SBC Cylinder Head Info

The runners are the ports in the heads, one intake and one exhaust port for each cylinder. The intake runner connects the intake manifold to the intake valve and the exhaust runner connects the exhaust valve to the header or exhaust manifold.

There are many ways to compare cylinder heads when doing an engine build, but the two main ones are runner volume and CFM of air flow through the runner at a certain valve lift. This is done on a flow bench where air is pulled through the runners at a 28" depression of water. In other words, more and more vacuum is applied to the runner until there is enough vacuum to pull a 28" high column of water up into a tube (manometer). The volume of air that is passing through the runner is then measured and recorded. You would start with the valve off its seat at 0.100", then test again with the valve off its seat at 0.200" and so forth through the range of valve lift that you're testing.

Comparing heads by flow can get very confusing if you don't set some kind of mean figure to look at on each head. A generally accepted figure is 0.400" valve lift. Any cam you use will pass through 0.400" valve lift twice on a cycle, once when opening and once when closing, whereas if you use some higher figure, the cam you're going to use might not even open the valve that far, so the numbers are meaningless.

In choosing heads for a high performance street motor where rpm's will be limited to somewhere around 6K, I like to use the formula (CID X 0.5 = intake runner volume). For instance, on a 0.030"-overbored 350, cubic inch displacement = 355. So, (355 X 0.5 = 177.5) Now if you were building for torque and lower rpm's you might back that down to 170 for runner choice, depending on flow. If you were building for power through the entire range, you might step up to 180 cc runners, again, depending on the flow figures.

VOLUME VS FLOW. You'll see in the chart I've included that there are some heads with smaller runners that will outflow heads with larger runners. What that tells you is that the heads with the larger runners don't have the VELOCITY that the smaller runners do, so you can't base your choice purely on the runner volume. If the heads don't provide sufficient velocity, then they will not contribute to good cylinder filling while the valve is open. This is demonstrated with the GM 12558060 L31 Vortec heads for instance. The intake runner is only 170 cc's, but it flows 227 CFM @ 0.400" valve lift. Notice the head beside it in the chart, the GM Fast Burn. With a 210 cc intake runner it only flows another 5 CFM over the Vortec at 0.400" valve lift. That tells you that the VELOCITY in the Vortec is much higher at that point and it would make a much better street head on a 355. Of course, the Fast Burn is moving quite a bit more air at higher valve lifts and so would make more power in a bigger motor with a more aggressive cam or a smaller motor that will be revved much higher than 6K and will pass enough air to support the larger runners.

I'm just trying to get you to understand the relationships between heads and provide you with enough information to make an intelligent decision. We see builders all the time on here who think they are going to put together a world beater 355 by using 230 cc heads. Well, it just ain't gonna happen and now you know why. Bigger is not necessarily better in this case.



I've compiled the following information on SBC Cylinder heads to help compare them. For the flow remember bigger is not always best. Some of the heads with large flows and big runners are not going to be good street heads, since they will have slow flow through the runners at street rpm. Also if you have a cam with less than .500 inches of lift then the flows at .500 of an inch and above mean nothing to you. A lot of people recommend looking at the flows around .400 for a street motor as that is the lift you will see for a good part of the cam duration.

The flow figures below are from a couple different sources, so we are not necessarily comparing apples to apples, but they should be close.

A special thanks to members for helping me with some of the numbers below.


AFR 180cc -- AFR 190cc -- AFR Race 210cc -- AFR 205cc LS1 Mongoose Street Head -- AFR 205cc LS1 Mongoose Street Head -- AFR 180 Eliminators -- AFR 195 Eliminators

Brodix 8 Pro -- Brodix Track 1 -- Brodix IK180 -- Brodix IK200

Canfield Aluminum

Dart Conquest 200 -- Dart Iron Eagle 220

Edelbrock RPM -- Edelbrock 23 deg -- Edelbrock Victor Jr.

Edelbrock E-Tec 170 -- Edelbrock E-Tec 200 -- Edelbrock Performer

EngineQuest 50 cc 23 degree Heads

GM Fast Burn -- GM Vortec 855 -- GM Vortec Bow-Tie Small Port

GM Vortec Bow-Tie Large Port -- GM 882 -- GM 441 -- GM 462 -- GM LT1 372

GM L98 Vette -- GM LT4 -- GM LS1

Holley System Max

Patriot Performance

Pro Top Line (Lightning) 180's -- Pro Top Line (Lightning) 200's -- 200 Aluminum

Trick Flow 23 Deg. -- Trick Flow Twisted

World SR Torquers -- World Sportsman II



Manufacturer &

Head Type

Valve Sizes I/E AFR Street 180cc

Aluminum

2.02/1.60
AFR Street 190cc

Aluminum

2.02/1.60
AFR Race 210cc

Aluminum

2.08/1.60
Edelbrock RPM
.

