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Big & Small Block Heads - 1964-1990

 

Heads 1964 - 1990

Identification

A Big Block Head

Scrape the oily goo off and read the letter at the lower left corner of the head, near the #1 or #8 spark plug hole, a letter about 1.5" high indicates a big block, while a number indicates a small block. Some have an additional letter (an A or B), about 1" high, right next to the letter (or number). This is the quickest, easiest way to get the most information about the engine.

Also, there is a 6-digit casting number, which might be among the rocker pedestals on early or small block heads, but is generally found surrounding the center bottom rocker arm cover bolt, 3 digits on each side, visible with the rocker arm cover in place.

To be absolutely sure, the last 3 digits of this 6-digit casting number are also repeated on the underside of the head, near the intake ports. Don't pay $1000 for 'F' heads with the number '686' on the underside ('E' heads with part of the 'E' ground off)! Look closely for grinding marks, and globs of paint that try to hide any alteration. The date code is the usual 1 to 3 digit numbers, about ¼" in height, in the exhaust port area [??]. Looks like it was a plate screwed to the head mold - the screw heads are visible.

Generally, heads with valve rotators and corresponding deep spring pockets (3/8" wide retainer rather than 1/8" retainer), have induction hardened exhaust seats from the factory. Some heads are rumored to have the rotators on the intake or exhaust values only.

[ Thanks to Chris Witt for this information ]


A Small Block Head

At the lower left corner of the head, near the #1 or #8 spark plug hole, a number about 1.5" high indicates a small block (a letter indicates a big block). Some have an additional letter (an A or B), about 1" high, right next to the number (or letter).

Big Block Head ID/Codes, Casting Numbers

If it's an A, B, or C head, look for the engine unit number/ID code as detailed in the Blocks section under Big Block Unit Numbers. 1967 C heads had this number; 68-9's did not. So, if your C head has a stamped ID like V2023456G in figures about ¼" tall, that'd be from a 1967 400-4V, possibly a W-30. If no such ID is stamped in, then it's either a 68-69 C head, or a 1967 head from the left side of the engine. Check the other end of the other head.

ID/                         Casting
Code  Year(s)    CID  CCs   Number   Notes
 A    '65        400  80    383821   Unique 3/8" stud and nut rocker
                 425                 mounting, using a 3-piece rocker
                                     pivot assembly; all except irrigation
 B    '65        425  80    383821   Later '65 heads. Some use 3-piece
                                     rocker pivot asssembly.
 B    '66        425  80    389395   Toro's and 442's got the big
                                     [2.072"] valves. Some use 3-piece
                                     rocker pivot asssembly.
 C    '67 - '69  425  80    394548   AC '68 H/O's. Toro's and 442's got big.
                 455                 valves. Rumored to flow the best of all BB
                                     heads. Can still be found.
 D*   '68 - '69  400  69.75 400370   W-30 and non-AC '68 H/O's. All big-valve.
                 455  69.75 400370
 E    '68 - '70  455  77,80 403686   455's in general, with 442/Toro's
                                     having big valves.
 F*   '70        455  80    404438   W-30's. All big-valve units.
 G    '71        455  80    409100   Generic 455 use, big valves in the
                                     usual applications.
 Ga   '72        455  80    409100   W-30's. Hardly any, if any at all,
                                     were big-valve units.
 H*   '71        455  80    409160   W-30's. Big Valve units.
 J    '73 - '76  455  80,82 411783   All 445's. 'Smog heads',
                                     restrictive exhaust valve pockets.
                                     No big valve units.
 K**             455  80    413191
 Ka** '73 - '76  455  80    413191   Marine, irrigation, W-30/Toro
                                     replacement head. Most were big
                                     valve units.

Notes:
* These W-30 heads are so rare that they command about $1000/pair. Affordable for accurate restoration.
** While not quite as rare as the other heads, they are generally big valve units.

[ Thanks to Chris Witt, Daren, Joe Padavano for this information ]


Small Block Head ID/Codes, Casting Numbers

ID/                          Casting
Code  Year(s)    CID   CCs   Number   Notes
 1    '64        330         385101   Used ROCKER SHAFTS rather than
                                      pairs on PEDESTALS.
 2    '65        330         ??????   All V-8s now using PEDESTALS.
 3    '66        330   60    389394
 4    '67        330   60    394497
 5    '68 - '69  350   64    397742   Excellent candidate for use today.
                                      Good flowing, and high compression.
 6    '70        350   64    403859   W-31's had larger 2.000 intakes. '69
                                      W-31's?
 7    '71        350   64    409147   W-31's had larger [2.000] valves.
 7A   '72        350   64    409147   The 'A' is a subscript, like ¼"
                                      tall, to lower right of the '7',
                                      like | 7A.
 8    '73 - '76  350   79    411929   Smog heads. Have huge bb-sized 79cc
                                      chambers yielding poor compression
                                      ratios without extremes of
                                      compensation.
 10   '76, '77?  260?  57    550362
 2A   '76 - '81  260         554715   Easy way to ID a 260 engine.
 3A   '77 - '80  350   75    554716
 4A   '77 - '79  403   83    554717   Matches the 4A or 4B block, get it?
                                      Easy way to ID a 403.
 5A   '80 - '84  307   67    3317
      '85 also???
 6A   '85 - ??   307   67    5844
 7A   '85 - '90  307   64    0142     This 'A', and the others from 2A to
                                      6A, is a large capital letter equal
                                      in size to, and immediately adjacent
                                      to the 7, like | 7A.
 D3A             350         3948     Diesel.


