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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
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| 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. |
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| 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. |
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| 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. |
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| *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. |
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| 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. |
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| *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. |
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| 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. |
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| 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. |
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| *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. |
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| 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. |
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| *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'. |
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| ID | Casting #
| Combustion Camber | Intake Valve | Exhaust Valve |
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| 1 | 385101 | | | |
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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.
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| 3 | 389394 | 60cc | | |
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| 4 | 394497 | 60cc | | |
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| 5 | 397742 | 64cc | 1.875 | 1.562 |
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| 6 | 403859 | 64cc | 1.995 | 1.624 |
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| 7 | 409147 | 64cc | 1.995 | 1.624 |
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| 7A | 409147 | 64cc | 1.875 | 1.502 |
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| 8 | 411929 | 79cc | 1.875 | 1.622 |
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| 10 | 550362 | 57cc | 1.517 | 1.305 |
| 260 only. |
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| 2A | | | 1.517 | 1.305 |
| 260 only. |
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| 3A | 554716 | 75cc | 1.880 | 1.507 |
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| 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. |
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| 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. |
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| 6A | 5844 | 67cc | | |
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| 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. |
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| 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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