.
Edelbrock

23 deg


Chamber Size 74cc & 68cc 74cc & 68cc 76cc 64cc & 70cc 71cc
Intake Runner 180cc 190cc & 195cc 210cc 170cc 212cc
Exhaust Runner 64cc 64cc 80cc 60cc 60cc
Flow Int/Exh @

See footnotes: *10 *10 *10 *4 *4
0.100 ?/? ?/? 72/61 78/69
0.200 129/108 129/108 135/112 134/105 140/116
0.300 195/156 195/156 197/145 188/140 200/158
0.400 240/178 240/178 245/185 224/160 242/195
0.500 255/190 260/190 273/205 233/172 270/213
0.600 260/194 262/194 282/215 233/179 275/224
0.700 285/220


Manufacturer &

Head Type

Valve Sizes Edelbrock
Victor Jr.

Edelbrock
E-Tec 170

Aluminum

1.94/1.50
Edelbrock
E-Tec 200

Aluminum

2.02/1.60
Edelbrock
Performer


Chamber Size 70cc 64cc 64cc 70cc
Intake Runner 215cc 170cc 200cc 170cc
Exhaust Runner 60cc 70cc 78cc 60cc
Flow Int/Exh @

See Footnotes: *1 *9 *9 *2
0.100 67/64 64/54 67/57 66/55
0.200 123/111 130/104 122/110 135/103
0.300 173/145 186/140 175/153 186/135
0.400 219/180 220/169 223/182 215/151
0.500 255/198 232/183 252/196 220/165
0.600 275/206 238/190 259/204 222/169
0.700 284/? 265/207


Manufacturer &

Head Type

Valve Size World Sportsman World SR Torquers

Iron

2.02/1.60 Dart Conquest 200

Dart Iron Eagle

Canfield



Aluminum
Chamber Size 64 & 72cc 67 & 76cc 64 & 72cc
Intake Runner 200cc 170cc 180 to 230cc
Exhaust Runner
Flow Int/Exh @

See Footnotes: *1 *3 and *6 *1 *1 *1
0.100 67/55
0.200 132/102 128/104 126/105 129/112 141/107
0.300 187/131 179/140 171/133 182/139 201/143
0.400 225/150 205/156 217/162 226/166 247/175
0.500 240/164 221/166 252/179 258/178 258/190
0.600 243/162 225/170 274/188 255/186 257/200
0.700 268/? ?/187


Manufacturer &

Head Type

Valve Size Brodix 8 Pro Brodix
Track 1
Holley System Max

Trick Flow
23 Deg.

Aluminum
Trick Flow
Twisted

Aluminum

Chamber Size 69cc 64cc 67
Intake Runner 215cc 190
Exhaust Runner 82
Flow Int/Exh @

See Footnotes: *1 *1 *1 *8 *1
0.100 60/50 51/58
0.200 125/94 130/103 130/92 136/98 127/116
0.300 177/123 178/142 184/122 191/136 186/155
0.400 220/144 223/166 222/148 230/163 227/183
0.500 254/164 256/175 242/172 253/177 254/204
0.600 226/170 259/183 252/187 254/190 265/213
0.700



Manufacturer &

Head Type

Valve Size GM Fast Burn

GM Vortec L31

PN# 12558060

Cast Iron

194.150
GM L98 Vette


194.150 ?/?
GM LT4

GM LS1


2.00/1.55

Chamber Size 62cc 64cc 58cc ? 65cc
Intake Runner 210cc 170cc 204cc
Exhaust Runner 78cc
Flow Int/Exh @

See Footnotes: *2 *6 and *7 *3 *1 *6
0.100 62/55 70/49 55/52 83/62
0.200 136/104 139/105 120/104 147/114 134/104
0.300 187/133 190/137 160/133 197/141 189/136
0.400 232/158 227/151 186/151 230/167 222/165
0.500 266/180 239/160 196/170 250/180 240/179
0.600 275/193 229/162 243/185 252/185
0.700


Manufacturer &

Head Type

Valve Size GM 882

Cast-Iron
GM 441

Cast-Iron

1.94/1.50
GM 462

Cast-Iron

1.94/1.50
GM
LT1 372


1.94/1.50

Chamber Size 76cc 76cc 62cc 56cc
Intake Runner 151cc 155cc 156cc 170cc
Exhaust Runner
Flow Int/Exh @ 28 in.