Detailed Listing

The 4 or 6 digit casting number is found around the center exhaust side rocker arm cover bolt or among the rockers on really early heads [pre-68]. Really late heads have #'s like 4417 or such, they might be out closer to the top of the exhaust port.

ID Casting # Combustion Camber Intake Valve Exhaust Valve
A 383821 80cc 2.000" 1.625"
1965 400/425 motor. Shallow spring seats. No hard exhaust seats. Unique 3/8" stud and nut rocker mounting, using a 3-piece rocker pivot assembly - may present difficulties in rebuilding or finding parts for the rocker assemblies. There is also another "A" head that has adjustable rockers, and look like Chevy heads that have screw-in studs. There is a single machined flat surface for each pair of stud holes. There are no rockers or pivots. Correct for 1965 442, etc. RH head will have the engine ID code stamped into the front.

B 389395 80cc 2.000, 2.072" 1.625"
1966 400/425's. Toronado and 442 heads had the larger 2.072" intake valves. The 1966 Tri-carb and W-30's used what's called a -1 (dash one) head. That is that the casting number is followed by a -1. Shallow spring seats. No hard exhaust seats. RH head will have the engine ID stamped into the front. First to use the one piece aluminum rocker pivots with 5/16" mounting bolts. Some early ones used the 3 piece rocker arm pivots with studs.

C 394548 80cc 2.000, 2.072" 1.625"
67-69 400/425/455's [except W-30 and most Hurst/Olds], including 1968 H/O with A/C. Valves commonly 2.000" and 1.625", but Toronado and 442 [except Turnpike Cruiser] heads had the larger 2.072" intakes. Presumably the H/O with C heads also had the large valves. Shallow spring seats. No hard exhaust seats. On 1967 engines, RH head will have the engine ID stamped into the front. Correct for 67-69 442's, even 68 H/O with air. Heads for 1967 W-30 or California cars had the A.I.R. passages [that boss on the exhaust port] drilled, tapped, and plugged. Some '68-9 442's with auto trans may have had small valves. This is reputed to be the best-flowing head, and is still fairly easy to find.

*D 400370 69.75cc 2.072" 1.625"
68-69 400/455's, with W-30 or H/O [except A/C '68 H/O's- see C]. Large valves, 2.072 and 1.625". Shallow spring seats. No hard exhaust seats [?]. Rumored that the '68 versions had both center exhaust ports connected to the crossover, whereas an improved later version as used in 1969 had one port blocked off from the intake heat crossover port for better power. 'Improved port configuration for better flow"- according to Supercars Unltd. book 442 by the Numbers. Very rare and valuable.

E 403686 77, 80cc 2.000, 2.072" 1.625"
1970 455's, except W-30. Valves commonly 2.000 and 1.625", but Toronado and 442 heads had the larger 2.072" intakes. Valve rotators on all valves, therefore deep spring seats. Maybe have hardened exhaust seats.

*F 404438 80cc 2.072" 1.625"
1970 455's with W-30. Large valves, 2.072 and 1.625". Maybe have hardened exhaust seats. Valve rotators on all valves, therefore deep spring seats. One center exhaust port blocked off from the intake heat crossover port for better power. 'Improved port configuration for better flow"- according to Supercars Unltd. book 442 by the Numbers. Very rare and valuable. *THE* head to get, if cost is no object, or for an investment. Watch out for an E ground to look like an F; check the 6-digit casting number and the 3 digits on the underside as well (should not be 686). Always look for the two raised ribs on the end of the head that are nearly impossible to duplicate, even with JB weld. Only F heads had these ribs, never E's.

G 409100 80cc 2.000, 2.072" 1.625"
1971 455's, except W-30 [see H]. Valves commonly 2.000 and 1.625", but Toronado and 442 heads had the larger 2.072" intakes. Common heads use valve rotators on all valves, but 442 [and Toro?] heads used rotators on exhaust valves only- according to 442 by the Numbers. Wherever rotators are used, the thick rotator/retainer required the use of a deep spring seat. Maybe hard exhaust seats.

