JEGS Tech Specialist

Pete Mitchell

The large cubic inch size of the big block Chevy engine made it a powerful option in both Chevy cars and trucks for over 40 years and is still popular today. From restored bone-stock vehicles to all-out drag vehicles, it serves many purposes. Are you looking for BBC torque specs and other technical information? Below are answers to common questions about the BBC torque specs and more. 

How To Identify A Big Block Chevy Engine

In order to identify a big block Chevy, locate the casting number on the rear ledge at the back of the block on top where the transmission bellhousing attaches. Usually, the casting numbers are on the driver side, but it may be on the passenger side as well. The number should start with a 1,2, 3, or 4 and will not contain any letters. You can then look up the casting number on the below chart: 

0-326711 - Located to right of timing cover and rear ledge, 427, 1968-1969, 4-bolt main, aluminum, CanAm, 4.44" bore, steel cylinder liners

340220 - 427 tall deck, 1968-1985, 4-bolt main

345014 - 454, 1970 - 1986

346236 - 454, 1975 - 1976, 2-bolt main

359070 - 454, 1970 - 1990

361959 - 454, 1973 - 1990, 2 or 4-bolt main

364776 - 427 tall deck, 1968 - 1985, 4-bolt main

364779 - 366 tall deck,1968 - 1990, 4-bolt main

399204 - 509, 1970 - 1971, 4-bolt main, aluminum, CanAm, 4.5" bore, steel cylinder liners

399293 - 366 tall deck, 1977 - 1978, 4-bolt main

473478 - 427 tall deck, 1977 - 1990, 4-bolt main

495102 - 509, 1971 - 1972, 4-bolt main, aluminum, CanAm, 4.5" bore, no liners

3782870 - 427 tall deck, 1968 - 1976, 4-bolt main

3824553 - 366 tall deck, 1966 - 1967, 4-bolt main

3855961 - 396, 1965 - 1966, 2 or 4-bolt main

3855961 - 427, 1966, 2-bolt main

3855962 - 396, 1965 - 1966, 4-bolt main

3855977 - 366 tall deck, 1966 - 1973, 4-bolt main

3869942 - 427, 1966 - 1967, 2 or 4-bolt main

3902406 - 396, 1967, 2 or 4-bolt main

3904351 - 427, 1967, 2 or 4-bolt main

3904354 - 366 tall deck, 1966 - 1976, 4-bolt main

3916319 - 366 tall deck, 1968, 4-bolt main

3916321 - 427, 1968, 2 or 4-bolt main

3916323 - 396, 1968, 2 or 4-bolt main

3925521 - 427 tall deck, 1968 - 1985, 4-bolt main

3935439 - 427, 1968 - 1969, 2 or 4-bolt main

3935440 - 396, 1968 - 1969, 2 or 4-bolt main

3937724 - 366 tall deck, 1968 - 1985, 4-bolt main

3937726 - 427 tall deck, 1968 - 1984, 4-bolt main

3946052 - 427, 1969, 4-bolt main, aluminum, ZL-1, Mark IV

3946053 - 427, 1997 - later, 4-bolt main, aluminum, ZL-1, Mark IV - 2nd version

3955270 - 427, 1969, 2 or 4-bolt main

3955272 - 396, 1969, 2 or 4-bolt main

3955274 - 366 tall deck, 1968 - 1985, 4-bolt main

3955276 - 427 tall deck, 1968 - 1973, 4-bolt main

3963512 - 427, 1969, 2 or 4-bolt main

3963512 - 454, 1970 - 1976, 2 or 4-bolt main

3969852 - 366 tall deck, 1968 - 1984, 4-bolt main

3969854 - 396, 1969, 2 or 4-bolt main

3969854 - 402, 1970 - 1972, 2 or 4-bolt main

3969858 - 427 tall deck, 1968 - 1984, 4-bolt main

3999289 - 454, 1971 - 1979, 2 or 4-bolt main

3999290 - 396, 1968 - 1969, 2 or 4-bolt main, truck block

3999290 - 402, 1970 - 1972, 2 or 4-bolt main, truck block

3999290 - 402, 1972, 2 or 4-bolt main, car block

3999293 - 366 tall deck, 1968 - 1990, 4-bolt main

3999294 - 427 tall deck, 1968 - 1984, 4-bolt main

10051107 - 454, 4-bolt main, "Bowtie", MK IV, 9.8" deck, 4.25" semi-finished / siamesed  bores, 4.50" max bore