See Footnotes: *5 *6 *6 *6
0.100 70/58 55/45 50/54 72/53
0.200 125/108 110/83 119/91 129/101
0.300 175/135 160/118 167/121 180/136
0.400 204/141 194/133 198/134 213/155
0.500 205/142 201/146 212/139 214/165
0.600 206/142 203/148 218/142 215/171
0.700
Manufacturer &

Head Type

Valve Size Pro Top Line
Pro Lightning 180

Iron Heads (same
casting as Alum.)
2.02/1.60
Pro Top Line
Pro Lightning 200

Iron Heads

2.055/1.60
Pro Top Line
Pro Lightning 200

Alum. Heads

2.055/1.60
GM

Vortec Bow-Tie Small Port

PN# 25534421

Cast Iron

2.00/1.55 GM

Vortec Bow-Tie Large Port

PN# 25534431

Cast Iron

2.00/1.55
Chamber Size 50cc/64cc/72cc 50cc/64cc/72cc 50cc/64cc/72cc 65 cc 65cc
Intake Runner 180cc 200cc 200cc 175cc 206cc
Exhaust Runner 65cc 77cc
Flow Int/Exh @ 28 in.

See Footnotes: *12 ------- *13 *13 *13 *14 *14
0.100 58/49 -----74/57 69/57 71/57 67/? 63/?
0.200 113/93 -- 151/101 134/101 146/101 136/? 134/?
0.300 163/125 - 207/157 192/157 204/157 182/? 181/?
0.400 203/151 - 243/177 236/177 250/177 223/? 227/?
0.500 231/170 - 258/186 261/186 260/186 251/? 258/?
0.600 247/177 - 263/190 269/190 269/190 240/? 255/?
0.700 247/182 - 270/194 278/195 276/195 240/? 261/?
Manufacturer &

Head Type

Valve Size
Brodix IK180

Aluminum


2.02/1.60

Brodix IK200

Aluminum


2.02/1.60
AFR -- LS1 Mongoose Street Head


2.02/1.60
AFR -- LS1 Mongoose Strip Head


2.08/1.60
Chamber Size 64 cc or 70 cc 64 cc or 70 cc 66cc or 76cc 62cc or 72cc
Intake Runner 180cc 200 cc 205cc (same as stock) 225cc
Exhaust Runner ?? ?? ?? ??
Flow Int/Exh @ 28 in.

See Footnotes: *15 *15 *10 *10
0.100
0.200 138/112 123/100 140/112 150/120
0.300 188/149 181/145 200/170 220/178
0.400 234/167 230/164 251/203 266/220
0.500 243/175 253/171 281/221 304/241
0.600 245/178 261/176 298/230 320/250
0.700
Manufacturer &

Head Type

Valve Size AFR

180 Eliminators


2.02/1.60
AFR

195 Eliminators


2.055/1.60
AFR

195 Eliminators



2.055/1.60 Patriot Performance

Freedom Series SBC 23 Degree Heads

2.02/1.60
Enginequest

23 Degree Iron



2.02/1.60
Chamber Size 65 cc or 75 cc 65 cc or 75 cc 65 cc or 75 cc 64 cc 50 cc
Intake Runner 180cc 195 195 ?? 180cc
Exhaust Runner ?? 80 80 ?? ??
Flow Int/Exh @ 28 in.

See Footnotes: *16 *16 *17 *18 * 19
0.100 70.4/56.7 70/52 67/56
0.200 138/110 137/110 149.5/114.1 132/94 134/110
0.300 198/158 194/158 201.2/164.9 180/127 185/140
0.400 240/190 240/190 253.2/199.6 220/162 216/175
0.500 260/207 270/207 280.2/217.7 244/183 237/188
280/211 @ .550 277/222 @.600 250/190 @.550 244/190@.600
286/215 @ .600 276/225 @.700 260/195@.600



Footnotes:

*1 -- These flow numbers come from Chevy High Performance Magazine Data.

*2 -- These flow numbers come from Pace GM Parts.

*3 -- These flow numbers come from misc. sources.

*4 -- These flow numbers come from Edelbrock

*5 -- These flow numbers come from Car Craft - Jan 2001

*6 -- From Paul Shufelt

*7 -- From Chevy High Performance Feb. 2001

*8 -- From Trick Flow (Flow numbers)

*9 -- From Edelbrock's Site

*10 -- From Air Flow Research Site

*11 -- From Jim Scottt

*12 -- Chevy High Performance Feb. '04 -- Tested at Westech with SuperFlow 600 Flowbench @28-in H2O

*13 -- Pro Topline Ltd.'s Internet Site

*14 -- Super Chevy p. 39 December 2005

*15 -- Brodix Site FLOW CHART cfm @ 28" H2O

*16 -- Buy AFR Website

*17 -- Joe Sherman HOT ROD March 2007 p. 94

*18 -- Flow Figures taken on their Superflow 1020 Bench 4.060" Bore

*19 -- Popular Hot Rodding Oct. 2007 p. 92