If the 60's were then pinnacle of the small block Chevy's development at the time,the 1970's would test the engines ability to endure politics both intra-office and government. Emissions were to become a major performance inhibitor. During the 60's the Motor Vehicle Pollution Control Act and the Clean Air Act were passed and they started to affect how manufacturers had to build vehicles. In 66 Vehicles were built specifically for California and then the rest of us. The 1970 model year would be the last of the high compression high performance small block. By 71,the compression ratios had to be dropped from 11:1 to 9:1 for the famed LT-1 and to an average of 8.5:1 for the standard small block. The 71 LT-1 was rated at 330 Horsepower for the Camaro and 350 Horsepower for the Corvette. One of the benefits of lowering compession ratios is that it emilinated cylinder wall and cylinder bulk head cracking. 1972 comes along and the big three all adopted the S.A.E. net horsepower rating formula. This lowered horsepower numbers by itself because manufacturers had to advertise the engines net horsepower numbers instead of the gross. Chevrolet and the rest of the manufactures felt that the decline in the performance market was a direct result of the decline in availability of performence engines from the factory. Everyone was weathering the storm of emissions coming into play in 1972 when the E.P.A. were leaking out that they were going to enact fuel economy standards. An interesting thing to note at this time, while street car performance interest was falling,the interest at the tracks around the country was on the rise. Sanctioned racing became very popular in the 70's. It was during this time that Chevrolet increased their popularity with racers even more than in the 60's. There was a lot of guys working at Chevrolet that were racers,it's thanks to them that they ket a lot of the key performance engine parts were still manufactured. These parts were readily available right from the dealership parts counters.
The Small Block 400.
Believe it or not the small block 400 was actually being researched and developed prior to 1968. Things like increasing the main journal diameter to 2.65 in and cutting down the bolt boss height on the connecting rods were a requirment to make the engine work. This engine was also the first small block made available with 4 bolt mains right from the start of it's production. This is partly because of the higher thrust load on the bottom end berings,the high rod angularity, and to provide more strenght limiting the amount of deflection in the crankcase. At first the thought of building the small block 400 was thought to be a stretch considering cylinder wall thickness and thus the engineers at Chevy blended the bores or what was dubbed "siammeseing" with is the term most of us hot rodders use now. These engines were also only avaliable with an automotic transmission to back them up to limit the shift speed of the tranny thus controlling the revs of the engine. These engines came out with 330 Horsepower with the RPO number LS3 and 265 Horsepower LF6 in 1970. What was really attractive about the small block 400 was the boatloads of torque. Little did anyone know at the time but,racing enthusiasts and hot rodders alike would have a heyday with the crank and rods from this engine in the future that would lead to the creation of the 383 small block Chevy. The bore of this engine was 4.125 in and the troke was 3.75 in. The engine would be in production until 1977.
The LT1 in 1970 for intended to take over the perfomance title for the 327. For the 70 model year this engine was built with the best parts available. Forged connecting rod,steel forged crank,forged aluminum TRW pistons with a mechanical 458 lift "LT1" Camshaft. The cylinder heads where the 2.02/1.60 closed chamber 64 cc heads machined for screw in studs and guide plates. A high raise Aluminum intake and a 780 Holley topped it off. And if you were lucky you got it with the "Winters" snowflake embossed on the intake. Chevy considered this particular small block to be the best they ever built to that date.
In 1975 they introduced the 265 and it was basically a boat anchor. And everyone from Chevrolet agreed.
