Cylinder Block Casting By Year - Generic

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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.

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.

* It's not certain if the late 1969 402 engine was ever 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 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 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.

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.

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.

A little harder to tell on a small block engine but one clue that seems to hold true is this small plug behind the timing chain cover.

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.

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.

1964-1965 327 block casting number 3782870.

1964-1966 283 block casting number 3849852.

1964/1965/1966 283 block casting number 3834810 casting date B 21 6.

1966 396 block casting number 3855961.

1965/1966 396 block casting number 3855962.

1967 327 block casting number 3892657.

1966/1967 396 block casting number 3902406.

1967/1968 396 block casting number 3916323.

This late 1967 396 engine is a 3916323 casting but retains the canister type oil filter.

1968 327 block casting 3914678.

1968/1969 396 block casting 3936440.

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

1969 396/402 block casting number 3955272 (note "T" as opposed to "P" in next photo).

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

1969-1971 427/454 block casting number 3963512 with September 5, 1969 casting date on bell housing area.
⁽¹⁰⁾ This 3963512 block dated September 5, 1969 has casting date on bell housing flange.

1969-1972 402 block casting number 3969854.

1972 block casting number 3999289.

1972 402 block casting number 3999290.

Casting Dates

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.

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

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

1969 396 casting date H 9 8 for August 9, 1968.

1969 396 casting date A 14 9 for January 14, 1969.

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.

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

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

1970 454 casting date of C 31 70 for March 31, 1970.

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

1972 402 casting date of I 20 71 for September 20, 1971.

CE warranty block dated I 6 72 for September 6, 1972

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

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