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Chevelle V8 Engine Block Casting Numbers (Group 0.033)

These block castings were used in various other models of the Chevrolet lineup such as the passenger car, Chevy II/Nova, Camaro and Corvette. Only Chevelle-specific information is listed here to conserve space. Some casting numbers are NOT listed as they may have been used in other models of the Chevrolet lineup but were NOT used in the Chevelle - such as the 1965/66/67 Chevy II blocks #3790721 and 3791362.

It's important to remember the 'to' and 'from' dates listed may vary due to production lead time and stock inventories being depleted. For example just because a particular block casting may be listed as being used for a particular year doesn't imply that the engine assembly plants discarded all currently cast blocks or newer castings/designs did not come into play if current stocks were depleted sooner than planned.

V8 Engine Block Casting Month Codes
A - January	D - April	G - July	J - October
B - February	E - May	H - August	K - November
C - March	F - June	I - September	L - December

Date codes are the letter, 1 or 2 digits for the day, and 1 digit for the year such as J 25 7 would be October 25, 1967. One exception seems to be the 1970 engine blocks being dated as month letter, 1- or 2-digit date, and a 2-letter year number (70). If anyone has a photo of a KNOWN 1970 block with a single digit year code (0), please send me a photo of it and how you know it's a 1970 block.

The block casting number on small block and big block Chevy V8 motors is located on a ledge found at the rear of the block, most often on the driver's side. This ledge is below the deck of the block and the ledge forms the mating surface between the block and the transmission bellhousing. The matrix below is for Chevelle applications only although many were used in other makes of the Chevrolet Division.

At least one 1968 block #3914678 has been found with a casting date of 2 25 8 - a single-digit number for the month instead of a letter.

