Casting numbers on the Gen I cylinder heads are cast in the heads where the rocker arms and valve springs do their work.

The GM small block was specifically designed as a compact sized engine to embrace the economical use of iron and to streamline the production process. Part of the design process that was carried through to the Gen III design in 1997 was to create lightweight rocker arms for higher rpm operation, wedge combustion chambers for a broader power band, and deliver 4.4 inch bore centers (from the center of one bore to the center of the next bore).

The first small block with a 4 inch bore came in the ’62 Corvette 327, and it really opened eyes. Featuring the famous double hump marking on the ends of the heads, the #3782461 and #3782461X heads used 1.94/1.50 inch valves. These were commonly called “Fuelie” heads because they were released with mechanical Rochester fuel injection on the stock engines. The only difference between the two casting numbers was that the #3782461 featured 160cc intake port, 62cc exhaust port and the #3782461X had the larger 172cc intake port, 64cc exhaust port.

The double hump heads continued to be a favorite with performance minded enthusiasts into the new millennium.

High performance enthusiasts separated the stock Gen I heads into closed chamber and open chamber heads. By far, the closed chamber factory heads were favored over the open chamber for making power due to the poor burn characteristics and no swirl (quench) inside the combustion chamber of the open chamber heads. 

Chevrolet Performance LS3 Cylinder Head

Chevrolet Performance LS3 Cylinder Head

Small Block Chevy LS Cylinder Heads by Casting Number 

10215339 – LS Small Block V8 1997 346, LS1, aluminum, 68cc chambers

12480005 – LS Small Block V8 2000 LS1, GTZ, aluminum, 38cc chambers, 2.125/1.625 valves, angle plugs

12556743 – LS Small Block V8 1999 325, 5.3L, aluminum, truck, van

12558806 – LS Small Block V8 1997-1998 346, LS1, aluminum, 68cc chambers

12559853 – LS Small Block V8 1999 346, LS1, aluminum, 68cc chambers

12559862 – LS Small Block V8 1999-2000 aluminum, LS, 4.8 or 5.3L

12559895 – LS Small Block V8 2000 325 (5.3L) aluminum

12561706 – LS Small Block V8 2001-2004 325 (5.3L) aluminum

12561873 – LS Small Block V8 1999-2001 364, 6.0L, LS, 71cc chambers, cast iron

12562317 – LS Small Block V8 2001-2004 364, 6.0L, LS, 71cc chambers, aluminum

12564241 – LS Small Block V8 2000 346, LS1, aluminum, 68cc chambers

12564243 – LS Small Block V8 2001 346 (5.7L LS6) or 364 (6.0L LS2), aluminum

12572035 – LS Small Block V8 2001-2004 364, 6.0L, LS, aluminum, 71cc chambers

12550592 – LS Small Block V8 1997-up 346, LS1

12559846 – LS Small Block V8 1998-up 346, LS1

12560621 – LS Small Block V8 1998-up 346, LS1

12562174 – LS Small Block V8 1998-up 346, LS1

LT1 Small Block V8 cylinder head, casting number 10125320.

10106178 – LT Small Block V8 1990 350, LT5, Corvette ZR1, DOHC 32-valve, aluminum, passenger side head

10106179 – LT Small Block V8 1990 350, LT5, Corvette ZR1, DOHC 32-valve, aluminum, drivers side head

10125320 – LT Small Block V8 1994-1996 350, LT1, cast iron, Caprice 9C1 Police, Impala SS, Cadillac Fleetwood, Buick Roadmaster, reverse flow cooling

10128374 – LT Small Block V8 1992 350, LT1, 53cc chambers, angle plugs, aluminum, reverse flow cooling, 175cc intake ports, 68cc exhaust ports

10174389 – LT Small Block V8 1991-1995 350, LT5, Corvette ZR1, DOHC 32-valve, driver side, aluminum

10174390 – LT Small Block V8 1991-1995 350, LT5, Corvette ZR1, DOHC 32-valve, passenger side, aluminum

10205245 – LT Small Block V8 1993 350, LT1, aluminum, reverse flow cooling, 175cc intake ports, 68cc exhaust ports

10207643 – LT Small Block V8 1994-1996 350, LT1, aluminum, reverse flow cooling, 175cc intake ports, 68cc exhaust ports

10208890 – LT Small Block V8 1994-1996 265, Baby LT1, L99, cast iron, reverse flow cooling

10225121 – LT Small Block V8 1994-1995 350, LT5, Corvette ZR1, DOHC 32-valve, drivers side, aluminum

10225122 – LT Small Block V8 1995 350, LT5, Corvette ZR1, DOHC 32-valve, passenger side, aluminum

