Ultimate Head Flow Charts


by Pete McCarthy and High Performance Pontiac 

1958 No. 528511 (1958 370-cid 270-hp 4-bbl)

Date cast: J277 Grade: 3 (3 cfm seat leakage)

Valve sizes: 1.88/1.60
Intake(S) Flow(cfm) Exhaust(S) Flow(cfm) Exh./Int
.100 46 .100 34 .74
.200 88 .200 61 .69
.300 119 .300 87 .73
.400 141 .400 98 .70
.500 148 .500 101 .68
.600 152 .600 102 .67 
1961-62 NO. 538177 (1961-62 195 & 389-cid)

Date cast: E152 Grade: 3 (3 to 6 cfm seat leakage)

Valve sizes: 1.88/1.60
Intake(D) Flow(cfm) Exhaust(S) Flow(cfm) Exh./Int.
.100 49 57 .100 39 .74
.200 95 95 .200 75 .79
.300 119 127 .300 104 .84
.400 125 130 .400 117 .92
.500 130 133 .500 125 .95
.600  130 133 .600 130 .99 
1963 No. 543797 (1963 389-cid 10.25:1 CR)

Date cast: A143         Grade: 1

Valve sizes: 1.88/1.60
Intake(D) Flow(cfm) Exhaust(S) Flow(cfm) Exh./Int.
.100 54 63 .100 39 .67
.200 103 105 .200 78 .75
.300 126 127 .300 104 .82
.400 130 129 .400 124 .96
.500 131 130 .500 134 1.02
.600 131 130 .600 139 1.07 
1963 No. 9771980 (1963 421 Super Duty)

Date cast: none Grade: 2 (2 cfm valve guide leakage)

Valve sizes: 2.02/1.76 (tuliped)
Intake(MP) Flow (cfm) Exhaust(MP) Flow (cfm) Exh./Int.
.100 61 63 58 62 .100 47 42 39 42 .70
.200 115 119 115 110 .200 77 75 72 74 .65
.300 147 147 151 149 .300 102 99 98 102 .68
.400 169 165 164 165 .400 120 121 120 122 .73
.500 178 173 174 178 .500 132 130 130 134 .75
.600 185 183 178 183 .600 138 137 139 139 .76
.700 188 183 180 184 .700 140 140 142 141 .77 
1963-64 No. 9770716 (1963 421 HO & 1964 421 HO/389 GTO)

Date cast: J304 Grade: 2 (3 cfm valve guide leakage)

Valve sizes: 1.92/1.66
Intake(S) Flow (cfm) Exhaust(S) Flow (cfm) Exh./Int.
.100 65 .100 33 .51
.200 115 .200 64 .56
.300 143 .300 86 .60
.400 149 .400 102 .68
.500 153 .500 110 .72
.600 155 .600 113 .73 
1965 No. 77 (1965 389 GTO & 421 HO)

Date cast: L124 Grade: 2 (3 cfm seat leakage)

Valve sizes: 1.92/1.66
Intake(S) Flow (cfm) Exhaust(S) Flow(cfm) Exh./Int.
.100 63 .100 35 .56
.200 1l1 .200 66 .59
.300 136 .300 85 .63
.400 142 .400 98 .69
.500 145 .500 106 .73
.600 149 .600 110 .74 
1966 No. 093 (1966 389 GTO & 421 HO)

Date cast: D136 Grade: 2 (worn guides)

Valve sizes: 1.92/1.66
Intake Flow (cfm) Exhaust(S) Flow (cfm) Exh./Int.
.100 59 .100 34 .58
.200 117 .200 67 .57
.300 139 .300 91 .65
.400 144 .400 100 .69
.500 147 .500 104 .71
.600 149 .600 108 .72 
1967 No. 670 (1967 400 & 428 large-valve--GTO, GP, FB 400)

Cast date: J156  Grade:1 

(Note: valve inclination angle decreased to 14° from 20°)

 Valve sizes: 2.11/1.77

Intake port volume (2 ports): 152.3 & 153 cc's
Intake(D) Flow (cfm) Exhaust(D) Flow (cfm) Exh./Int.
.100 73 75 .100 39 43 .55
.200 130 129 .200 76 79 .59
.300 148 150 .300 100 104 .68
.400 155 156 .400 117 117 .75
.500 161 160 .500 122 124 .77
.600 163 161 .600 129 128 .79 
1968-69 No. 16 (1968-69 400 & 428 large-valve D-port)

Date cast: A228 Grade: 2 (1 cfm seat leakage)

Valve sizes: 2.11 /1.77

Intake port volume (2 ports): 154 & 154.7 cc's.
Intake(D) Flow (cfm) Exhaust(S) Flow (cfm) Exh./Int.
.100 71 74 .100 46 .63
.200 126 122 .200 84 .68
.300 153 155 .300 106 .69
.400 158 158 .400 124 .78
.500 162 167 .500 132 .80
.600 165 167 .600 140 .84 
1969 NO. 48 (1969 400 "Ram Air III" D-port)