Ga 409100 [same number as G head] 80cc 2.000, 2.072" 1.685"
1972 455's, including W-30. Valves almost universally 2.000 and 1.625", even 442's had small intakes, if auto trans models. Even the Toronados were relegated to small intake valves this year. Only 442's with W-30 or MT had the larger 2.072" intakes. No way to tell valve size without measuring a valve. Strange combinations of exhaust valve sizes and angles, depending on application. Exhaust valve with a unique 1.685" diameter and 30 degree face. All Ga heads use valve rotators on all valves, therefore have all deep spring seats. Hard exhaust seats.

*H 409160 80cc 2.072" 1.625"
1971 455's with W-30. Large valves, 2.072 and 1.625". Valve rotators on all valves, therefore deep spring seats. Maybe have hardened exhaust seats. One center exhaust port blocked off from the intake heat crossover port for better power. 'Improved port configuration for better flow"- according to Supercars Unltd. book 442 by the Numbers. Improved *over what* they don't say. Very rare and valuable.

J 411783 80, 82cc 2.000" 1.625"
1973-76 455 "smog" motors. Standard [small] valves: 2.000 and 1.625", even Toronado, 442, etc. [presumably]. Exhaust port is choked off to about 1" diameter just under the valve. No blocked heat crossover. Rotators, deep spring seats, hardened exhaust seats. Very common. Avoid.

*K, Ka 413191 80cc 2.072" 1.625"
1973-76 factory W-30/ Marine/ Irrigation head replacement unit. Rumored to have possibly been supplied as original equipment on some '72 W-30's. Accepted by the NHRA as a stock W-30 head. Large valves, 2.072 and 1.625". Big 80cc chambers which yields poor compression figures, but so are the C's, etc. unless you shave them. Rumored to flow not quite so well as C's [source: Mondello]. Valve rotators on all valves, therefore deep spring seats, allowing either rotator retainers or very stiff springs. Hardened exhaust seats. Exhaust heat crossover is NOT blocked off. Not quite so rare or expensive as the other 'exotics' (F, H's). Also said to be found in 1973-1974 standard shift big blocks found in Cutlass'.

ID Casting # Combustion Camber Intake Valve Exhaust Valve
1 385101
The rocker assembly is the same as later non-adjustables, except the aluminum cross pieces are stamped steel, and don't bottom out on the head. The pivots are individual and made of steel; they are linked together by the steel cross piece. These are adjustable rockers.

2

3 389394 60cc

4 394497 60cc

5 397742 64cc 1.875 1.562

6 403859 64cc 1.995 1.624

7 409147 64cc 1.995 1.624

7A 409147 64cc 1.875 1.502

8 411929 79cc 1.875 1.622

10 550362 57cc 1.517 1.305
260 only.

2A 1.517 1.305
260 only.

3A 554716 75cc 1.880 1.507

4A 554717 83cc 2.000 1.507
1977 - 79 403's only. This head's BB size chambers will reduce the CR (and power) of other SBs.

5A 3317 67cc
Used on the regular hydralic lifters engines. This head is preferred for 307 performance use because there are port matching problems between aftermarket intakes and exhaust headers with the 7a heads. 5a heads are rumored to flow slightly better. The 5a ports are larger than the 7a's, so this makes sense. So, if you switch from 7a to 5a heads you should get the intake and exhaust manifolds from the donor engine.

6A 5844 67cc

7A 0142 64cc
Used on the newer hydraulic roller-lifter engine. Possible port matching problems with aftermarket intakes and exhaust headers. Rumored to flow slightly less than 5a heads. The 7a's ports are smaller than the 5a's (about ½ the size of typical 350 ports), so this makes sense.

D3A 3948 1.875 1.622
The 350 Diesel used intake 1.875 and exhaust 1.622 in all applications. Flat chambers for 22.5:1 compression!


Notes:
* - F,K,H,D... almost makes a word...
These are the 'exotic' rare, W-30/Marine/Irrigation heads, worth a bundle if you can find them. Usually indicates a W-30 engine or one that someone cared about a great deal. Wonderful things to have. Tough part is affording them, at about $1000 a pair, except for the K's, which are maybe half that. All are big valve units. May have been milled at the factory for smaller combustion chambers, therefore higher compression. D heads are rumored to come in 2 forms: with heat crossover blocked from one center exhaust port, and without this feature. The F and H heads also have blocked exhaust crossover passage, but K's do not.

There has been a lot of talk that C heads are the BB head of choice. #5, 6, and 7 units are the best readily available units for small blocks. Of course, if you find a set of W-30 or W-31 heads for cheap, with the exhaust heat crossover blocked and all that. A set of D/F/H heads were recently commanding over $1000/pair, and needed rebuild at that. C's start to look real good, and you can still find those.

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