10069282 - 366 tall deck, 1990 - 1991, 4-bolt main, Mark IV

10069284 - 427 tall deck, 4-bolt main, Mark IV, truck block

10069286 - 454, 1990 - 1991, 4-bolt main, Mark IV

10114182 - 454, 1991 - later, 4-bolt main, Gen V

10114183 - 366 tall deck, 1991 - later, 4-bolt main, Gen V

10114184 - 427 tall deck, 1991 - later, 4-bolt main, Gen V

10134366 - 454 tall deck, 4-bolt main, "Bowtie", Gen V

10185050 - 454, 4-bolt main, "Bowtie", Gen V

10237297 - 454, 1996 - later, 4-bolt main, "Vortec 7400", "L-29", Gen VI

10237299 - 427 tall deck, 1996 - later, 4-bolt main, Gen VI, 7.0 liter, truck block

10237300 - 502, 1996 - later, 4-bolt main, Gen VI, 4.466" bore

12550312 - 427 tall deck, 1996 - later, 4-bolt main, Gen VI, 4.250" bore, with fuel pump and clutch linkage pivot bosses

12550313 - 454, 1991 - later, 4-bolt main, Gen V crate engine, Gen VI 4.25" bare block, with fuel pump boss

12556110 - 496, 2001 - later, 4-bolt main, Gen VII, 8.1 liter, "Vortec 8100", truck block

12561357 - 454, 1996 - later, 4-bolt main, Gen VI

12561358 - 502, 4-bolt main, Gen VI

14015443 - 454, 1987 - 1990, 2 or 4-bolt main, Mark IV, truck or motorhome block

14015445 - 454, 1978 - 1990, 2 or 4 bolt main

14044807 - 454 tall deck, 4-bolt main, "Bowtie", MK IV, "CNC Prep", 4.25" or 4.495" bore

14096859 - 502, 4-bolt main, Gen V, "HO"

24502504 - 454, 4-bolt main, "Bowtie", Gen V, "Race Prep"

24502506 - 454 tall deck, 4-bolt main, "Bowtie", Gen V, "Race Prep"

24502572 - 4-bolt main, 4.5" bore, "Olds DRCE 2", 9.5" deck height

25534402 - 4-bolt main, 4.590" bore, "Olds DRCE 3", 9.25" deck height

The casting number will confirm BBC engine specs including the size, year (or year range) of the block, and whether it is 2-bolt or 4-bolt main. Additional info may be available as well. If you want to determine the engine size without the casting number, you can measure the bore and stroke of the engine. A match can then be researched online to the corresponding engine. The stroke is measured as the distance between top and bottom dead center of the centerline of a connecting rod. Careful measurement and the help of specialty tools like a dial caliper is required for accurate measurement. The bore can be measured with a bore gauge in the block cylinder or "hole" to calculate the diameter. Note that bores can be larger due to previous engine machine work such as boring out a cylinder during a rebuild. The rear main seal type will also help indicate the year range of the block. 2-piece rear main seals were used through the 1990 year. 1991 and later blocks used a 1-piece rear main seal.     

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What Is The Best Big Block Chevy Engine?

The answer to this question depends on the application and the BBC engine specs you need. Regarding parts availability, the 454 engine has the most availability of parts in comparison to the other engine sizes. This is due to the number of blocks available for the 7.4 liter versus a 396, 402, 427, or other blocks. The Mark IV (made from 1965-1990) block is the most popular, again due to the number of available blocks and aftermarket parts. This generation includes the 396, 402, 427, and 454 engines. The Gen V and Gen VI blocks are growing in popularity. However, there are currently not as many aftermarket options for them in comparison to the Mark IV block. JEGS offers big block Chevy engines among our selection of Crate engines to meet your needs. 

