Butler Performance · Pontiac Tech

Pontiac Cylinder Head Identification

Pontiac heads are identified by a short casting code cast near the valve covers — not the full part number. The code tells you the year, application, chamber size, port type, and valve sizes that decide your compression, intake, and header fitment. Use the chart below to pin down what you have.

D-Port vs Round-PortChamber cc · valve sizeCross-checked vs Wallace Racing

Start Here

Identifying Your Heads

1 · Find the casting code

A short 2–3 character code (e.g. 670, 16, 6X, 7F6) is cast on the machined pad by the valve covers / center exhaust ports. From 1973 on, Pontiac also stamped a 1/4" chamber-size sub-ID on the pad.

2 · D-Port or Round-Port?

D-Port exhaust looks like two D’s back-to-back and takes a standard D-port header flange. Round-Port (Ram Air IV / 455 HO / SD) looks like a sideways “D” pointing up and needs a round-port flange. They are not interchangeable.

3 · Read the valve size

Big-valve heads run a 2.11" intake; 350 heads run a 1.96" intake. The exhaust valve is the catch — see the rule below.

The Valve-Size Rule (read this before trusting any blanket chart)

1967–1972 big-valve

400 / 428 / 455 heads: 2.11 / 1.77

1973–1979 big-valve

400 / 455 D-port: 2.11 / 1.66 — exhaust valve was reduced to 1.66 in 1973

350 heads (all years)

1.96 / 1.66 — not 2.11/1.77, despite some published charts

455 SD & RA V

SD (73–74) keeps 2.11 / 1.77; RA V tunnel-port is 2.19 / 1.77

The old “all 1967-and-up heads are 2.11/1.77” shorthand is only true through 1972. Every row in the chart below lists the actual valve size so you don’t have to rely on the shorthand.

Master Reference

Pontiac Head Chart

Early Heads · 1958–1966

First-generation small-valve castings.

Code	Year	Application	Chamber cc	Port	Valves int/exh	Notes
528511	1958	370	62	D-Port	1.88/1.60	1955–60 intake manifold
538177	1961–62	389	62	D-Port	1.88/1.60	1961–64 intake manifold
543797	1963	389	62	D-Port	1.88/1.60
9770716	1963–64	421 HO · 64 GTO	68–72	D-Port	1.92/1.66	cc varies by source ▲
9771980	1963	421 SD	64	D-Port	2.02/1.76	Super Duty · tuliped valves
77	1965	389 GTO · 421 HO	68	D-Port	1.92/1.66	Intake bolt pattern shared on ALL 1965–79 heads
093	1966	389 GTO	68	D-Port	1.92/1.66	Last year of the 389

Big-Valve Era · 1967–1972

2.11/1.77 valves on the big 400/428/455 heads; 350 heads stay 1.96/1.66.

Code	Year	Application	Chamber cc	Port	Valves int/exh	Notes
670	1967	400 / 428 GTO·GP·FB	72	D-Port	2.11/1.77	14° valve angle introduced
97	late 1967	Ram Air GTO	72	D-Port	2.11/1.77	cc corrected 65→72 ▲
37	early 1968	Ram Air GTO	72	D-Port	2.11/1.77
96	late 1968	Ram Air GTO	72	ROUND	2.11/1.77	Round-port (distinct from the 1971 “96”)
62	1968–69	GTO auto trans	75	D-Port	2.11/1.77	Auto heads run a few cc larger
16	1968–69	GTO manual · 400/428	72	D-Port	2.11/1.77	“16” is reused on the 73–74 SD — see below
17	1968	350 Tempest	72	D-Port	1.96/1.66
18	1968	350 HO	68	D-Port	1.96/1.66
47	1968–69	350 auto trans	72	D-Port	1.96/1.66
48	1969	400 Ram Air III	68	D-Port	2.11/1.77	big-valve RA III — “350 HO” pairing unverified ▲
722	1969	Ram Air IV 400 GTO·FB	71	ROUND	2.11/1.77	Tall round intake port · tuliped
12	1970	400 Ram Air III GTO·FB	72	D-Port	2.11/1.77
13	1970	400 GTO·GP	72	D-Port	2.11/1.77
614	1970	Ram Air IV 400 GTO·FB	71	ROUND	2.11/1.77	Tall round intake port · tuliped
64	1970	455 GTO·GP	87	D-Port	2.11/1.77
96	1971	400 GTO·GP	96	D-Port	2.11/1.77
66	1971	455 all 4-bbl	114+	D-Port	2.11/1.77	Large open chamber (low compression)
197	1971	455 HO	108–111	ROUND	2.11/1.77	Round-port · tall intake · full # ends …797
94	1971	350 all	89	D-Port	1.96/1.66
7K3	1972	400 all 4-bbl	96	D-Port	2.11/1.77	Large exhaust crossover begins (72–79)
7M5	1972	455	114	D-Port	2.11/1.77
7F6	1972	455 HO	108–111	ROUND	2.11/1.77	Round-port · tall intake (“nailhead”)
7H1	1972	350	89	D-Port	1.96/1.77	Odd valve combo — verify ▲

Late D-Port · 1973–1979

Exhaust valve reduced to 1.66 in 1973 on the big-valve D-port heads.

