The History of the Chevrolet Small Block V8


1953, Chevrolet introduces the Corvette with the 235 cid "Stovebolt 6" cylinder reworked to turn out 150 HP up from 115 HP. The renamed "Blue Flame Six" does not overly impress performance enthusiasts. Rumor is that Ford will introduce an overhead valve V8 in 1954 and a two seater in 1955 to compete with the Corvette. 1954, Ford introduces their overhead valve V8. Sales of the Corvette are languishing and market share is being lost to Ford. To keep up with Ford and try to save the Corvette from extinction Chevy rushes a V8 into development. Oldsmobile and Cadillac had introduced modern V8ís in 1949 and Buick followed in 1953. Only Chevrolet and Pontiac were holding back and Pontiac had been working on a V8 since the end of the war.

Under the direction of Ed Cole, the Chevy 265 cid V8 was rushed into production and was introduced in 1955 along with Pontiacís 287 cid entry into the market. The new engine had some initial teething problems but these were quickly resolved and the Chevy small block evolved into the most successful V8 engine of all time with over 16.5 million being produced in ten different displacements over the next forty years. It is still with us today as the 5.7 liter (350 cid) V8. It saved the Corvette from extinction and restored Chevy to its former dominance over Ford. Despite numerous design improvements over the years the engineís basic geometry and key dimensions have been maintained unchanged. This continuity has contributed to the interchangeability of parts and tremendous popularity of the small block amongst performance and other enthusiasts. The availability of original and aftermarket parts for the small block Chevy V8 is not equaled by any other engine.

The 265 in the 1955 Corvette was rated at 195 HP, a substantial improvement over the six cylinder. For 1956 maximum HP for the 265 was raised to 225 HP. In 1957 the 265 was bored out to 3.875" resulting in the venerable 283 cid engine. Horsepower available for the Corvette was raised to 283 HP with fuel injection. In 1962 the 283 was bored and stroked to produce the famous 327 cid engine. The 327 was available in the "fuely" Corvette with up to 360 HP. A stroked version of the 327 was introduced in 1967 giving 350 cid.

In 1967 the 302 cid V-8, made by installing a 283 crank in a 327 block (4.00 x 3.00 inch bore and stroke), was introduced for SCCA Trans Am competition. The 1967, 302, Z-28 had 2 bolt mains; later 302ís had 4 bolt mains. The crank was forged steel. The Z-28, 302 cid engine used Corvette L-79 big port heads, with 11:1 compression ratio, 2.0 inch intake valves and 1.6 inch exhaust valves. Solid lifters and 1.50:1 rockers provided 0.485 inch valve lift. Optional cams could be fitted. Standard intake was an aluminum tuned-runner manifold with 4 barrel, 780-800 cfm Holley. The engine was officially rated at 290 HP but produced closer to 360 HP. In 1968 the 327 was given a beefed up crankshaft with 2.45" mains and 2.10" crank journals. The same year the 307 was introduced which basically was a 283 block with a small main bearing 327 crankshaft 3.875" bore x 3.25" stroke. For 1970 the largest displacement small block of 400 cid was introduced with 4 bolt mains; in 1973 the 400 was reduced to 2 bolt mains. Because of the 400ís large bore of 4.125" and cylinder spacing of only 4.40" there is no water jacket between the cylinders at the center and the cylinders are referred to as "siamesed". Although production of the 400 was stopped in 1980 there is still great interest in the engine today due to its high displacement and low cost.

The small block V8 has a deck height (centerline of crankshaft to cylinder deck measured along the centerline of the bore) of 9.025" and a height (centerline of crankshaft to top of engine along the center of the V) of 9.805". Cylinders are spaced on 4.40" centers on each bank and the centers of cylinders on the two banks are offset to accommodate the two connecting rods on each crank journal. The small blocks have been produced in 3.671", 3.736", 3.750", 3.875", 4.000" and 4.125" bores and strokes of 3.00", 3.10", 3.25", 3.48", and 3.75". Crankshaft bearings have been produced in small 2.30", medium 2.45", and large 2.65" diameters with rod journals of 2.00" and 2.10".

The Gen.I and II smallblocks as we know them will be phased out over the next few years and replaced with the Gen.III motor. The Ď98 "LS1" motor found in Corvettes, Camaros and Pontiac Firebirds are the first of the new style smallblocks. The Gen.III will soon be found in trucks applications using a cast iron Gen.III block instead of the aluminum block found in the LS1ís.

Below is a table of the main dimensions for all production small block Chev engines from 1955 to 1998 and Generation II and later blocks.