Date cast: K308                  Grade: 2 (worn guides)

Valve sizes: 2.11/1.77
Intake(D) Flow (cfm) Exhaust(S) Flow (cfm) Exh./Int.
.100 67 75 .100 38 .54
.200 116 119 .200 77 .66
.300 148 152 .300 103 .69
.400 156 159 .400 119 .76
.500 160 161 .500 128 .80
.600 165 166 .600 131 .79 
1969 NO. 722 (1969 Ram Air IV 400, round exhaust ports)

Date cast: none                      Grade: 1

Valve sizes: 2.11/1.77 (tuliped)

Intake port volume (2 ports): 182.6 & 183.6 cc's
Intake(MP) Flow (cfm) Exhaust(S) Flow (cfm) Exh./Int.
.100 63 71 62 70 .100 38 .57
.200 120 130 126 120 .200 79 .64
.300 156 172 164 158 .300 109 .67
.400 180 184 187 178 .400 131 .72
.500 194 193 195 190 .500 145 .75
.600 195 195 195 194 .600 151 .78
.700 197 195 197 194 .700 157 .80 
1969-70 NO. 44 (1969-70 Ram Air V Tunnel Port, 4-port exhaust)

Date cast: none Grade: 2 (1 cfm seat leakage)

Valve sizes: 2.19/1.77 (tuliped, 3/8-inch width)
Intake(S) Flow (cfm) Exhaust(S) Flow (cfm) Exh./Int.
.100 75 .100 37 .49
.200 129 .200 74 .57
.300 164 .300 100 .61
.400 196 .400 124 .63
.500 216 .500 140 .65
.600 233 .600 151 .65
.700 245 .700 159 .65
.800 253 .800 163 .64 
1970 No. 12 (1970 Ram Air III 400, D-port)

Date cast: H019 Grade: 1

Valve sizes; 2.11 /1.77
Intake(D) Flow (cfm) Exhaust(S) Flow (cfm) Exh./Int.
.100 73 71 .100 32 .44
.200 122 126 .200 75 .60
.300 151 151 .300 102 .68
.400 162 158 .400 115 .72
.500 164 162 .500 126 .77
.600 167 165 .600 132 .80 
1970 No. 64 (1970 455 GTO & 455 GP)

Date cast: I099 Grade: 2 (worn guides)

Valve sizes: 2.11 /1.77
Intake(S) Flow (cfm) Exhaust(S) Flow (cfm) Exh./Int.
.100 65 .100 38 .58
.200 111 .200 75 .79
.300 138 .300 98 .71
.400 148 .400 111 .75
.500 153 .500 120 .78
.600 156 .600 125 .82 
1970 No. 614 (1970 Ram Air IV & LS1 400, round exhaust port)

Date cast: none Grade: 1

Valve sizes: 2.11/1.77 (tuliped)
Intake(D) Flow (cfm) Exhaust(D) Flow (cfm) Exh./Int.
.100 71 76 .100 40 33 .50
.200 128 122 .200 85 76 .64
.300 172 169 .300 117 117 .69
.400 200 201 .400 139 128 .67
.500 201 203 .500 150 139 .72
.600 202 203 .600 157 147 .75
.700 202 203 .700 163 172 .83 
1971 No. 96 (1971 400-cid 8.2:1 CR;  96 cc D -port)

Date cast: G 030                        Grade: 1

Valve sizes: 2.11/1.77
Intake(D) Flow (cfm) Exhaust(D) Flow (cfm) Exh./Int.
.100 67 73 .100 33 38 .51
.200 115 122 .200 74 74 .62
.300 144 148 .300 99 96 .67
.400 160 160 .400 111 105 .68
.500 165 166 .500 118 112 .69
.600 169 170 .600 122 118 .71 
1971 No. 66 (1971 465 D-port low compression)

Date cast: D011 Grade: l

Valve sizes: 2.11/1.77

Intake port volume (2 ports): 145.2, 144.4 cc's

Exhaust port volume (1 port): 141.4
Intake(D) Flow (cfm) Exhaust(S) Flow (cfm) Exh./Int.
.100 72 70 .100 41 .58
.200 117 116 .200 83 .71
.300 149 148 .300 106 .71
.400 183 166 .400 117 .71
.500 171 174 .500 127 .74
.600 178 178 .600 132 .74
.700 181 180 .700 136 .75 
1971 No. 197 (1971 455 HO, round exhaust port)

Date cast: none Grade: 3 (5 cfm seat leakage)

Valve sizes: 2.11/1.77

Intake port volume (2 ports): 171.5 & 171 cc's
Intake(S) Flow (cfm) Exhaust Flow (cfm) Exh./Int.
.100 71 .100 39 .55
.200 122 .200 74 .61
.300 151 .300 96 .64
.400 167 .400 116 .69
.500 175 .500 125 .71
.600 177 .600 129 .73
.700 180 .700 132 .73 
1972 No. 7M5 (1972 250-hp 455-cid, 8.2:1 CR, 114 cc D-port)

