The information below reflects the research conducted by Pontiac enthusiast/ author Pete McCarthy, much of which is from his book, Pontiac Musclecar Performance 1955-1977, as well as information gathered from many other Pontiac enthusiasts world-wide. Information about PMD heads is still being gathered. What is apparent is that while Pontiac had policies and specifications, both seemed to fluctuate as need be to build engines and place them in passenger cars.
Chamber size of heads is given as an approximate CC as is static compression. When examining any Pontiac head today it requires an open mind. All chamber sizes should not be assumed but cc’d to confirm the chamber size. I wish to point out that Pontiac manufactured heads with push-in studs and screw-in studs using guide plates. Most if not all performance heads used screw-in studs. Today machinists can easily improve on any stock iron Pontiac head with the inclusion of hardened seats, screw-in studs, longer valves, taller installed height for after market springs working with high lift camshafts.
Porting remains a viable means of improving flow for increased power. Most importantly, one must know the overall condition of the heads before attempting any performance modifications. Be sure to have them cleaned and magnufluxed by a competent machine shop.
If you have any information that may be useful in improving this head chart, please email me at: bboyle@boyleworks.com
|
Year |
CID |
Advertised HP |
Head casting # |
Valve Sizes intake/exhaust |
Approx CC or static CR |
|
1959 |
389 |
215-345 hp |
531395 |
1.88/1.60 |
69 |
|
1960 |
389 |
215-345 hp |
536109 |
1.88/1.60 |
69 |
|
389SD |
348-363 hp |
535461 |
1.92/1.60 |
69 |
|
|
1961 |
389 |
all |
538177 |
1.88/1.60 |
69 |
|
421 |
all |
538177 |
1.88/1.60 |
69 |
|
|
389SD |
368/373 hp |
540306 |
1.92/1.66 |
68 |
|
|
421SD |
368/373 hp |
540306 |
1.92/1.66 |
68 |
|
|
1962 |
389 |
all |
538177 |
1.88/1.60 |
69 |
|
421 |
all |
538177 |
1.88/1.60 |
69 |
|
|
389SD |
385/405 hp |
540306/544127 |
1.92/1.66;2.02/1.76 |
68 |
|
|
421SD |
385/405 hp |
540306/544127 |
1.92/1.66;2.02/1.76 |
68 |
|
|
1963 |
326 |
250 hP |
543797 |
1.88/1.60 |
8.6 cr |
|
326 |
260/280 hp |
548232 |
1.88/1.60 |
10.25 cr |
|
|
389 |
215/230/235 hp |
543796 |
1.88/1.60 |
8.6 cr |
|
|
389 |
267/283/303/313 hp |
543797 |
1.88/1.60 |
10.25 cr |
|
|
421 |
320 hp |
543797 |
1.88/1.60 |
10.75 cr |
|
|
421 |
353/370 hp |
9770716 |
1.92/1.66 |
72 |
|
|
421SD |
390/405/410 hp |
544127/9771980 |
2.02/1.76 |
64 |
|
|
1964 |
326 |
250 hp |
9773345 (845) |
1.88/1.60 |
8.6 cr |
|
326 |
280 hp |
9773395 |
1.88/1.60 |
10.0 cr |
|
|
389 |
215/230/235 hp |
5437796 |
1.88/1.60 |
8.6 cr |
|
|
389 |
267/283/303/306 hp |
9773345/(845) |
1.92/1.66 |
10.5 cr |
|
|
421 |
320 hp |
9773345/(834) |
1.92/1.66 |
10.75 cr |
|
|
389 |
325/330/348 hp |
9770716 |
1.92/1.66 |
72 |
|
|
421 |
350/370 hp |
9770716 |
1.96/1.66 |
68 |
|
|
1965 |
326 |