Block Number	Year	Engine	Horsepower	Notes
3849852	1964	283	195, 220	Began life with the 1963 commercial truck line and used through 1966.
3782870	1964 1965	327	250, 300, 350⁽²⁾	During 1965 model year, #3858180 was released in some applications. All #3782870 blocks should have nodular bearing caps. On 300hp and above, they all have chamfered main bearings.
3834810	1964 1965 1966	283	195, 220	Used only by Tonawanda Engine assembly plant. Essentially identical to #3984852.
3849852	1965 1966	283 283	195, 220 195, 220
3855961	1966	396	325, 360	Blueprints show this to be a 2-bolt block only. Is identical to #3855977 (366 truck) except for the passenger car deck heights, cylinder wall revisions and minor casting and machining. Does not have dowel pins for locating timing chain cover. Casting date on the right lower side near the freeze plug in front of the starter. Has 'tall tower' distributor casting boss. A 4-bolt version was introduced around April of 1966 as the 3855962 block was being phased out. This block is known to have been installed in L78 applications; 325hp or 360hp applications are unsure.
3855962	1965 Z16 1966	396 396	375 360⁽¹⁾, 375	Blueprints indicate this is a 4-bolt block only. Is identical to #3855977 (366 truck) except for the passenger car deck heights, cylinder wall revisions and minor casting and machining. Block has thicker cylinder walls than #3855961. Most were cast after February 15, 1965 as that was the introduction date of the 396. Does not have dowel pins for locating timing chain cover. Casting date on the right lower side near the freeze plug in front of the starter. Has 'tall tower' distributor casting boss.
3858174	1966	327	275, 350⁽³⁾	Chevrolet shows this block being used as early as 1964 in 300+ hp applications and commercial trucks. Used interchangeably with #3858180 in some applications. This block has been found to have been used on some late 1965 model year L79 Chevelles built at Baltimore.
3858180	1965 1966	327 327	250, 300, 350⁽²⁾ 275, 350⁽³⁾	Used interchangeably with #3782870 but had significantly thinner cylinder walls and larger water jacket.
3892657	1967	327	275, 325	Also used as new 350 engine for Camaro.
3896944	1967	283	195	Tonawanda cast block was used only for the 1967 model year and was the last 283 design.
3896948	1967	283	195	Flint cast block.
3902406	1966 1967	396 396	360, 375 325⁽⁴⁾, 350⁽⁴⁾, 375	Used in very late 1966 and 1967 models only. Second design 396 block. Primary difference between this and the #3855961/962 block is the casting of the oil galleys. First design built in both 2-bolt and 4-bolt configurations. Does not have dowel pins for locating timing chain cover. Casting date on the right lower side near the freeze plug.
3903352	1967	327	275, 325	Used mid to late in 1967 model year.
3914636	1968	307	200	Used only in 1968
3914660	1968	327	250, 275	Identical to #3914638 except for minor interior casting at bottom of cylinder bores for rod clearance.
3914678	1968	327	250, 275, 325	Identical to #3914636 except for minor interior casting changes to cylinder wall and water jacket sizing.
3916323	1967 (late) ⁽⁷⁾ 1968 (early)	396	325⁽⁴⁾, 350⁽⁴⁾, 375	Used from June of 1967 to June of 1968. First block to use spin-on filter in place of canister filters used in early Mark IV engines. Block #3935440 began replacing this block around January of 1968. Casting date on the right lower side near the freeze plug in front of the starter. Has 'tall tower' distributor casting boss.
3932386	1969	350	300	Used from August 1968 until approximately January of 1969 when replaced with 3956618. Used only as 4-bolt block.
3935440	1968 (mid/late) 1969 (early)	396 396	325⁽⁴⁾, 350⁽⁴⁾, 375 325⁽⁴⁾, 350⁽⁴⁾, 375	Used for all 396 applications from mid to late 1968 and early 1969. Production stopped approximately August of 1968 although supplies would have been used in production until exhausted. Casting date on the right lower side near the freeze plug in front of the starter. Has 'tall tower' distributor casting boss.
3955272	1969	396	325⁽⁴⁾, 350⁽⁴⁾, 375	Used from approximately September of 1968 to June of 1969. Sometime between casting dates January 7 and March 17 the casting date position was moved to rear of bellhousing flange.
3956618	1969	350	250⁽⁵⁾, 255⁽⁵⁾, 300
3956632	1969	307	200	Used only in 307 applications.
3951509	1970 1974 1975	400 400 400	265⁽⁸⁾ 150, 180⁽⁸⁾ 175⁽⁸⁾	Produced in Flint for 1970/1971. Dropped for 1972/1973 and reinstated in 1974/1975.
3951511	1970	400	265⁽⁹⁾	Produced in Tonawanda.
3963512	1969 1970 1971	427 454 454	425 (COPO) 360, 450 365, 425⁽⁶⁾	Used in both 427 and 454 applications. Lower hp versions used 2-bolt main bearing caps while higher hp versions were 4-bolt main. Block had 'high tower' distributor boss and casting date located on the side of the block until redesigned on November 17, 1969 when recast with 'short tower' distributor boss and casting date moved to bellhousing area. It should be noted that much earlier 427 and 454 engine blocks have been found with casting dates as early as September 5, 1969 in a 2-bolt configuration and several in the October timeframe in a 4-bolt configuration. ⁽¹⁰⁾
3969854	1969 (late) 1970 1971 1972	396/402 * 402 402 402	325⁽⁴⁾, 350⁽⁴⁾, 375 330⁽⁴⁾, 350⁽⁴⁾, 375 300 240	Used in all 402 applications. Block has 'short tower' distributor boss and casting date is found on top of bellhousing flange near casting number.
3970010	1969 1970 1971 1972 1973 1974 1975	350 350 350 350 350 350 350	300 250⁽⁵⁾, 300 245, 270 165, 175 145, 175 145, 160 145, 155	First appeared in late April or early May of 1969 and used through 1975. Used in both 2- and 4-bolt configurations and varied from year to year. Chevrolet shows this block only used in 4-bolt versions in 1969 Chevelles.
3970014	1970	350	300	Supposedly used only by Camaros in 1970, this block is documented in a 1970 Chevelle, 350-4 w/TH350. Also used from 71-73 in Camaro (71) and Corvette (early 73) as well as Chevelles in 1973.
3970020	1970 1971 1972 1973	307 307 307 307	200 200 130 115	Used for 307 applications only.
3970024	1970 1971 1972	307 307 307	200 200 130	Used for 307 applications only. Cast at the Tonawanda Engine Plant and all #3970024 engines to date have been identified as being assembled at Tonawanda.
3999289	1972 1973 1974 1975	454 454 454 454	270 215 235 215	Also saw heavy truck usage until 1978. Although Chevelle engines were 2-bolt main blocks, there have been 4-bolt main versions of this block found.
3999290	1972	402	240	1972 Chevelle
330817	1974 1975	400 400	150, 180 175
346236	1975	454	215	Mid-year 1975.

* The 402 engines were used in Chevelles. There has been one reported 07E 22 1969 engine block with this casting number. There are reportedly documented late 1969 Camaros with the 402.

⁽¹⁾ It has been verified that this block was installed in some 1966 Chevelle 396/360 applications causing problems for Chevrolet Service when warranty replacements required a partial engine assembly or fitted block service replacement. If the 4-bolt 375hp assembly was used to replace the 4-bolt 360hp engine, cylinder heads from the 360hp engine would interfere with the domed pistons of the 375hp block replacement. Specific partial engine and fitted block assemblies were noted for replacements. Some, if not all, 360hp engines used this block even though it was not called for that application by Chevrolet.

⁽²⁾ The 327/350hp configuration was optional in 1965 but dropped for the 1966 model year until March 1966. It's been brought up that the overwhelming majority of casting #3782870 blocks are from the Flint, MI. engine plant and supplied by Saginaw foundry while the #3858180 was done in-house at Tonawanda Engine Plant Correspondence with 1965 Chevelle L79 owners indicate that of the engines reported, most are from the Flint engine facility. My thanks goes to Mr. Randolph for alerting me to this and Mr. Cummings for his input.