10239902 – LT Small Block V8 1996 350, LT4, aluminum, reverse flow cooling, 195cc intake ports, 54cc chamber, angle plugs

12529742 – LT Small Block V8 1995-1996 265, Baby LT1, L99, cast iron

12551561 – LT Small Block V8 1996 350, LT1, aluminum, reverse flow cooling

12554290 – LT Small Block V8 1994-1996 350, LT1, Caprice 9C1 Police, Impala SS, Cadillac Fleetwood, Buick Roadmaster, reverse flow cooling

12554291 – LT Small Block V8 1995-1996 265, Baby LT1, L99, cast iron

12555690 – LT Small Block V8 1996 350, LT4, aluminum, reverse flow cooling

14088526 – LT Small Block V8 350, LT1, aluminum

Small Block Chevy Gen I Cylinder Heads by Casting Number 

10033867 – V8 aluminum, Pontiac 23 degree head, 62cc chambers, angle plugs, 196cc intake ports

the famous double hump marking on the ends of the heads, the #3782461 and #3782461X heads used 1.94/1.50 inch valves. These were commonly called “Fuelie” heads because they were released with mechanical Rochester fuel injection on the stock engines.

The famous double hump cylinder heads, the #3782461 and #3782461X used 1.94/1.50-inch valves. These were commonly called “Fuelie” heads because they were released with mechanical Rochester fuel injection on the stock engines.

10045434 – V8 aluminum, Pontiac 15 degree head, 55cc chambers, angle plugs, raised runners

10051101 – V8 Bowtie, aluminum, 55cc chambers, angle plugs, raised runners, 196cc intake ports

10065202 – 1987-1995 350, truck

10065203 – 1987-1995 350, truck

10065204 – 1987-1995 350

10065205 – 1987-1995 305

10065206 – 1987-1995 350

10065207 – 1987-1995 305

10088113 – SBC350, Aluminum, 58cc, angle plugs, raised runners, d-port exhaust, 1.94/1.5 valves

10093328 – V8 Pontiac 15 degree head, aluminum, 224cc intake ports, 61cc chambers

10110810 – 1991 350, 65cc chambers

10120928 – 1987-1995 350

10134352 – V8 Bowtie, 45cc chambers, angle plugs, low port, 223cc intake ports, aluminum, 18 degree race head

10134363 – V8 Aluminum, 18 degree or 15 degree, Bowtie race head.

10147898 – 1995-1998 350, crate engine

10159550 – 1987-1995 350

10159551 – 1987-1995 305

10159552 – 1987-1995 350

10159553 – 1987-1995 305

10185040 – V8 Bowtie, aluminum, 45cc chambers, symmetrical ports, 263cc intake ports, splayed valves

10185040 – V8 Bowtie, aluminum, 45cc chambers, symmetrical ports, 240cc intake ports, splayed valves

10239906 – 1996 350, Vortec 5700, L31, 64cc chambers, 170cc intake ports, 1.94/1.5 valves

12367712 – 1999 Fast Burn, aluminum, 210cc intake ports, port, 2.00/1.55 valves, 62cc chambers

12367713 – 1999 ZZ430 crate engine, aluminum, 210cc intake port, 2.00/1.55 valves, 62cc chambers

12480011 – 1997 Bowtie SB2.2, aluminum

12506450 – 1987-1995 350

12509859 – 1987-1994 305

12516852 – 1987-1995 350

Casting number 25534421.

Casting number 25534421.

12552520 – 1997 305, Vortec, truck

12558059 – 1997 305, Vortec, truck, 1.84/1.5 valves

12558062 – 1998 350, L31 Vortec, truck, 64cc chambers, 1.94/1.5 valves, 170cc intake ports

14008856 – 1979-1981 267

14010201 – 1982-1985 305

14010516 – 1980-1986 350

14011034 – V8 Bowtie, cast iron, 64cc chambers, 184cc intake ports, angle plugs

14011049 – Bowtie, aluminum, 55cc chambers, angle plugs, 180cc intake ports

14011083 – 1955-1986 350, crate engine, 285hp or 300hp, 64cc chambers, 1.94/1.5 valves

