Car Craft
Click here to find out more!

LS Engine Build - The Garage-Built LS Stroker, Part II

Last Month's Homebuilt 404ci LS Engine Is Now Making Noise Testing Four Different Cylinder Heads On The Garage-Built LS Stroker, Part II

By , Photography by

Big Ports, More Flow
For years, we've been talking about the potential advantages of smaller intake ports that enhance intake velocity in an effort to make great torque for street engines. However, with the LS series of engines, these L92 and LS3 heads with their larger, rectangle-shaped intake ports seem to take exception to that concept when used on large displacement engines. If we had really looked at our own flow testing during development, we would have noticed that the CNC-ported cathedral heads offered a much better exhaust-to-intake-flow (E/I) relationship than the L92 heads. Looking at the E/I for the ported L92 heads reveals that the flow relationship indicates a need for more exhaust duration to help top end power. When we get to the actual dyno results, the lack of good exhaust port flow could be used to explain why the engine didn't quite make the power we thought it should.

Flow Data
Valve Lift Stock 6.0L Ported 6.0L E/I Percent
(Exhaust-To-
Intake Ratio)
Intake Exhaust Intake Exhaust
0.100 76 57 70 59 84
0.200 145 115 145 119 82
0.300 200 152 210 174 82
0.400 236 173 250 213 85
0.500 252 188 288 228 79
0.575 260 194 303 230 76
0.600 263 198 294 231 78

The stock 6.0L and WCRCH-ported versions come with a 70cc chamber and 2.00/1.55-inch valves. These flow numbers came from West Coast Racing Cylinder Heads and were tested on a 4.030-inch bore at a test depression of 28 inches.

Valve Lift Stock L92 GMPP Ported L92 E/I Percent
(Exhaust-To-
Intake Ratio)
Intake Exhaust Intake Exhaust
0.100 72 59 72 55 76
0.200 148 116 144 116 80
0.300 212 161 214 157 73
0.400 264 187 267 192 72
0.500 302 203 300 214 71
0.600 322 208 326 224 69
0.700 316 212 337 231 68

The GMPP CNC-ported heads come with a 70cc combustion chamber and stock 2.165/1.590-inch valves. Both sets of L92 heads were tested on JGM's SuperFlow 600 flow bench with a 4.060-inch bore adapter at 28 inches. Intake port volume on the CNC versions is 279 cc.

Cam Specs
Camshaft Duration (Advertised) Duration (At 0.050) Lift (Inches) Lobe Separation
XER281HR, intake 281 232 0.595 112
54-428-11, exhaust 283 234 0.598
LS1 277 LRHR, intake 276 227 0.614 113
54-458-11, exhaust 284 235 0.621

Valve lift numbers are based on the stock LS 1.7:1 rocker ratio.

Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!
0 comments
Car Craft