SBC cylinder head identification
Most cylinder heads are identified in a general sense from simply looking at them. But just knowing the generic type of engine does not begin to tell the whole story. There are a wide variety of heads for most any given engine type and in many cases there's a lot of difference between them in their potential for performance.
Basics of cylinder head identification
A big block Chevy (BBC) or small block Chevy (SBC) head is readily recognized by the majority, as are Hemi heads, small block Ford (SBF) heads, and depending on experience and engine preferences, others as well.
To distinguish the nuances, there are several things that can be used to ID cylinder heads:
- Casting number
- Usually cast into the head as opposed to being stamped, the casting number is usually the best thing to use to tell what a cylinder head was originally used on and its potential for performance use.
- The casting number may be out in the open where it can be easily seen, like the Pontiac V8, or somewhat harder to see but still visible without taking anything off the head, or the number can be under the valve cover or under the head where it's difficult to see without some amount of disassembly.
- Casting date
- Like casting numbers, the date code is usually cast into the head, and may or may not be visible without removing the valve cover.
- Secondary identifier(s)
- These are often stamped in instead of cast, like in the case of some 1970's Pontiac heads.
- Casting identifiers
- This is different shapes that may be (in the case of the SBC) on the end of the heads or elsewhere.
Located under the valve covers, the casting number is the best way to ID a SBC head. The number along with the date code can be used to pinpoint the heads original application fairly closely. Valve sizes (1.94" intake x 1.5" exhaust or 2.02" intake x 1.60" exhaust) and whether or not screw-in studs and guide plates are in place can further ID them. Be aware that screw-in studs/guide plates were not used on all, or even most, large valve SBC performance heads from the factory, and if present, they could very well have been added previously.
Through the years, small block Chevy heads have been ID'd by the head's end casting shapes. They don't usually tell the exact details like valve sizes but are useful for telling (at least potentially) a performance head from a non performance head. A casting identifier can differentiate between a large or small combustion chamber volume, also intake port volume, spark plug type (gasketed or tapered seat), whether they were used with a certain type of front accessory arrangement (short or long water pump for instance).
The most recognized end casting identifier of the SBC heads is the "fuelie", "double hump", or "camel hump". It got the name fuelie from the fact that it was used on the fuel injected Corvette engines. Double hump and camel hump is from the physical shape of the casting. The fuelie heads was used from the 1960's to the 1970's on the high performance optional engines up to and including the 375 HP fuel injected L-84 327 cid engine, and the 365 HP L-79 4-barrel engine of 1964, and the bad-to-the-bone LT-1 engine, to name just three.
462 is the most-used SBC head casting number out there- at least six different SBC cylinder head casting numbers end in 462, according to 'the books':
Diagrams of some common small block Chevy head ID castings
- A- Rectangle c/n 460, 1955 & up 265/283, 8:1 CR, 1.72" x 1.50" valves.
- B- Narrow triangle over rectangle c/n 520, 896, 1958 and up 283 PowerPak and 1957-'60 FI. 9.25:1 CR, 1.72" x 1.50" valves, 59cc nominal chamber volume. Could be used on a 305 but no accessory holes and has unhardened exhaust seats.
- C- Vertical bar over rectangle c/n 997, 1957 Corvette 270 HP, 9.5:1 CR, chamber similar to PowerPak but with sharp corners in plug area.
- D- 2 vertical bars over rectangle, c/n 997, 1956 Corvette 2X4-bbl 283; 1958 passenger car FI; chamber same as 1957 270 HP Corvette.
- E, F- Large “camel hump” c/n 291, 461, 461X, 462. High performance or “fuelie” heads, chamber sizes are 62-64 cc nominal, came with either 1.94" x 1.50" or 2.02" x 1.60" valves, c/n 291 on 327 through 1968, has temperature gauge sender hole; 462 do not have temp sender hole.
- G- Left-facing right triangle c/n 041, 1969-'70 350/300HP, accessory bolt holes, most have 1.94" x 1.50" valves
- H- Small “camel hump” c/n 186, 492. Later high performance or “fuelie” heads, some c/n 186 (1969 and later) and all c/n 492 have accessory bolt holes. Either 1.94" x 1.50" or 2.02" x 1.60" valves, 64cc nominal chamber volume. 1970 LT-1/Z-28 use c/n 492. Available as p/n 3987376.
- I- Large triangle over rectangle (“crown”) c/n 882. Large chamber (76 cc nominal), hardened exhaust valve seats, compromised intake port (1971-'76 350/400 cid). One of the most common smog heads, performance use is limited.
- J- No casting identifier c/n 113, 1986-'90 Corvette and GMPP 350 HO, aluminum with no exhaust heat cross over, 58cc chamber, 1.94" x 1.50" valves, centerbolt valve covers, good 305 or light performance 350 street head especially if ported, 1988-on have raised D-shaped exhaust port, 3/8" screw-in studs and guide plates.
- K- 3 right-facing “stairs” (“bench” on intake runner) c/n 487. 1971-'76 76 cc, said by many to be the best large chamber head. 1.94" x 1.50" or 2.02" x 1.60" valves were used, big valve heads machined for screw-in studs and guideplates.
- L- Right-facing “bench” c/n 993. Common large chamber smog head, not a lightweight casting. Similar to c/n 487. Used on the SBC 400, so may have steam holes and 1.60" exhaust valves. Hardened exhaust seats.
- M- One triangle c/n 882. Alternative marking for 882 (see I above). Hardened exhaust seats.
- N- 2 triangles c/n 624. Late model lightweight casting version of c/n 882. Said to be crack prone. Used on Corvette and Camaro high performance engines with 2.02" x 1.60" valves. Hardened exhaust seats.
- O- “Saddle” and vertical bar c/n 416. Late-model 305, conventional perimeter valve cover, intake port not restricted, lightweight, 57 cc nominal chamber volume. Hardened exhaust seats.
- P- Double (Captain’s) bars c/n 193. Used on TBI equipped engines. Mid-1980- up style centerbolt valve cover. Has restrictive vane cast in intake port to induce swirl/turbulence. Not usually recommended for high RPM performance applications unless serious port work is done. Hardened exhaust seats.
Vortec L30 5.0L heads
Vortec L31 5.7L heads
The L31 5.7L Vortec casting numbers are 12559062 and 10239906.
SBC heads to avoid
The c/n 462624 is said to be very prone to cracking. Even though they can be found fitted with 2.02" x 1.60" valves and screw in studs/guide plates from the factory, they still are not a good choice for serious performance use.
1971-up heads with casting numbers 882, 993, 487, 336 can have 3/8" exhaust stems as well as 1.72" intake valves. Heavy 20-30 Series truck use, mainly. Both small 1.72" intake and 3/8" stem exhaust valves may be found on c/n's 261, 624. Also 1987-'95 center bolt v-cover-type head # 14102191 can have the 3/8" exhaust valve.
Usually swirl port TBI SBC heads are not used in high performance applications because they run out of breath earlier than the RPM most performance camshafts need to make peak power. Some casting numbers for them are 187, 191, 193. Similar heads, but without the swirl-inducing vane are c/n's 14011083 and 14096217.