When Chevrolet released the 305 CID V8 for the 1976 model year, no one including Chevrolet would have imagined it would become one of the hottest performance V8s of the 1980s. The 305 V8 which was a member of Chevrolet’s small-block V8 family had only three main purposes back in 1976 – to provide smooth acceleration, good reliability, and good fuel efficiency. On these three accounts it was a success. It was rated 140 or 145 horsepower depending on which 1976 car model it was ordered with and its only induction system was a Rochester 2-bbl carburetor. It was the successor to Chevrolet’s small-block 307 CID V8 which was a budget V8 that only was equipped with a 2-bbl carburetor and never produced more than 200 gross horsepower and had an output as low as 115 net horsepower. The gas-sipping 307 had a short life span from 1968 to 1973. The 305 soon after its introduction was available in many different GM makes and models.
There was a reason why most auto enthusiasts would have never envisioned the 305 ever being a performance motor back when it was first released. The 305 had a very small bore of 3.736 inches which was even smaller than the 3.875 inch bore of the 307 V8 (the 307 used the same bore as the small-block 283). The 305’s bore was even smaller than the 3.75 inch bore of the 1955-1957 265 CID V8 which was the first small-block Chevrolet V8. The small-block Chevrolet 302, 327, and 350 CID V8s all share the same large bore of 4.000 inches. The advantage of a large bore is it makes much better use of high performance cylinder heads. Generally a larger bore V8 engine with a good set of cylinder heads will rev higher on the rpm range than a similar displacement V8 with a smaller bore and longer stroke. On the surface the 305 (5.0 liter) V8 would seem to be an equal to its big competitor during the 1980s, the Ford 302 (5.0 liter V8). However Ford’s 302 had a large bore and very short stroke – 4.004 inch bore and 3.00 inch stroke – giving it a much better potential when aftermarket high performance parts were added versus the 3.736 inch bore and 3.48 inch stroke 305.
It was not until the 1982 model year when GM’s new corporate engine policy took effect, that the 305 then referred to as the 5.0 liter V8, became GM’s most popular V8. The 145 horsepower and 240 lb-ft of torque LG4 4-bbl 5.0 liter V8 was used in many of GM’s 1982 cars. Even the 1982 Chevrolet Camaro Z28 and 1982 Pontiac Trans Am (GM’s performance F-bodies) used the LG4 as their standard engine. And it was 1982 that marked the first year the 305 became a performance engine. As an optional engine on the Z28 and Trans Am, Chevrolet released a thicker wall version of the 305 block that had other performance upgrades – the result was the performance oriented LU5 5.0 liter Cross-Fire Injection V8 (a dual throttle body fuel injection system) which was rated at 165 horsepower and 240 lb-ft of torque. 165 horsepower seems paltry by today’s standards when even many 4-cylinder motors today exceed this horsepower figure, however thirty years ago 165 horsepower was more than most V8s produced during this time period. This was an era when most V8 produced less than 150 horsepower and anything that produced more was a performance motor. As an example the 1982 Ford Mustang GT with its (2-bbl) 5.0 liter (302 CID) H.O. V8 produced 157 horsepower and 240 lb-ft of torque.
The LU5 5.0 liter Cross-Fire Injection V8, used the Corvette’s L83 5.7 (350 CID) Cross-Fire Injection V8’s high-performance cam which gave the LU5 a very high compression ratio (by 1982 standards) of 9.5:1. In 1983 the advertised horsepower rating of the LU5 increased to 175 horsepower and torque increased 250 lb-ft. One of the problems with the LU5 was the aluminum intake manifold which handled the flow from dual throttle body injection (TBI) units had a maximum flow of only 475 cfm in order to meet emissions regulations (the Corvette L83 used the same intake manifold). Chevrolet engine engineers could have offered a higher flow intake manifold to increase the LU5’s horsepower however it instead to chose to replace the LU5 with another high performance 305 – the L69 5.0 liter H.O. V8 – the H.O. stood for High Output. The L69 used the fortified LU5 305 engine block, LU5/L83 high performance cam, and LU5 cylinder heads. The difference was Chevrolet with the L69 replaced the LU5’s induction system with a performance tweaked computer controlled Rochester Quadrajet (750 cfm) 4-bbl and an aluminum intake manifold. The L69 had the LU5’s 9.5:1 compression ratio which was much higher than the LG4 4-bbl 305’s 8.6:1 compression ratio. However the L69 had a new knock sensor which was something the LU5 unfortunately didn’t have. With a 9.5:1 compression ratio both the LU5 and L69 required at least 91 octane fuel – the L69’s knock sensor would automatically retard ignition timing preventing engine pinging and knocking if anything less than 91 octane was used.
