“Big-Block”
My February 2007 issue of Classic Car Magazine has a technical treatise of Chevrolet’s storied “Big-Block” motor.
Automobile manufacturers were fielding bigger and bigger motors in NASCAR racing, and to satisfy the American thirst for performance — prompted by cheap gasoline and an underused highway system.
Ford was marketing a Police-Interceptor 390 cubic-inch V8, and eventually brought out a 406-cube version of the same motor.
Chevrolet was falling farther and farther behind. They had a 348 cubic-inch truck-motor, which was introduced in 1958 cars, and it could be tuned for performance. (I got a tech-sheet from Chevrolet that rated a triple-carb, solid-lifter 348 at 335 horsepower in 1959.)
But at 409 cubes the 348-block was stretching it. Blocks had to be hand-picked for the 409 displacement.
Cylinder-walls we so thin they were subject to porosity. For a larger displacement Chevrolet had to address the porosity issue.
A new engine would also allow taking advantage of ball-stud rockers.
Previously all valves in an overhead-valve engine worked off a common rocker-shaft, so all the valves had to be lined up in a row.
The infamous Chevy Small-Block introduced ball-stud rockers (as did Pontiac — it was their idea), but still all the valves were lined in a row.
The rockers in a ball-stud rocker engine were individually pivoted on ball-top studs, so that theoretically the valves could be canted this-way-and-that to enhance breathing.
This was the main advantage of the Big-Block motor; not just that it was a bigger engine, but the valves were individually canted in the cylinder-head thanks to ball-stud rockers.
The motor was almost a Hemi, although Chrysler’s Hemi used shafts for the valve-rockers; with longer rockers to reach the exhausts.
The Hemi’s high-end breathing was fantastic, but so was the Chevy Big-Block.
Chevy first gave the motor to Junior Johnson for the 1964 Daytona 500. It’s canted-valve arrangement earned it the nickname “porcupine-head.”
It was so strong it was outlawed; although why I can’t remember — I think because only Junior had it.
The infamous porcupine motor may have only been experimental, but those canted-valves made their way into the Mark IV Turbojet 396, the first Big-Block in 1965.
The Big-Block went on to ever-larger displacements: 427 (1966) and then 454 (1970). Now you can get Big-Block crate-motors up to 8+ liters — that’s 488 cubes (I think I’ve seen them at 512 cubes).
The Big-Block was very heavy, but Chevrolet got around that by introducing aluminum versions of it — the motor that dominated Can-Am racing before Porsche blew it into the weeds with turbocharging.
The Big-Block, as a big engine, also has a prodigious appetite for gasoline. It’s not something you buy groceries with, or take the kids to school or piano-lessons.
My brother in Boston has a 1971 Chevelle with a Big-Block 454, and the premium gasoline he got for it cost $6.99 per gallon. Fill your tank for over 100 smackaroos.
Fine, except it was jumping all over. Rumpeta-rumpeta-rumpeta-rumpeta! Too much motor in a blowsy old antique. Sure, take Granny to church in that.
 |
| Big-Block crate-motor |
Ford was marketing a Police-Interceptor 390 cubic-inch V8, and eventually brought out a 406-cube version of the same motor.
Chevrolet was falling farther and farther behind. They had a 348 cubic-inch truck-motor, which was introduced in 1958 cars, and it could be tuned for performance. (I got a tech-sheet from Chevrolet that rated a triple-carb, solid-lifter 348 at 335 horsepower in 1959.)
But at 409 cubes the 348-block was stretching it. Blocks had to be hand-picked for the 409 displacement.
Cylinder-walls we so thin they were subject to porosity. For a larger displacement Chevrolet had to address the porosity issue.
A new engine would also allow taking advantage of ball-stud rockers.
Previously all valves in an overhead-valve engine worked off a common rocker-shaft, so all the valves had to be lined up in a row.
The infamous Chevy Small-Block introduced ball-stud rockers (as did Pontiac — it was their idea), but still all the valves were lined in a row.
The rockers in a ball-stud rocker engine were individually pivoted on ball-top studs, so that theoretically the valves could be canted this-way-and-that to enhance breathing.
This was the main advantage of the Big-Block motor; not just that it was a bigger engine, but the valves were individually canted in the cylinder-head thanks to ball-stud rockers.
The motor was almost a Hemi, although Chrysler’s Hemi used shafts for the valve-rockers; with longer rockers to reach the exhausts.
The Hemi’s high-end breathing was fantastic, but so was the Chevy Big-Block.
Chevy first gave the motor to Junior Johnson for the 1964 Daytona 500. It’s canted-valve arrangement earned it the nickname “porcupine-head.”
It was so strong it was outlawed; although why I can’t remember — I think because only Junior had it.
The infamous porcupine motor may have only been experimental, but those canted-valves made their way into the Mark IV Turbojet 396, the first Big-Block in 1965.
The Big-Block went on to ever-larger displacements: 427 (1966) and then 454 (1970). Now you can get Big-Block crate-motors up to 8+ liters — that’s 488 cubes (I think I’ve seen them at 512 cubes).
The Big-Block was very heavy, but Chevrolet got around that by introducing aluminum versions of it — the motor that dominated Can-Am racing before Porsche blew it into the weeds with turbocharging.
The Big-Block, as a big engine, also has a prodigious appetite for gasoline. It’s not something you buy groceries with, or take the kids to school or piano-lessons.
My brother in Boston has a 1971 Chevelle with a Big-Block 454, and the premium gasoline he got for it cost $6.99 per gallon. Fill your tank for over 100 smackaroos.
Fine, except it was jumping all over. Rumpeta-rumpeta-rumpeta-rumpeta! Too much motor in a blowsy old antique. Sure, take Granny to church in that.
posted by BobbaLew at 10:40 AM
0 Comments:
Post a Comment
<< Home