V8 Engine Block Casting Numbers - 1964 through 1972

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 didn't 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.

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 (maybe)
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 Identical to #3914636 except for minor interior casting changes to cylinder wall and water jacket sizing.
3916323 1968 (early) (7) 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.
3969854 1969 (late)
1970
1971
1972
396
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 Corvetter (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
Used only in 2-bolt main configuration and saw heavy truck usage until 1978.
3999290 1972 402 240 Used in some late 1972 Chevelles
330817 1974
1975
400
400
150, 180
175
 
346236 1975 454 215 Mid-year 1975.

(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.

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

(5) In 350cid 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.

(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.

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.

2-bolt main block
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" USS coarse that is not drilled and tapped into the oil galley. This rear hole has a machined surface and is used to mount the pivot ball for a manual transmission clutch release cross-shaft.

4-bolt main block
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 the same 1/2" USS coarse thread used for the manual transmission clutch release cross-shaft.

Casting Clock

Saginaw Casting Clock
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.

Tonawanda Casting Clock
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.

File Photo
1964 283 block casting number 3849852.

03/21/2010
1966 396 block casting number 3855961.

File Photo
1965/1966 396 block casting number 3855962.

File Photo
1967 327 block casitng number 3862657.

03/21/2010
1967 396 block casting number 3902406.

06/17/2011
1968 396 block casting number 3916323.

10/23/2013
1968/1969 396 block casting 3936440.

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

03/21/2010
1969 396 block casting number 3955272.

File Photo
1970 396 block casting number 3969854.

Casting Dates

File Photo
Note casting date of B24 70 on this Chevelle 350 block.

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.

File Photo
1968 396 casting date L 6 7 for December 6, 1967.

03/21/2010
1969 396 casting date H 9 8 for August 9, 1968

08/04/2010
1969 396 casting date A 14 9 for January 14, 1969

February 6, 1970
1970 396 casting date B 6 70 for February 6, 1970. Note 1970 has a 2-digit year code.

File Photo
1970 454 casting date of C 10 70 for March 10, 1970.

File Photo
1970 396 casting date of D 7 70 for April 7, 1970.

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 (L6) 3.564 3.250
230 (L6) 3.875 3.250
250 (L6) 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