During the middle of the 1983 model year, Chevrolet debuted the L69 in a new performance offering the Monte Carlo SS (the resurrection of the early 1970s Monte Carlo SS). When it debuted in the Monte Carlo SS, Chevrolet initially advertised the L69 as producing 175 horsepower and 240 lb-ft of torque. This rating was underrated more than likely for the purpose of not stealing sales from the (175 horsepower) 1983 LU5 Camaro Z28. Motor Trend magazine (April 1983) when it test drove a 1983 Monte Carlo SS referred to it as having 175 horsepower in the body of the article, but listed the SS’s L69 under the article’s "specifications" section as having 190 horsepower which was a more accurate figure. Nevertheless the L69 powered Monte Carlo SS was faster than the LU5 powered Camaro Z28 and Trans Am. Motor Trend when it test drove the 1983 SS obtained a 0-60 mph time of 7.97 seconds and quarter mile (1/4) mile of 16.08 seconds at 85.1 mph and it commented that "it’s quicker and faster than either of the corporation’s F-cars, at least until they get L69 V-8 engines of their own". Indeed that was the case, the 1983 Camaro Z28 and 1983 Trans Am a few months later both received the L69 option rated at 190 horsepower and 240 lb-ft of torque. A Borg Wagner T5 5-speed manual was mandatory along with a performance oriented 3.73 rear axle ratio on the L69 powered 1983 Z28 and Trans Am. Car and Driver (June 1983) test drove a 1983 Camaro Z28 L69 and obtained a 0-60 mph time of 6.7 seconds and a 1/4 mile of 15.0 seconds at 93 mph. Motor Trend (June 1983) also test drove a 1983 Camaro Z28 equipped with the L69 and the result was a 0-60 mph time of 7.41 seconds and a 1/4 mile of 15.55 seconds at 90.5 mph. These times were a little slower than Car and Driver’s, however it was still considerably faster than the 175 horsepower LU5 1983 Trans Am also tested by Motor Trend (June 1983) which only managed 0-60 mph in 8.5 seconds and the 1/4 mile in 16.44 seconds at 83.6 mph. This proved the L69 was a big performance jump from the LU5.
By 1984, the L69 returned again as the Monte Carlo SS’s only engine, however it was now rated at 180 horsepower and 240 lb-ft of torque which was still 10 horsepower less than its true rating. The Monte Carlo SS for 1984 continued to use the outdated 3-speed automatic – a new mandatory 4-speed automatic transmission with overdrive would officially replace the 3-speed automatic for 1985 (there are rumors a handful of late in the model year 1984 SSs left the factory with 4-speed automatic transmissions). The Monte Carlo SS would continue through the 1988 model year with only the very slight updates, it would continue during this time to use the L69 as its only motor. Unfortunately an automatic transmission would remain the only transmission available on the SS. Chevrolet could have very easily offered the Z28’s 5-speed manual transmission in the SS, but chose not to do so – it probably didn’t want the SS to take away Z28 sales. Though the 1984 SS and 1984 Z28 used different exhaust systems both were similar in design – both were a free-flow dual outlet exhaust system which used a single catalytic converter and dual resonators. So there should have been no reason, besides Chevrolet having an ulterior motive, that the SS’s L69 was rated 10 horsepower less. The 1984 SS would retain the 1983 SS’s 3.42 rear axle ratio (the L69 equipped Z28 and Trans Am both had a 3.73 rear axle ratio). Unfortunately the SS would not get 3.73 rear gears until the 1985 model year. Popular Hot Rodding magazine (July 1984) obtained a 0-60 mile time of 7.9 seconds and a 1/4 mile time of 15.41 at 91.98 mph with a 1984 SS.