Production Chevy Small Block V8ís

CID Years Bore Stroke Main Rod Actual Liters Main
bearing Bearing CID Bearing
265 55-56 3.750 3.00 2.30 2.00 265.1 4.34 2 bolt
283 57-67 3.875 3.00 2.30 2.00 283.0 4.64 2 bolt
327 62-67 4.000 3.25 2.30 2.00 326.7 5.35 2 bolt
302 67 4.000 3.00 2.30 2.00 301.6 4.94 2 bolt
350 67-94 4.000 3.48 2.45 2.10 349.8 5.73 2&4 bolt
302 68-69 4.000 3.00 2.45 2.10 301.6 4.94 4 bolt
327 68-69 4.000 3.25 2.45 2.10 326.7 5.35 2 bolt
307 68-73 3.875 3.25 2.45 2.10 306.6 5.02 2 bolt
400 70-72 4.125 3.75 2.65 2.10 400.9 6.57 4 bolt
400 73-80 4.125 3.75 2.65 2.10 400.9 6.57 2 bolt
262 75-76 3.671 3.10 2.45 2.10 262.5 4.30 2 bolt
305 76-94 3.736 3.48 2.45 2.10 305.2 5.00 2 bolt
267 79-81 3.500 3.48 2.45 2.10 267.9 4.39 2 bolt
All 1st generation small blocks used a 5.7Ē rod length except for the
400 cid engine which used a 5.565" rod length.
Firing order 1-8-4-3-6-5-7-2

Generation II and later
350 LT5-89 3.900 3.66 2.76 2.10 349.8 5.73
350 LT1-92 4.000 3.48 2.45 2.10 349.8 5.73
265 L99-94 3.740 3.00 2.45 2.10 263.7 4.32
350 LS1-97 3.900 3.62 2.558 2.10 346.0 5.67
293 LR4-99 3.780 3.27 293.6 4.81
364 LQ4-99 4.000 3.62 363.9 5.96
325 LM7-99 3.780 3.62 325.0 5.33

L99 is Gen. II 94 and later 4.3 liter
LT5 used from 89-95 in ZR1 Corvette
LT1 is Gen. II engine
LS1 is Gen. III engine 97 and later
LR4 99 and later 4.8 liter Vortec
LQ4 99 and later 6.0 liter Vortec
LM7 99 and later 5.3 liter Vortec



Chevy Production Big Blocks

The Chevy big block was introduced in 1965 with a 396 cid Mark IV engine developed from the 1963 Datona mystery engine. The engine was basically developed as an answer to the highly successful GTO with its 389 cid engine introduced in 1964. The 396 was first offered in the Chevelle at 375 HP, in the full size Chevy as 325 and 425 HP versions and in the Corvette with up to 425 HP. In 1966 the 396 was bored out to 4.250" producing a 427 cid engine. The 427 was offered in the 1967 Impala SS rated at 385 HP and in the Corvette it was first offered in 1966 and was uprated with 3-2 bbl carburetors to 435 HP for 1967.

In 1967 the L88 427 was also provided in approximately 20 Corvettes with an advertised HP of 430 but actually producing in excess of 550 HP. The L88 required minimum 95 octane gas to avoid possible damage to the engine and was meant to be strictly for racing. 1970 saw introduction of a stroked 427 resulting in a 454 cid engine. The 454 was offered in the 1970 Impala, Chevelle SS, El Camino SS and Monte Carlo SS in a 360 HP version and in the Chevelle and El Camino SS in a 450 HP version. The 1970 Corvette LS-6 was offered with the 390 HP 454 cid engine. 1970 also ushered in the 402 cid engine which was also known as the 396 in some Chevys and the big block 400 in others. In the 1970 Camaro SS, Chevelle SS and Nova SS the 402 cid engine with 375 HP was known as the 396 and the cars carried the 396 badge. From 1970 to 1972 the 402, 454, 465 and 495 cid engines were introduced.

The short big block V8 has a deck height (centerline of crankshaft to cylinder deck measured along the centerline of the bore) of 9.80" and a height (centerline of crankshaft to top of engine along the center of the V) of 10.75". Cylinders are spaced on 4.84" centers on each bank and the centers of cylinders on the two banks are offset to accommodate the two connecting rods on each crank journal. The big blocks have been produced in 3.935", 4.096", 4.125", 4.250", and 4.440" bores and strokes of 3.47", 3.76", and 4.00". Over the years from 1965 to 1995 the big blocks were offered in nine different displacements from 366 cid to 502 cid.

Below is a table of the main dimensions for all production big block Chev engines from 1965 to 1995.