Date cast: none Grade: 1

Value sizes: 2.11/1.77
Intake(D) Flow (cfm) Exhaust(S) Flow (cfm) Exh./Int.
.100 75 64 .100 37 .53
.200 115 114 .200 73 .64
.300 146 140 .300 93 .65
.400 161 160 .400 104 .65
.500 169 168 .500 111 .66
.600 175 171 .600 115 .66 
1972 No. 7F6 (1972 455 HO, round exhaust port)

Date cast: I167 Grade: 1 (NOS)

Valve sizes: 2.11/1.77 (flat-bottom, or "nailhead")
Intake(D) Flow (cfm) Exhaust(D) Flow (cfm) Exh./Int.
.100 71 72 .100 37 35 .50
.200 118 121 .200 78 75 .64
.300 152 157 .300 99 97 .63
.400 168 171 .400 114 107 .65
.500 172 172 .500 119 112 .67
.600 176 174 .600 120 115 .67
.700 181 177 .700 121 115 .66 
1973-74 No. 46 (1973 350 D-port)

Date cast: K132 Grade: 2 (worn guides)

Valve sizes: 1.96 (45° seat)/1.66

Intake port volume (2 ports): 152.4, 152.2
Intake(D) Flow (cfm) Exhaust(S) Flow (cfm) Exh./Int.
.100 54 63 .100 41 .70
.200 99 108 .200 81 .78
.300 145 150 .300 105 .71
.400 170 172 .400 118 .69
.500 181 181 .500 125 .69 
1973-74 NO. 4X (1973-74 400 & 455-cid D-port)

Date cast: J242 Grade: 2 (worn guides)

Valve sizes: 2.11 /1.66
Intake(D) Flow (cfm) Exhaust(D) Flow (cfm) Exh./Int.
.100 65 60 .100 32 35 .54
.200 108 110 .200 67 69 .62
.300 144 142 .300 89 87 .62
.400 163 160 .400 106 103 .65
.500 171 165 .500 111 113 .67
.600 172 175 .600 125 119 .70 
1973-74 NO. 4C (1973-74 350 & 400-cid Calif. A.I.R. D-port)

Date cast: K072 Grade: 1

Valve sizes: 2.11/1.66
Intake(S) Flow (cfm) Exhaust(D) Flow (cfm) Exh./Int.
.100 64 .100 33 34 .52
.200 109 .200 67 67 .61
.300 144 .300 86 91 .61
.400 160 .400 100 101 .63
.500 169 .500 107 109 .64
.600 172 .600 110 112 .65 
1973-74 No. 16 (1973-74 455 SD 290-hp, round exhaust port)

Date cast: K282

Grade: 1 (NOS), factory-installed 3-angle exhaust seat insert

Valve sizes: 2.11/1.77 (tuliped, 45° intake seat)
Intake(MP) Flow (cfm) Exhaust(D) Flow (cfm) Exh./Int.
.100 62 64 64 61 .100 45 43 .60
.200 112 121 116 109 .200 82 81 .71
.300 151 158 156 154 .300 108 109 .70
.400 169 171 173 172 .400 121 120 .70
.500 182 182 182 184 .500 127 125 .69
.600 188 190 190 191 .600 129 126 .67
.700 193 194 195 196 .700 130 127 .66 
1973-74 No. 16 (1973-74 455 SD 290-hp, round exhaust port)

Date cast: G143

Grade:1 (NOS), factory-installed 2 angle exhaust seat insert

Valve sizes: 2.11/1.77 (tuliped, 45° intake seat)
Intake(D) Flow (cfm) Exhaust(D) Flow (cfm) Exh./Int.
.100 52 63 .100 40 35 .65
.200 114 121 .200 80 79 .68
.300 154 160 .300 106 107 .68
.400 172 176 .400 117 122 .69
.500 184 189 .500 122 127 .67
.600 193 195 .600 124 129 .65
.700 198 202 .700 125 129 .64 
1975 No. 5C (1975 350/400/455-cid D-port)

Date cast: F184 Grade: 1

Valve sizes: 2.11/1.77
Intake(D) Flow(cfm) Exhaust(S) Flow (cfm) Exh./Int.
.100 63 63 .100 42 .67
.200 115 115 .200 78 .68
.300 143 146 .300 103 .71
.400 161 160 .400 118 .74
.500 164 165 .500 127 .77
.600 170 169 .600 131 .77 
1975-79 No. 6X (1975-76 400/455 & 1977-79 400 D-port)

Date cast: 0185 Grade: 2 (worn guides)

Valve sizes: 2.11/1.66

Intake volume (1 port): 154.0 cc's
Intake(S) Flow (cfm) Exhaust(S) Flow (cfm) Exh./Int.
.100 67 .100 51 .76
.200 112 .200 83 .74
.300 140 .300 96 .67
.400 158 .400 104 .66
.500 163 .500 110 .67
.600 167 .600 113 .68