The 305
Introduced in 1976, this displacement came from using the 3.48 inch stroke and a 3.74 inch bore. Allowing for a 1.84 sized intake valve. This engine was to take over as the base Chevy small block to suit the EPA standards for fuel economy and emissions. Believe it or not the 305 was the result of a lot of design and tested. Bore/stroke ratio is very important when it comes to and engine being either over square or under square. An over square engine requires engine spark to be retarded to the point where it kills the efficiency of the engine.That increases the exhuast gas temperature,burning unspend gases in the exhuast,good for the air,bed for fuel economy and power. The 305 was a more square engine thus meeting the emissions requirments and get decent fuel economy. However the 305 was only intended to be a 2 barrel carburetor engine and was sold as such until 1979 when the engineers at Chevrolet had tuned to configuration well enough to handle the spark advance required to make the engine efficient. Hoeever,it would be a few years yet before the 305 would shake the reputation of a slug and become a potential performance engine.
Now the lessions lerned from development of the 262 and 305 lead to the development of the 267. The only real noteworthy thing about the 267 was the square bore/stroke ratio. This engine was sold in the Monte Carlo and Malibu in California and a few other states. The engine turned out to be one of the most fuel efficient and cleanest burning motors available to date however Chevrolets research and development of the V-6 engines would negate such a small displacment small block V-8.
Overall,there were a lot of people fully believing that the V-8 was going the way of the dinosuar,there were groups of people thinking that we were going to run out of oil and that the North American love affair with the car was going to come to an end. They couldn't have been more wrong.
The Small Block 400.
Believe it or not the small block 400 was actually being researched and developed prior to 1968. Things like increasing the main journal diameter to 2.65 in and cutting down the bolt boss height on the connecting rods were a requirment to make the engine work. This engine was also the first small block made available with 4 bolt mains right from the start of it's production. This is partly because of the higher thrust load on the bottom end berings,the high rod angularity, and to provide more strenght limiting the amount of deflection in the crankcase. At first the thought of building the small block 400 was thought to be a stretch considering cylinder wall thickness and thus the engineers at Chevy blended the bores or what was dubbed "siammeseing" with is the term most of us hot rodders use now. These engines were also only avaliable with an automotic transmission to back them up to limit the shift speed of the tranny thus controlling the revs of the engine. These engines came out with 330 Horsepower with the RPO number LS3 and 265 Horsepower LF6 in 1970. What was really attractive about the small block 400 was the boatloads of torque. Little did anyone know at the time but,racing enthusiasts and hot rodders alike would have a heyday with the crank and rods from this engine in the future that would lead to the creation of the 383 small block Chevy. The bore of this engine was 4.125 in and the troke was 3.75 in. The engine would be in production until 1977.
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| Cross section of the small block 400 |
In 1975 they introduced the 265 and it was basically a boat anchor. And everyone from Chevrolet agreed.
The 305
Introduced in 1976, this displacement came from using the 3.48 inch stroke and a 3.74 inch bore. Allowing for a 1.84 sized intake valve. This engine was to take over as the base Chevy small block to suit the EPA standards for fuel economy and emissions. Believe it or not the 305 was the result of a lot of design and tested. Bore/stroke ratio is very important when it comes to and engine being either over square or under square. An over square engine requires engine spark to be retarded to the point where it kills the efficiency of the engine.That increases the exhuast gas temperature,burning unspend gases in the exhuast,good for the air,bed for fuel economy and power. The 305 was a more square engine thus meeting the emissions requirments and get decent fuel economy. However the 305 was only intended to be a 2 barrel carburetor engine and was sold as such until 1979 when the engineers at Chevrolet had tuned to configuration well enough to handle the spark advance required to make the engine efficient. Hoeever,it would be a few years yet before the 305 would shake the reputation of a slug and become a potential performance engine.
Now the lessions lerned from development of the 262 and 305 lead to the development of the 267. The only real noteworthy thing about the 267 was the square bore/stroke ratio. This engine was sold in the Monte Carlo and Malibu in California and a few other states. The engine turned out to be one of the most fuel efficient and cleanest burning motors available to date however Chevrolets research and development of the V-6 engines would negate such a small displacment small block V-8.
Overall,there were a lot of people fully believing that the V-8 was going the way of the dinosuar,there were groups of people thinking that we were going to run out of oil and that the North American love affair with the car was going to come to an end. They couldn't have been more wrong.