The L69 would not last as long in the Z28 and Trans Am, it would only remain until the end of the 1986 model year. Chevrolet introduced a new top performance Camaro in 1985 called the Iroc-Z, it was available with the L69 in 1985 and 1986. 1984 was the only year that the L69 was available with both the 4-speed automatic and a 5-speed manual transmission in the Camaro Z28 and Trans Am. For 1985, a new 215 horsepower 5.0 liter Tuned Port Injection (TPI) V8 was added to the Z28 and Trans Am option list. Since the 5.0 TPI V8 was only available with a 4-speed automatic for 1985-1986, the L69 for 1985-1986 served as the high-performance manual transmission motor for the Z28, Iroc-Z, and Trans Am (the L69 could not be ordered with the automatic transmission in the Z28, Iroc-Z, and Trans Am for 1985-1986). For 1986 the TPI 5.0 was detuned to 190 horsepower which was the same horsepower rating of the 1986 L69.
The L69 was different than the muscle car engines of the golden muscle car era, in that it was produced not solely for performance but also to meet the EPA’s Corporate Average Fuel Economy (CAFE) and emissions standards. The L69 was not only one of the hottest performance engines of the 1980s, when equipped with a 4-speed automatic or a 5-speed manual transmission it had an EPA highway figure of 26/27 mpg. Of course back then this type of mpg was generally obtainable only when cruising on the highway at a steady 55 to 60 mph. Owning a L69 equipped GM performance car meant you could have a muscle car that didn’t stop at every gas station it passed.
Even though all the L69s produced were identical in terms of specs (except for the SS’s lower advertised horsepower), there was one area where the L69s found in the Camaro Z28/Iroc-Z, Trans Am, and Monte Carlo SS differed. This area was the air cleaner assembly. The Monte Carlo SS used a large pedestrian round black air cleaner assembly with a single snorkel (snorkel was on the passenger side). The 1983-1984 L69 Trans Am used a smaller round black air cleaner assembly with a single snorkel (snorkel was on driver side) – the 1983-1984 L69 Trans Am’s air cleaner assembly had a large hole on the top lid to suck air from the functional hood scoop (it had a solenoid controlled flap in the hood scoop which opened up to allow air to pass to the air cleaner assembly as full throttle was approached). However it was the L69 equipped Camaro Z28 and Iroc-Z which had the most impressive looking air cleaner assembly setup – it was a small round black unit with two free-flow snorkels that received air from two large air ducts below the hood and above the radiator. The best part was the red "5.0 Liter H.O." decal on the top of the round air cleaner lid. The 1985-1986 L69 equipped Trans Am used the Z28’s dual snorkel air filter assembly since the functional hood scoop had been discontinued.
The L69 was a bright spot in GM’s performance history. Where its predecessor the LU5 merely kept performance alive, the L69 put GM’s performance cars back in 15 second range 1/4 mile territory. Unfortunately the L69 with its electronically controlled 4-bbl carburetor was not in GM’s future plans. The times were changing and port type fuel injection was the way of future due to its more precise fuel metering capabilities allowing it to more easily meet future CAFE and emissions regulations. When the 1988 Monte Carlo SS ended production, the L69 went into permanent retirement but its performance legacy still continues to this day. And for those who are tired of the current high prices of the 1960s and 1970s muscle cars, a L69 powered 1980s GM muscle car is the smart choice. There are still a good number of nice conditioned L69 powered cars around, most of these are currently very reasonably priced at well under $10,000. And there is a great future potential for these L69 powered cars increasing in price in the not too distant future. When it comes to owning a fast 1980s muscle car, a L69 powered muscle car is one of the finest choices that you can make. Popular 1980s nostalgia like parachute pants, cassette tapes, Pac-Man, boom boxes, and Sony Walkmans may all be long gone and forgotten however the L69’s legend still lives. It was the 1980s computer controlled version of the old muscle car V8 – a high-output 4-bbl V8 that was a genuine 1980s legend.
Written contents in this article – © 2012 Pete Dunton – All Rights Reserved