How To Increase Torque In A Stock Gen 4 BBC:

There are many different ways to increase the torque in an otherwise stock Mark IV engine. The first is a camshaft swap.  Installing a cam designed to improve torque and lower the rpm power band will boost low-end power. Upgrading the crankshaft to a larger stroke (creating a "stroker" motor) will also increase power in the lower-rpm range. Additional components that can help create additional torque  include smaller cylinder heads (smaller runners and lower flow rates), a smaller carburetor, as well as a larger engine block bore. 

Big Block Chevy Firing Order

Big Block Chevy Torque Specs

Below are the torque specs big block Chevy engines require for proper sealing and operation. The big block Chevy torque specs listed may not be correct for your application. We strongly recommend you confirm torque specs for the big block Chevy you are working on with an engine shop or service manual for your specific year and model engine. In addition, the proper way to torque bolts is in three equal increments. In addition, if you are not using factory bolts, you must use the BBC torque specs the manufacturer provides, such as ARP bolts. 

-Main Caps: 396-427 CID, 2 bolt mains, use engine oil for lubricant, torque to 95 ft-lbs.

-Main Caps: 396-454 CID, 4-bolt mains (inner and outer bolts), use engine oil for lubricant, torque to

110 ft-lbs.

-Connecting Rod Bolts (Factory, Not Aftermarket): 3/8", use engine oil for lubricant, torque to 50 ft-lbs., 7/16", use engine oil for lubricant, torque to 70 ft-lbs.

-Cylinder Heads: use engine oil for lubricant in the blind holes, sealer for water jacket holes, torque to 75 ft-lbs. for the long bolts, 65 ft-lbs. for the short bolts

-Rocker Arm Studs (screw-in): use engine oil for lubricant, torque to 50 ft-lbs.

-Oil Pump: use engine oil for lubricant, torque to 65 ft-lbs.

-Oil Pan: use engine oil for lubricant, torque to 12 ft-lbs.

-Cam Sprocket (upper gear): use thread locker, torque to 20 ft-lbs.

-Timing Cover: use engine oil for lubricant, torque to 6 ft-lbs.

-Intake Manifold (with cast iron heads), use non-hardening sealer, torque to 25 ft-lbs.

-Valve Covers: use engine oil for lubricant, torque to 3 ft-lbs.

-Exhaust Manifolds: use anti-Seize Lubricant, torque to 25 ft-lbs.

-Spark Plugs: do not use lubricant or Sealant, torque to 20 ft-lbs.

-Flexplate (Automatic) and Flywheel (Clutch): use thread locker, torque to 60 ft-lbs.

-Clutch Pressure Plate: use thread locker, torque to 35 ft-lbs.

-Harmonic Balancer Damper Center bolt: use engine oil for lubricant, torque to 85 ft-lbs.

-Bellhousing (transmission to block), use engine oil for lubricant, torque to 25 ft-lbs.

Big Block Chevy Torque Specs / Sequence For Cylinder Heads 

Below are the BBC head torque specs along with the torque sequence for Mark IV blocks:

Big block Chevy cylinder head torque specifications:

Note: use engine oil for lubricant in the blind holes, sealer for water jacket holes. Torque bolts in 3 incremental stages using the torque sequence in the below diagram

Long Bolts: torque to 75 ft-lbs. (stage 1 - 25 ft-lbs, stage 2 - 50 ft-lbs, stage 3 - 75 ft-lbs)

Short Bolts: torque to  65 ft-lbs. (stage 1 - 22 ft-lbs, stage 2 - 44 ft-lbs, stage 3 - 65 ft-lbs)

Get The Right BBC Engine Specs With JEGS

Are you trying to nail down the right torque specs for a big block Chevy engine? JEGS can help. We have a great selection of engines and parts in stock, such as the Blueprint Crate Engines Big Block Chevy (496ci 575HP / 600TQ) or ATK HP Crate Engines Big Block Chevy (489ci / 565HP / 595TQ). Plus, you can always reach out to JEGS with any questions you have. We'll help you find the big block Chevy engine parts that you require for your specific application.