Code	Year	Application	Chamber cc	Port	Valves int/exh	Notes
46	1973–74	350	89	D-Port	1.96/1.66
4X / 4C	1973–74	400 & 455 all (4C also 350 AIR)	96–111	D-Port	2.11/1.66	350 variants are 1.96/1.66
16	1973–74	455 SD 290 hp	108	ROUND	2.11/1.77	Super Duty · round, tall/wide port · SD keeps 1.77
6X	1975–79	350 & 400 all · 75–76 455	see sub-ID	D-Port	2.11/1.66	cc set by stamped sub-ID — table below
5C / 5X / 5G / 5I	1975–76	455 · some 350	93–114+	D-Port	2.11/1.66

Race / Rare

Tunnel-port race castings — not street heads.

Code	Year	Application	Chamber cc	Port	Valves int/exh	Notes
44	1969–70	Ram Air V Tunnel-Port 400 (race)	—	4-PORT	2.19/1.77	Race-only · tuliped 3/8" width · also 303 RA V (1969)

Aftermarket Aluminum

Modern replacement heads — offered in D-port and round-port, two chamber sizes each.

Code	Year	Application	Chamber cc	Port	Valves int/exh	Notes
D-Port	—	Aftermarket aluminum (Edelbrock Performer RPM & similar)	72 / 87	D-Port	2.11/1.66	1.77 exhaust optional
Round-Port	—	Aftermarket aluminum round-port	72 / 87	ROUND	2.11/1.66	1.77 exhaust & 2.19 intake optional

▲ Verification notes. 9770716: sources split 68 vs 72 cc. #97: chamber corrected from 65 to 72 cc (Wallace/PontiacPower consensus). #48: the 1969 400 Ram Air III big-valve head; the legacy “350 HO” pairing doesn’t match (the 350 HO uses small 1.96/1.66 valves) — confirm before relying on it. #7H1: the 1.96/1.77 350 combo is reported but unusual — verify on the physical head. Chamber cc’s are factory-reported and vary with production and milling. Abbreviations: HO=High Output, SD=Super Duty, RA=Ram Air, GP=Grand Prix, FB=Firebird, W72=400 4-bbl high-output (T/A 6.6).

Decoding the 1975–79 6X

6X Stamped Sub-ID Chambers

The 6X casting was used across several engines and chamber sizes. From 1973 on, Pontiac stamped a 1/4" tall sub-ID on the pad by the valve cover — that number is what tells the chambers apart.

Year	Engine	Valves	Casting	Stamped Sub-ID	Chamber cc
1975–76	400	2.11/1.66	6X	8	100.04
1975–76	455	2.11/1.66	6X	6	124.51
1977	350	2.11/1.66	6X	4	93.74
1977	400 / W72	2.11/1.66	6X	4	93.74
1977	400	2.11/1.66	6X	8	100.04
1978	400	2.11/1.66	6X	8	100.04
1978–79	400 / W72	2.11/1.66	6X	4	93.74

Don’t Get Caught

Port Type & Crossover Fitment

D-Port vs Round-Port flanges

Round-port heads (Ram Air IV, 455 HO, 455 SD) use a completely different exhaust flange than the common D-port heads. A D-port header or manifold will not seal on a round-port head, and vice-versa. Confirm the port shape before ordering headers or gaskets.

Exhaust crossover split (65–71 vs 72–79)

1965–71 heads and 1972–79 heads use a different exhaust-crossover passage — the 72-and-later heads have the large crossover opening. This changes which intake gasket and manifold fit. Match the crossover era when you mix heads and intakes.

Intake bolt pattern

Good news: the intake-manifold bolt pattern is shared across all 1965–79 Pontiac heads, so most intakes interchange on that dimension — but still match port type and crossover era.

Head Code Location on Pontiac Heads

Click image to enlarge — code is on the machined pad by the valve cover.

Got a head code you can’t place?

Send us the casting code and the stamped sub-ID (a photo of the pad works), and our techs will confirm the year, chamber cc, port type, and valve sizes — and what intake, cam, and headers match.

Ask a Tech »(866) 762-7527

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Valve sizes, chamber volumes, and port types cross-checked against Wallace Racing flow-bench data, PontiacPower head codes, and Butler Performance build experience. Chamber cc figures are factory-reported and vary with production and machining. Pontiac reused head codes across years and applications — confirm port type and crossover era before ordering intakes, headers, or gaskets. When in doubt, send us the code.