Production Big Block V8ís

CID Years Bore Stroke Block Material Actual Liters Main
CID Bearing
396 65-69 4.096 3.76 Cast Iron 396.4 6.50 2&4 bolt
366T 66-95 3.935 3.76 Cast Iron 365.8 5.99 2&4 bolt
427 66-69 4.250 3.76 Cast Iron 426.7 6.99 2&4 bolt
427T 69-95 4.250 3.76 Cast Iron 426.7 6.99 4 bolt
427 69 4.250 3.76 Alum.w/liners 426.7 6.99 4 bolt
430 69 4.440 3.47 Alum.w/liners 429.8 7.04 4 bolt
454 70-91 4.250 4.00 Cast Iron 454.0 7.44 2&4 bolt
402 70-72 4.125 3.76 Cast Iron 402.0 6.59 2&4 bolt
465 70-71 4.440 3.76 Alum.w/liners 465.7 7.63 4 bolt
495 70-71 4.440 4.00 Alum.w/liners 495.5 8.12 4 bolt
495 72 4.440 4.00 Alum.no liners 495.5 8.12 4 bolt
502 92-94 4.466 4.00 Cast Iron 501.3 8.21 4 bolt

All big blocks have 2.75" main bearings and 2.20" rod bearings and all production big blocks used a 6.135" rod length. T is Tall (or long) block with a deck height of 10.20" and vertical height of 10.75".
Firing order 1-8-4-3-6-5-7-2


The other Chevy V8ís

How could we forget the legendary 409 cid engine first introduced in 1962. It evolved from another great engine the 348 cid V8 that ruled the road from 1958 to 1962. My 1961 Chevy had a 348 with the tri-power option putting out advertised 330 HP and with a 4.56 rear end it was unbeatable up to about 90 mph. The 348 was bored and stroked until it displaced 409 cubic inches. The 409 engine was pure muscle; full sized Chevys turned 12.55 quarter miles at 116 mph. The cam, valves, compression ratio of 10.2:1, head design and large dual exhausts all worked together to produce one of the most exciting engines in history. It was available in the Impala, but hot rodders in the know preferred their 409 in the lighter Bel Air body. The 409 was a great engine but Chevy needed something to answer the Chrysler 426 Max Wedge, the Ford 427 and the Pontiac Super Duty 421. In 1963 the 409 was stroked to 3.65" to produce 427 cid and along with liberal use of aluminum, special heads and intake manifold the Z11 engine/Impala was born. Officially rated at 430 HP, several sources suggest that actual output was significantly higher than 500 HP.

In January 1963, the GM brass passed down an edict to its divisions to stop any work going on with performance programs. Sadly, as a result, only 57 Z11ís were made. They were all T-10 four speed equipped Impala SS cars. However, the Z-11ís that made it to the racetrack cleaned up shop. The Strickler/Jenkins car won the eliminator bracket at the 1963 NHRA U.S. Nationals in Indianapolis, running a 12.10 second pass at a flying 120.16 mph.

Below is a table of the main dimensions for the "W" engines produced from 1958 to 1965.


"W" Family V8 Motors

CID Years Bore Stroke Block Material Actual Liters Main
CID Bearing
348 58-65 4.125 3.25 Cast Iron 347.5 5.69 4 bolt
409 62-65 4.312 3.50 Cast Iron 408.9 6.70 4 bolt
427 63 4.312 3.65 Aluminum 426.4 6.99 4 bolt

348 had 6.135" rod
409 had 6.000" rod
427 had 6.135" rod Z-11

ALL "W" family motors used 2.50" main bearings and 2.20" rod bearings



Non Production Chevy V8ís

Because of the interchangeability of parts in the Chevy small blocks several other displacements have been produced aftermarket for performance purposes. A 377 cid engine is produced using a 400 block bored 30 thou over and a 350 crankshaft. The 334 is a 305 block bored 0.030" over with a 400 crank and a 383 cid is a 350 block bored 0.030" over and a 400 crankshaft.


For your non- production chevy small blocks area, I have a couple of more
combos that you might wish to post, the first is straight forward, but the
second one is a bit tricky.

1) Using a 400 block .030 over and a 327 (3.25") crank, you get a 353.
Some guys like to buzz 'em at high revs.

2) Another trick is to use a 400 .030 over, take the 400's crank, and have the rod
journals re-ground off-set from the crank centerline to a new 2.00" small journal size
from the standard 2.10". The additional +.10 result is a stroke of 3.85" from
3.75" from the good 'ole 400's nodular iron crank. The catch is that you use
the smaller journal rods from production small blocks, 5.7" rods-2.00"
journal. Using trick pistons, this combo gives you a stout 417 cubic inches!
Fun stuff.