250 hp |
62 |
1.88/1.60 |
8.6 cr |
|
326 |
285 hp |
22 |
1.88/1.60 |
10.5 cr. |
|
|
389 |
256 hp |
75 |
1.88/1.60 |
8.6 cr |
|
|
389 |
290/325/333 hp |
76 |
1.92/1.66 |
10.5 cr. |
|
|
389 |
335/338/360 hp |
77 |
1.92/1.66 |
10.5 cr |
|
|
421 |
338 hp |
76 |
1.92/1.66 |
10.75 cr. |
|
|
421 |
356/376 hp |
77 |
1.92/1.66 |
10.75 cr |
|
|
1966 |
326 |
250 hp |
94 |
1.88/1.60 |
8.6 cr |
|
326 |
285 hp |
95 |
1.88/1.60 |
10.5 cr |
|
|
389 |
256 hp |
91 |
1.92/1.66 |
8.6 cr |
|
|
389 |
290/325/333 hp |
92 |
1.92/1.66 |
10.5 cr |
|
|
389 |
335/360 hp |
93 |
1.92/1.66 |
10.5 cr 68cc |
|
|
421 |
338/350 hp |
92 |
1.92/1.66 |
10.75 cr 70 cc |
|
|
421 |
356/376 hp |
93 |
1.92/1.66 |
10.75 cr 68 cc |
|
|
1967 |
326 |
250 HP |
140 |
1.92/1.64 |
9.2 cr |
|
326 |
285 HP |
141 |
1.92/1.64 |
10.5 cr |
|
|
400 |
255/260/265 HP |
142 |
1.92/1.64 |
8.6 cr |
|
|
400 |
290 HP |
143/061 |
1.92/1.64 |
10.5 cr. |
|
|
400 |
325/333 HP Big Car |
143/061 (closed chamber) |
1.92/1.64 |
10.5 cr |
|
|
400 |
350 HP (GP) |
670/9787671/187 |
2.11/1.77 |
72 cc |
|
|
400 |
325/335/360 HP |
670 (closed chamber) |
2.11/1.77 |
72 cc |
|
|
400 |
325/360 HP RA |
670/97 (closed chamber) |
2.11/1.77 |
72 cc |
|
|
428 |
360/376HP |
670/9787671 (closed) |
2.11/1.77 |
72 cc |
|
|
1968 |
350 |
265 HP |
17 |
1.96/1.66 |
8.6 cr |
|
350 |
320 HP |
18 |
1.96/1.66 |
10.5 cr |
|
|
400 |
265 HP |
14 |
1.96/1.66 |
8.6 cr |
|
|
400 |
290/340 HP Big Car |
15/215 |
1.96/1.66 |
10.5 cr |
|
|
400 |
350 HP (GP) |
16/ 216/ 62 |
2.11/1.77 |
72-75 ccs |
|
|
400 |
330 HP (FB) |
16/ 216/ 62 |
2.11/1.77 |
72-75 ccs |
|
|
400 |
335/350/360 HP |
16/ 62 |
2.11/1.77 |
72-75 ccs |
|
|
400 |
335/360 HP RA I |
31/ (37) |
2.11/1.77 |
72 cc |
|
|
400 |
340 (FB) /366 (GTO) |
R/96/ A (RA II) (rd port) |
2.11/1.77 |
72 cc |
|
|
428 |
375 HP |
16/ 216 |
2.11/1.77 |
72 cc |
|
|
428 |
390 HP |
16/ 216 |
2.11/1.77 |
72 cc |
|
|
1969 |
350 |
265 HP |
47 |
1.96/1.66 |
8.6 cr |
|
350 |
325 HP |
48 |
2.11/1.77 |
10.5 cr. |
|
|
400 |
265 HP |
45 |
1.96/1.66 |
8.6 cr |
|
|
400 |
290 HP |
46 |
1.96/1.66 |
10 cr |
|
|
400 |
340 HP (GP) |
16/ 62 |
2.11/1.77 |
72 cc |
|
|
400 |
330,335,350/ 366 HP |
16/ 62/ 48 (MT) |
2.11/1.77 |
72cc |
|
|
400 |
345(FB) /370 (GTO) |
722 (RA-IV) |
2.11/1.77 |
71 cc |
|
|
428 |
360 HP |
16 (small-valve ) 46 |
1.96/1.66 |
10 cr |
|
|
428 |
370 HP (GP) |
62 |
2.11/1.77 |
72 cc |
|
|
428 |
390 HP |
16/ 62 |
2.11/1.77 |
72 cc |
|
|
400 |
375 HP(RA-V) |
44 Tunnel Port |
2.11/1.77 |
67 cc |
|
|
303 |
RA=V Tunnel Port |
546184 |
2.11/1.77 |
56 cc |
|
|
1970 |
350 |
255 HP |
11 |
1.96/1.66 |
8.8 cr |
|
400 |
265 HP |
11 |
1.96/1.66 |
8.6 cr |
|
|
400 |
290 HP |
16 (small valve) |
1.96/1.66 |
10 cr |
|
|
400 |
330 HP Big Car |
16 |
1.96/1.66 |
10 cr |
|
|
400 |
330 HP |
12 (MT) |
2.11/1.77 |
72 cc |
|
|
400 |
330 HP |
13 (AT) |
2.11/1.77 |
72 cc |
|
|
400 |
345 HP(FB/RAIII) |
12 |
2.11/1.77 |
72 cc |
|
|
400 |
350 HP (GP) |
13 |
2.11/1.77 |
72 cc |
|
|
400 |