14014415 – 1980-1985 267 or 305

14014416 – 1980-1986 305, 1.84/1.5 valves, 58cc chambers

14014440 – 1980 305, 1.84/1.5 valves

14019821 – 1980-1986 350

14019924 – 1979-1981 267

14019926 – 1980-1986 350

14020517 – 1980 350

14020555 – 1981 305

14020556 – 1981 350

14022056 – 1985 350

14022206 – 1980 350

14022301 – 1980-1986 305

14022601 – 1980-1986 267 or 305, 1.72/1.5 or 1.84/1.5 valves, 53cc chambers

14022801 – 1980-1986 305

14024816 – 350, 76cc chambers, 1.94/1.5 valves, crate engines

14034806 – 1978-1982 267

14034807 – 1978-1986 305

14034808 – 1980-1986 350

14034808 – 1996 350, 76cc chambers, 1.94/1.5 valves, Goodwrench crate engines

14034810 – 1980-1986 350, truck

14034811 – 1980-1986 350, truck

14039121 – 1981-1986 305, truck

14039122 – 1981-1986 305, truck

14071114 – 1980-1986 350

Casting number 19300955

Casting number 19300955

14075381 – 1980-1986 350, truck

14079261 – 1986 350

14085844 – 1980-1986 350, truck

14085963 – 1986 350

14089119 – 1986-1988 350

14094093 – 1986-1988 350

14096217 – 1955-1986 350, crate engine, 285hp or 300hp, 64cc chambers, 72 degree or 90 degree center intake manifold bolt angles

14101081 – 1987-1995 305

14101083 – 1987 350, crate engines, 285hp or 300 hp, 64cc chambers, 72 degree center manifold bolt angles

14101128 – 1986-1987 350, aluminum, 58cc chambers, angle plugs

14102187 – 1987-1991 305, 1.84/1.5 valves

14102191 – 1987 350

14102193 – 1987 305 or 350, 1.94/1.5 valves

1816887 – 1963 283, GMC HD truck

22542525 – Dart or Olds or Chevy aluminum, 14 degree or 17 degree race head

24502559 – 1996-1997 Bowtie, SB2, 1st version, mirror ports, aluminum, 196cc port, CNC version, 280cc intake ports, 38cc chambers

25500141 – Buick or Chevy aluminum, 10 degree race head, 42cc chambers, symmetrical ports, 235cc intake ports, 2.1/1.625 valves

25534351C – 2004 Bowtie, cast iron, Vortec, 175cc intake ports, 65cc exhaust ports, 2.00/1.55 valves

25534371C – 2004 Bowtie, cast iron, Vortec, 206cc intake ports, 77cc exhaust ports, 2.00/1.55 valves

330545 – 1973 350, 76cc chambers, 2.02/1.60 valves

333881 – 1974-1975 350, 76cc chambers, 2.02/1.60 valves

333882 – 1974-1980 350 or 400, 76cc chambers

33417369 – 1990 350, Goodwrench crate engine, 76cc chambers

340292 – 1970 replacement, angle plugs, 64cc chambers

354434 – 1975-1979 262 or 267 or 305, 60cc chambers

358741 – 1976-1979 305

3636839 – 1955 265

3703523 – 1955 265

3713358 – 1955-1956 265

Casting number 3795896

Casting number 3795896

3713569 – 1955-1956 265

3725306 – 1956 265

3731539 – 1957 283, 283hp, mechanical fuel injection

3731544 – 1957-1961 283

3731554 – 1957-1962 283

3731556 – 1957 283, truck

3731762 – 1956 265, Corvette

3737775 – 1962-1967 283 or 327

3740997 – 1957 283, carb or fuel injection, not 283hp

3743056 – 1958 283

3743096 – 1962-1967 327, GMC Truck

3747363 – 1957-1961 283

3747460 – 1959-1967 283 or 327, 70cc chambers

3748770 – 1958 283

3748772 – 1958-1961 283

3755537 – 1957-1962 283

3755539 – 1958-1962 283

3755549 – 1957-1962 283

3755550 – 1959 283

3755585 – 1962-1967 327, GMC Truck

376445 – 1977-1985 350, 76cc chambers, small valves

376450 - 1975-1981 262 or 267 or 305. 6 or 7 exhaust bolt holes, 60cc chambers

3767460 – 1959-1960 283

3767462 – 1962-1967 327

3767465 – 1959-1961 283

3767754 – 1959-1961 283, 60cc chambers

3767792 – 1960-1964 283

3774682 – 1960-1964 283 or 327, 70cc chambers

3774684 – 1962-1964 327, 75cc chambers

3774692 – 1958-1964 283, 60cc chambers

3782461 – 1964-1966 327, camel hump, no accessory holes, 160cc intake ports, 62cc exhaust ports, 62cc chambers

Casting number 3795896. Manufactured from 1963-1965 on 283 Cubic Inch engines. Called the “Power Pack” cylinder heads. 1.72˝ intake valves and 1.50˝ exhaust valves. 60cc Combustion Chambers.

Casting number 3795896. Manufactured from 1963-1965 on 283 Cubic Inch engines. Called the “Power Pack” cylinder heads. 1.72˝ intake valves and 1.50˝ exhaust valves. 60cc Combustion Chambers.