⁽³⁾ The 327/350hp configuration was reintroduced for the 1966 model year in March 1966. Although there are engine suffix ID codes for a 1966 327/350, Chevrolet does not report any L79 options being sold in the 1966 model year.

⁽⁴⁾ In 396-cid applications 325hp and 350hp versions were 2-bolt main bearing caps. High performance applications were 4-bolt main bearing caps.

⁽⁵⁾ In 350-cid applications 250hp and 255hp versions were 2-bolt main bearing caps. High performance applications were 4-bolt main bearing caps.

⁽⁶⁾ In 1971 454 applications, the LS6 with 4-bolt mains was only available in the Corvette.

⁽⁷⁾ At least one 3916323 block has been found with older canister type oil filters in a June 1967 Chevelle.

⁽⁸⁾Monte Carlo (1970), Chevelle/Monte Carlo (1974-1975); 1970 is 4-bolt main, 1974-1975 are 2-bolt main.

⁽⁹⁾ Monte Carlo; 4-bolt main.

⁽¹⁰⁾ This 3963512 block dated October 15, 1969 has casting date on bell housing flange and is a warranty block.

Two bolt vs. four bolt main block

Note the differences between a big block (396/454) 2-bolt main (upper photo) and 4-bolt main (lower photo) block above the oil filter location.

© ChevelleWorld
The 2-bolt main block has the 5/16" front hole that is not drilled and tapped into the oil galley, the center hole is drilled and tapped into the oil galley with a 3/8" pipe thread hole and the rear hole is 1/2" UNC coarse that is not drilled and tapped into the oil galley. The rear hole has a machined surface and is used to mount the pivot ball for a manual transmission clutch release cross-shaft.

© ChevelleWorld
The 4-bolt main block has a 1/2" pipe thread front hole, the center hole is drilled and tapped into the oil galley with a 3/4" pipe thread and the rear hole is 1/2" UNC coarse that is not drilled and tapped into the oil galley. The rear hole has a machined surface and is used to mount the pivot ball for a manual transmission clutch release cross-shaft.

Casting Clock

© ChevelleWorld
The Saginaw foundry casting clock is approximately 2-inches in diameter and is usually found on the rear of the block by the casting number. The clock has 10 dots representing an hour of a shift. The second dot outside the circle indicates the start of a ten-hour shift. The Saginaw foundry usually ran two ten-hour shifts, 7:00 A.M. to 4:00 P.M. and 4:00 P.M. to midnight. Parts cast at the beginning of the shift would have the pointer pointing to the double-dot position as shown in the photo. Every hour the pointer would be moved clockwise to indicate the hour. The slot in the pointer indicates the shift. A flat, slotted head indicates the first shift, the second shift has a round head in the pointer. This pointer indicates this block was cast first hour of the first shift, or 7:00 to 8:00 A.M.

© ChevelleWorld
Note the difference in the Tonawanda foundry casting clock. This clock has 11 dots plus the number 12. The pointer indicates this block was cast in the 8th hour of the shift.

Block Casting Numbers

The block's casting number is generally located on the driver side of the block at the rear where the bellhousing bolts to the block. It's generally thought that the letters "P" and "T" represent "Passenger" and "Truck" but there's no evidence of this as of yet.

Courtesy Chris Holcombe
Another 1968 396 block casting number 3916323 that's much different from the example above.

© ChevelleWorld
1969 396/402 block casting number 3955272 (Note both the "T" above and "P" here were found in Chevelles.)

© ChevelleWorld

1969-1971 427/454 block casting number 3963512 with October 15 casting date on bell housing area.
⁽¹⁰⁾ This 3963512 block dated October 15, 1969 has casting date on bell housing flange and is a warranty block.
Courtesy Todd Burke

Casting Dates

The block's casting date is either on the passenger side of the block at the rear where the bellhousing bolts to the block or on the passenger side of the block near the freeze plug and generally are in the format of a letter for the month, a one- or two-digit number for the day and a single digit number for the year.

It's reported that some early blocks have been found with three digits representing the month, day, and year. These early blocks may also have more than three digits depending on the month and day.

© ChevelleWorld
1968 327 casting date 2 25 8 for February 25, 1968. Note this date begins with the number "2" instead of a letter.

© ChevelleWorld
1969 396 casting date C 14 9 for March 14, 1969 - note this casting date is on the rear of the engine block next to the bellhousing.

Front Cover Dowel Pins

Early (1965-1967) 396 engine blocks did not have alignment dowel pins for the front cover.

Engine Bore and Stroke of 1964-1972 Chevelle Engines - Cubic inches = Bore x Bore x Stroke x .7854 x #cylinders

Cubic Inches	Cylinder Bore	Crankshaft Stroke
194 (I6)	3.564	3.250
230 (I6)	3.875	3.250
250 (I6)	3.875	3.530
283 (V8)	3.875	3.000
307 (V8)	3.875	3.250
327 (V8)	4.000	3.250
350 (V8)	4.000	3.480
396 (V8)	4.094	3.760
402 (V8)	4.124	3.760
427 (V8)	4.250	3.760
454 (V8)	4.251	4.00