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Or for a list of all the codes just hit the Submit button.
| Pontiac Cylinder Head Search Interface |
Chart to mill Pontiac Cylinder Heads
Chart of C.R. of Pontiac Engines and Heads
C.R. Percent Power Loss
Pontiac made closed chambered heads until 1967.In 1967 Pontiac made some open chamber heads(i.e. 061).After 1967 the heads were open chamber heads.
| Exhaust Crossover Port Matchings |
| With Head | And Manifold | Use Gasket |
| 1965-71 | 1965-71 | 1965-71 |
| 1965-71 | 1972-79 | 1972-79 |
| 1972-79 | 1972-79 | 1972-79 |
| 1972-79 | 1965-71 | 1965-71** |
** Use sheet stainless steel block off plate.
In 1973 Pontiac started stamping extra numbers (1/4" tall) on their heads.These head numbers represented chamber sizes.They are usually stamped on the machined pads by the valve covers.
Head ID Location Picture
1973/74 Stampings on Head codes - 4X, 46, 4C, 16/X
| Stamped ID |
Head # Code |
MVMA Chamber Vol. |
Valve Diameter |
Valve Length |
CID |
| 1 / 1H | 4X | 112.30 cc's | 2.11/1.66 valve | 4.78" | 455 |
| 2H | 46 | 96.17 cc's | 1.96/1.66 valve | 4.86" | 350 |
| 3 / 3H | 4X | 98.21 cc's | 2.11/1.66 valve | 4.86" | 400 |
| 4 / 4H | 4X | 98.94 cc's | 1.96/1.66 valve | 4.86" | 350/400 |
| 5H | 4C (AIR) | 96.17 cc's | 1.96/1.66 valve | 4.86" | 350 |
| 6H | 46 | 96.17 cc's | 1.96/1.66 valve | 4.86" | 350 |
| 6H | 16/X | 110.74 cc's | 2.11/1.77 valve | 4.97" | 455 SD |
| 7 / 7H | 4X | 98.21 cc's | 2.11/1.66 valve | 4.86" | 400 |
| 8 / 8H | 4C (AIR) | 98.94 cc's | 1.96/1.66 valve | 4.86" | 400 |
*All rocker arms are threaded beginning with Motor Unit Number 709986 assembled on or about May 7, 1973.
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5C heads were installed on engines until around mid 1975 then dropped
-5C-4- 1975 350 4bbl, 2.11/1.66" valves, 4.960/4.949" valve length,
30/45 degree seats, threaded studs, 93cc
-5C-7- 1975 350 4bbl AIR, 2.11/1.66" valves, 4.960/4.949" valve length,
30/45 degree seats, threaded studs, 93cc
-5C-8- 1975 400 4bbl, 2.11/1.66" valves, 4.960/4.949" valve length,
30/45 degree seats, threaded studs, 101cc
-5CX-8- 1975 400 4bbl, 2.11/1.66" valves, 4.960/4.949" valve length,
30/45 degree seats, threaded studs, 101cc
-5C-9- 1975 400 4bbl AIR, 2.11/1.66" valves, 4.960/4.949" valve lengths,
30/45 degree seats, threaded studs, 101cc
5I (51) heads for the 455:
-5I-6- 1975 455 4bbl 2.11/1.66" valves, 30/45 degree seats, threaded studs, 124cc
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The 6X castings started being installed on engines after about 2/21/75
(cc's are factory reported, may actually be different)
6X-4 350(and 77-79 T/A 6.6), 93cc, 2.11/1.66"
6X-6 455, 114cc ? /124cc, 2.11/1.66"
6X-8 400, 101cc, 2.11/1.66"
6H-6 455, 124cc, 2.11/1.66"
6S-7 350 w/AIR, 93cc, 2.11/1.66"
6S-9 400 w/AIR, 101cc 2.11/1.66"
The 6X-4 and 6X-8 were the only heads used after 1976.
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Stampings on 46 Head Code
Just some more codes and sub codes for the 46's.One set is from a "WP" 74 GTO,
one set
from a 74 "YS" GTO 350 and 1 from a "ZB".Very interesting.All small
valve of course.
WP HEADS YS ZB
screw in studs same pressed
"6H" sub code "H6" subcode no subcode
K093-K133 date codes K093-K103 I103-I213
3.170"wide scallop 3.230" wide same
.970" deep scallop 1.060" deep same
Seems Pontiac followed tradition in the fact that auto's got a little
less cr than stick.Contrary to belief,48/62/16/12/13 are all rated
72cc.Not true.12 and 48 are 8-10cc less than the auto heads.
(Let me know if you find any more information on these codes or any not listed.)
Pontiac Intake Manifold Years Interchange
1957-1958
1959-1960
1961-1964
1965-1979
Does not apply to 301 or the RA V