PONTIAC HEAD CHART
CASTING NUMBER	YEAR & FACTORY APPLICATION	CHAMBER VOL# CC'S	EXHAUST PORT	NOTEWORTHY ATTRIBUTES
528511	1958 370	62	D-Port	1.88/1.6 55-60 INT MAN
538177	61-62 389	62	D-Port	1.88/1.6 61-64 INT MAN
543797	63 389	62	D-Port	1.88/1.60
9770716	63 421 HO,64 GTO	65	D-Port	1.92/1.66
9771980	63 421 SD	64	D-Port	2.02/1.76
77	65 GTO, 65 421 HO	65	D-Port	INTAKE MANIFOLD BOLT PATTERN IS THE SAME FOR ALL 65-79 HEADS.
093	66 389 GTO	65	D-Port
670	67 400 GTO	72	D-Port
97	LATE 67 RA GTO	65	D-Port	ALL 67 & UP HEADS HAVE 2.11/1.77 VALVES UNLESS OTHERWISE NOTED
37	EARLY 68 RA GTO	72	D-Port
96	LATE 68 RA GTO	72	ROUND
62	68 & 69 GTO AUTO TRANS	75	D-Port
16	68 GTO MANUAL TRANS	72	D-Port
17	68 350 TEMPEST	72	D-Port	1.96/1.66
18	68 350 HO	68	D-Port	1.96/1.66
47	68 & 69 350 AUTO TRANS	72	D-Port	1.96/1.66
48	69 RA3 400, 350 HO	68	D-Port
722	69 RA4 GTO FBIRD	72	ROUND	TALL INTAKE PORT
12	70 400 RA GTO FBIRD	72	D-Port
13	70 400 GTO GP	72	D-Port
614	70 RA4 GTO FBIRD	72	ROUND	TALL INTAKE PORT
64	70 455 HO GTO GP	87	D-Port
96	71 400 GTO GP	96	D-Port
66	71 455 ALL 4BBL	114+	D-Port
191(797)	71 455 HO	108-111	ROUND	TALL INTAKE PORT
94	71 350 ALL	89	D-Port	1.96/1.66
7K3	72 400 ALL 4BBL	96	D-Port	LARGE EXHAUST CROSSOVER OPENING ON 72-79
7M5	72 455	114	D-Port	LARGE EXHAUST CROSSOVER OPENING ON 72-79
7F6	72 455 HO	108-11	ROUND	TALL INTAKE PORT
7H1	72 350	89	D-Port	1.96/1.77(ODD)
46	73, 74 350	89	D-Port	1.96/1.66
4X,4C	73, 74 400 ALL	96-111	D-Port	2.11/1.66
16	73, 74 455 SD	108	ROUND	TALL/WIDE INT PORT
6X	75-79 350 & 400 ALL 75-76 455	see chart below	D-Port	2.11/1.66
5C,5X,5G	75-76 455, SOME 350	93-114+	D-Port	2.11/1.66
EDELBROCK	PERFORMER RPM ALUMINUM	72 or 87	ROUNDPORT FLANGE	2.11/1.66 (1.77 optional)

HEAD C.C.'S ARE APPROXIMATE DUE TO PRODUCTION VARIANCES

OTHER SPECIAL CASTING INFORMATION

YEAR OF APPLICATION	ENGINE CU. IN.	VALVE SIZES	CASTING NUMBER	ADDITIONAL STAMPING I.D. NUMBER	CHAMBER VOLUME CC'S
1975-76	400	2.11/1.66	6X	8	100.04
1975-76	455	2.11/1.66	6X	6	124.51
1977	350	2.11/1.66	6X	4	93.74
1977	400/W72	2.11/1.66	6X	4	93.74
1977	400	2.11/1.66	6X	8	100.04
1978	400	2.11/1.66	6X	8	100.04
1978-1979	400/W72	2.11/1.66	6X	4	93.74

HEAD STAMP LOCATION ON PONTIAC HEADS

CLICK IMAGE FOR LARGER VIEW

There are many questions regarding the types of Edelbrock Aluminum Pontiac Heads. They can be quite confusing. Here at Butler Performance we try and give you the knowledge to distinguish the head types and assist you in selecting the correct head for your application.

The first question is the ability to distinguish between the two types of heads. Below is a picture of the Edelbrock Round Port and D-port heads side by side. One would notice that the round port actually looks like a sideways "D" that is pointing upwards. This is not a "D-Port" head but a round port instead. The d-port head looks like a set of "D"'s mirroring each other, in other words back to back. The round port heads take a round header flange.

Click Here for the Edelbrock Aluminum Head Installation Sheet