350 HP (GTO) |
12 (MT) |
2.11/1.77 |
72 cc |
|
|
400 |
350 HP (GTO) |
13 (AT) |
2.11/1.77 |
72 cc |
|
|
400 |
366 HP (GTO) |
12 (RA III) |
2.11/1.77 |
72 cc |
|
|
400 |
370 HP (RA IV) |
614 (Round Ports) |
2.11/1.77 |
71 cc |
|
|
455 |
360 HP Big Car |
15 |
1.96/1.66 |
87 cc |
|
|
455 |
360/370 HP (GTO/GP) |
64 |
2.11/1.77 |
87 cc |
|
|
1971 |
350 |
250 net HP |
94 |
1.96/1.66 |
96 cc |
|
400 |
265 net HP |
99 |
1.96/1.66 |
98 cc |
|
|
400 |
300 net HP |
96 |
2.11/1.77 |
96 cc |
|
|
455 |
280 net HP |
98 |
1.96/1.66 |
114 cc |
|
|
455 |
325 net HP |
66 |
2.11/1.77 |
114 cc |
|
|
455 |
335 net HP (455HO) |
197(191) (Round Ports) |
2.11/1.77 |
111 cc |
|
|
1972 |
350 |
175 net HP |
7H1 |
1.96/1.66 |
7.6 cr |
|
400 |
200 net HP |
7J2 |
1.96/1.77 |
8.4 cr |
|
|
400 |
250 net HP |
7K3 |
2.11/1.77 |
96 cc |
|
|
455 |
200 net HP |
7L4 |
2.11/1.77 |
114 cc |
|
|
455 |
250 net HP |
7M4 |
2.11/1.77 |
114 cc |
|
|
455 |
250 net HP |
7M5 |
2.11/1.77 |
114 cc |
|
|
455 |
300 net HP(455HO) |
7F6 (Round Ports) |
2.11/1.77 |
111 cc |
|
|
1973 |
350 |
150/175 net HP |
46/4C |
1.96/1.66 |
96 cc |
|
400 |
170/185 net HP |
46/4C |
1.96/1.66 |
98 cc |
|
|
400 |
200 net HP |
4x/4C |
2.11/1.66 |
98 cc |
|
|
400 |
230 net HP (AT) |
4X-7H screw-in studs likely |
2.11/1.66 |
98 cc |
|
|
455 |
215/250 net HP |
4X-1H screw-in studs likely |
2.11/1.66 |
114 cc |
|
|
455 |
290 net HP (455SD) |
16 (Round Ports) |
2.11/1.77 |
111 cc |
|
|
1974 |
350 |
155/170 net HP |
46/4C |
1.96/1.66 |
7.6 cr |
|
350 |
200 net HP (GTO) |
46 (screw-in studs) |
1.96/1.66 |
7.6 cr |
|
|
400 |
175/190 net HP |
46/4C |
1.96/1.66 |
8.1 cr |
|
|
400 |
200 net HP |
4X-4H/4C |
1.96/1.66 |
99 cc |
|
|
400 |
225 net HP (AT) |
4X screw-in studs likely |
2.11/1.66 |
98 cc |
|
|
400 |
225 net HP (AT) |
4C |
2.11/1.66 |
98 cc |
|
|
400 |
225 net HP (MT) |
4X-3H screw-in studs |
2.11/1.66 |
98 cc |
|
|
455 |
215/250 het hp |
4X-1H screw-in studs likely |
2.11/1.66 |
114 cc |
|
|
455 |
215/250 net hp |
4C |
2.11/1.66 |
114 cc |
|
|
455 |
290 net HP (455SD) |
16 (Round Ports) |
2.11/1.77 |
111 cc |
|
|
1975 |
350 |
ALL |
5c/ 6X |
2.11/1.66 |
7.6 cr |
|
400 |
ALL |
5c/ 6X |
2.11/1.66 |
7.6 cr |
|
|
455 |
AIR |
6S |
2.11/1.66 |
7.6 cr |
|
|
350 |
HO non-air |
6H |
2.11/1.66 |
7.6 cr |
|
|
1976 |
350 |
ALL |
6X-4/ 6S |
2.11/1.66 |
7.6 cr |
|
400 |
ALL |
6X-8/ 6S |
2.11/1.66 |
7.6 cr |
|
|
455 |
AIR |
6S |
2.11/1.66 |
7.6 cr |
|
|
455 |
HO non-air |
6H |
2.11/1.66 |
7.6 cr |
|
|
1977 |
301 |
ALL |
1 |
1.72/1.50 |
8.2 cr |
|
350 |
ALL |
6X-4/ 6S |
2.11/1.66 |
7.6 cr |
|
|
400 |
180 hp |
6X-8 |
2.11/1.66 |
7.6 cr |
|
|
400 |
200 hp |
6X-4 |
2.11/1.66 |
8.0 cr |
|
|
1978 |
301 |
ALL |
01-Feb |
1.72/1.50 |
8.2 cr |
|
350 |
ALL |
6X-4/ 6S |
2.11/1.66 |
7.6 cr |
|
|
400 |
180 hp |
6X-8 |
2.11/1.66 |
7.6 cr |
|
|
400 |
220 hp |
6X-4 |
2.11/1.66 |
8.1 cr |
|
|
1979 |
301 |
ALL |
1 |
1.72/1.50 |
8. 2 cr |
|
400 |
220 hp (MT only) |
6X-4 |
2.11/1.66 |
8.1 cr |