3782461X – 1960-1963 283 or 327, camel hump,no accessory holes,larger 172cc intake ports, 64cc exhaust ports, 62cc chambers

3795896 – 1963-1965 283, 60cc chambers

3795896 – 1962-1964 327, 60cc chambers

3798996 – 1963-1967 327

3814480 – 1960-1967 283 or 327, 70cc chambers, 1.72/1.5 valves

3814482 – 1962-1967 283 or 327 or 350, 75cc chambers

3817680 – 1963-1967 283 or 327

3817681 – 1962-1967 327

3817682 – 1961-1962 283

3836839 – 1955 265

3836842 – 1957-1967 283 or 327

3837064 – 1956-1962 265 or 283

3837065 – 1955-1956 265, truck

3848720 – 1957-1958 283

3876775 – 1960-1967 283 or 327, 75cc chambers

3884520 – 1960-1967 283, 60cc chambers, some used by Studebaker

3884520 – 1962-1967 327, 60cc chambers, some used by Studebaker

3890462 – 1966-1967 302 or 327 or 350, camel hump, no accessory holes, 64cc chambers

3901068 – 1987-up 350, crate engine, 285hp, 64cc chambers

3911032 – 1968 307 or 327, 70cc chamber

3912264 – 1958-1962 283

3912265 – 1963-1964 283

3912311 – 1965-1967 327

3912313 – 1965-1967 327

3917290 – 1967-1968 307 or 327

3917291 – 1967-1968 302 or 327 or 350, camel hump, no accessory holes, 64cc chambers

3917292 – 1968 327 or 350, camel hump, 64cc chambers

3917293 – 1967-1968 307 or 327, 75cc chambers

3927185 – 1969-1976 307 or 327 or 350, 70cc chambers

3927186 – 1969-1970 302 or 350, camel hump, 64cc chambers, has accessory holes

3927187 – 1969-1970 350, camel hump, 64cc chambers, has accessory holes

3927188 – 1969 327, 74cc chambers

3927188 – 1970 307, 74cc chambers

3931633 – 1968-1973 307

3931635 – 1968-1976 350

3931638 – 1968 327, truck

3932441 – 1969-1970 350, 76cc chambers

3932441X – 1969-1970 350 or 400, 80cc chambers

3932454 – 1969-1973 307

3932454 – 1969-1979 350, truck

3946812 – 1969 350

3946813 – 1969-1979 350, truck

Casting number 12529093

Casting number 12529093

3947040 – 1968 327, 64cc chambers, truck, no accessory holes

3947041 – 1969-1970 302 or 350, 64cc chambers

3947041X – 1969-1970 302 or 350, 64cc chambers, 165cc intake ports

3951598 – 1970 400, 76cc chambers

3964286 – SBC 350

3965742 – 1970 350, replacement, angle plugs

3970126 – 1967-1971 327 or 350

3973370 – 1969-1970 350, 64cc chambers, straight plugs or angle plugs

3973414 – 1970 350, LT1, 350hp or 370hp, camel hump, 64cc chambers

3973487 – 1971-1972 350, 1.94/1.5 or 2.02/1.6 valves, also 1971 350 or 330hp LT1, 75cc chambers

3973487X – 1971-1972 350, 1.94/1.5 or 2.02/1.6 valves, 75cc chambers

3973493 – 1971-1972 400, 76cc chambers

3986316 – 1971 350, 76cc chambers

3986336 – 1971 350, 76cc chambers

3986336X – 1971 350, 76cc chambers

3986339 – 1971 307 or 350, 74cc chambers

3986339X – 1971 307 or 350, 74cc chambers

3986388 – 1968-1976 307 or 350

3991492 – 1970 350, LT1, camel hump, accessory holes, 64cc chambers, straight plugs

3991492 – 1970 camel hump, 64cc, straight plugs or angle plugs

3998916 – 1972 350, 1972 350 LT1, screw in studs, 76cc chambers

3998920 – 1972-1973 350

3998991 – 1972-1973 307 or 350, 75cc chambers

3998993 – 1972-1973 307 or 350, 75cc chambers

3998993 – 350, Goodwrench crate engine, 75cc chambers

3998997 – 1972-1973 350 or 400, 76cc chambers

3998997 – 1978-1984 305 or 350, 76cc chambers

4079261 – 1975 350

458642 – 1975-1984 350, 350

462614 – 1977-1979 305, 60cc chambers

462624 – 1975-1986 350 or 400, 76cc chambers, 1.72/1.50, 1.94/1.50 or 2.02/1.60 valves

468642 – 1976 350 or 400

471513 – 1979 267 or 350

517513 – 1979 267 or 350