trunk from the factory. The last year for the factory headers is 1968 and the headers are slightly larger with the 1.750 inch primaries by 3.00 secondary tubular pipes. An original factory Z/28 for 1968 equipped with the close ratio transmission, transistorized ignition (an option), headers, and the factory cold air hood induction can do the quarter mile in 12.9 seconds reaching 108 mph in the process equipped with street tires.
The 1967 Trans-Am racing season with Chevy using their four barrel induction system the units were producing more horse power than the other manufacturers with their eight barrel systems. For 1968 Chevy kicks it up a notch with the newly developed aluminum intake-manifold package which integrates two holly four barrel 600cfm mechanical secondary carburetors for the Trans-Am race series. This manifold is available only across the counter at Chevy dealers but only as an off-road or racing part. Add to it the Chevrolet off road cam and these two items will effectively boosts the horsepower of a stock 302 from 360 to around 400. Just to conform to emissions regulations in the U.S.-starting in 1967, Chevy’s used the PVC or positive crankcase ventilation system, as well, incorporated full throttle crankcase pressure venting to the air intake which effectively burns the vapors. The racing versions of the 302 produce up to 465 hp using ported heads, high pressure valve springs, roller rocker arms, the 754 2nd design road racing camshaft and the two four barrel carburetors. For 1967/68 the cowl induction uses an enclosed air cleaner assembly with ducting from the passenger side and into the firewall just above the heater core. A hood for the cowl induction was available for the ZL-2 models in ’69 for both the single and the double four barrel versions. This cowl induction is sealed to the air filter base from a vent in the center of the hood at the base of the windshield providing a stable source of cool, dense, high pressure air to the combustion chamber and assuring maximum power. Your Chevy dealer in’67 could also supply a magnetic-pulse Delco transistor-ignition ball bearing distributor which provides a stronger spark with higher stability than the breaker point ignition. This performance distributor is for the 302 but would also fit the L88 Corvette 427. Any part used in SCCA trans-Am racing had to be readily available from an authorized dealer and for anyone who wanted to use it. continued…