How to Identify a Small-Block Chevy Engine

Casting numbers say which part a block or head is; the stamp and date code say when and where the engine was built. Start with the VIN for what the car left the factory with, then check the engine itself, since engines get swapped.

Where the numbers are and what they mean

Block casting number — Block casting number: on the ledge (bellhousing flange) at the rear of the block, driver side, behind the number-7 cylinder / driver-side head.
Head casting number — Head casting number and casting date: under the valve cover, in the rocker-arm area (date code near the number). Some later heads repeat the last three digits on a downward-facing ledge on the head ends, readable with a mirror on the engine. Raised end symbols (double hump etc.) give a clue but are shared by several castings.
Format — Cast date code = month letter + day (1-2 digits) + last digit of the year, e.g. B209 = February 20, 1969; C 18 4 = March 18, 1974/1984. Month letters A-L for January-December, with I used for September on cast parts.
Format — Assembly-plant engine code format: plant letter + month (2 digits) + day (2 digits) + suffix letters (no year), e.g. V1012FL = Flint V8 plant, October 12, suffix FL; T0601ED = Tonawanda, June 1, suffix ED. Plant letters: F or V Flint, T Tonawanda. Two-letter suffixes; three-letter suffixes began late in the 1969 model year. The suffix identifies engine, transmission and options for that year and is reused across years, so read it with the casting number and dates.
CE service — Warranty/service engines (from 1968) carry a "CE" stamp: C = Chevrolet, E = engine, one model-year digit, then a 5-digit sequence whose range shows the plant (Flint L6 00001-19999 and 80001-89999, Flint V8 20000-49999, Tonawanda 50000-79999). Example CE900175 = 1969 Chevrolet service engine no. 175 from the Flint L6 plant.
Reman label gen2 — GM remanufactured (service) 4.3L/5.7L L99/LT1/LT4 (Gen II) engines carry their ID label on the LEFT side of the block.

Block casting numbers

Casting	Years	Cubic inches	Main caps	Notes
3892657	1967	302 (Z28), 327, and 1967 Camaro 350	2
3903352	1967	327	2
3914660	1968; 1968-1969	327	2
3914678	1968 (Camaro: 302/327/350);	302, 327, 350	2
3932371	1968/1969-1973	307	2
3932373	1968/1969-1973	307	2
3956632	1969	307	2
3956618	1968-1969	302, 327, 350	2 or 4
3970010	Late 1969 through the 1970s	350 mostly; 1969 302 (Z28) and 327 also listed	2 or 4	the number alone does not tell 2-bolt from 4-bolt or 302/327/350.

Many castings were used for more than one size, so measure the bore and stroke if in doubt.

Cylinder head casting numbers

Casting	Years	Used on	Chamber (cc)	Valves (in)	Notes
3890462	1966-1967 (CRG: used until about March/April 1967)	327 (and 302 Z28 per CRG)	63.3 / 64	1.94/1.50 (L30/L48) or 2.02/1.60 (Z28, L79);	iron, double-hump end mark; Same casting machined for either valve size.
3917291	1967-1968	327, 302 Z28, 350 (L48)	63.3 / 64.0 / 64	1.94/1.50 or 2.02/1.60	iron, double-hump end mark; First with temperature-sender boss (late 1967).
3927186	1969-1970	350 (L48, L46), 302 Z28	63.3 / 64	1.94/1.50 or 2.02/1.60	iron, smaller double-hump mark; Flint-cast; three accessory holes in the ends from 1969 (CRG).
3947041	1969-1970	350 (L48, Tonawanda-built), 302	63.3 / 64	1.94/1.50	iron, right-angle end mark (no camel hump); CarTech: basically the same as the 186 but without the camel hump symbol.
3932441	1969-1970	350 (LM1, L65)	76 / 76.3	1.94/1.50	iron;
3927185	1969;	327/210, 307	69.6 / 70	1.72/1.50	iron
3917293	1968 (CRG notes a few late 1967)	327/210 (LF7), 307	75.3 / 75	1.72/1.50	iron
3884520	1966-1967;	283	60.5 / 60	1.72/1.50	iron; No accessory bolt holes (pre-1969 head), pressed studs (CarTech photo).
10239906	1996; Vortec 1996-up	350 L31 Vortec ("906")	64	1.94/1.50	iron Vortec, 170 cc intake; Factory (Chevrolet Performance): service Vortec head assembly 12558060 is built from casting 10239906 or 12558062; 64 cc chamber, 1.940/1.500 valves, needs a Vortec-specific intake manifold.
12558062	1998; Vortec 1996-up	350 L31 Vortec truck ("062")	64	1.94/1.50	iron Vortec, 170 cc intake; Factory (Chevrolet Performance): service Vortec head assembly 12558060 is built from casting 10239906 or 12558062; 64 cc chamber, 1.940/1.500 valves, needs a Vortec-specific intake manifold.

How to tell a 302 / 327 / 350 on the same casting

Several 1967-69 castings (3892657, 3914678, 3932386, 3956618, 3970010) were built as 302, 327 or 350; the casting number cannot tell them apart. Use the pad suffix plus crank stroke (302 = 3.00, 327 = 3.25, 350 = 3.48).

How to tell a 1.94 from a 2.02 valve heads (same casting)

Several 64 cc castings (462, 291, 186) were machined for either 1.94/1.50 or 2.02/1.60 valves. On 2.02 heads the valves sit very close together (no room for a dime between them) and the chamber is unshrouded/machined around the intake valve.

How to tell a Factory engine from a service (CE) engine

A CE stamp means a warranty/service replacement engine; its year digit is when the block was stamped, not the car year.