Small Bore LS3

RLD Performance LS3 CNC cylinder head has more velocity, average flow and peak flow than a stock LS7 cylinder head.  This new casting is designed for engine sizes of 6.0L or bore size of 4" and larger.  However, we produce a small bore version of this cylinder head. This head utilizes a smaller intake valve to prevent cylinder bore impingement.  In stock form, this head could create the characteristic dip in the lower rpm area.  We have designed the correct camshaft to work with this combination.  The small bore LS3 may be an inexpensive solution to a high RPM small bore engine.  CNC versions of this head can add up to 20cc's to the intake port volume.  Poorly designed CNC ports can kill port velocity and should be utilized on engine sizes over 370 cubic inches.  Our Port design does not kill low lift flow.

We have found the L92 ports to not be sensitive to valve shape, valve cosmetics or brand.  So, a factory valve does flow as well as a Manley Race Master.  As Manley Race Master valves are approximately 23% heavier than a factory hollow stem valve, we do not advise using them.  The new Factory Hollow stem valve for the LS3 Corvette may be the best choice for weight and price point for a performance L92/LS3 head.  When making valve train determinations for the L92, valve weight is very important.

These heads are currently sold as new GM castings which are further CNC modified per the customers needs.  LS3/L92 heads can be modified in several ways.  Valve sizing can go up or down.  A smaller intake or exhaust valve would be more appropriate for engine sizes less than 6.2 Liters.  However, standard valve sizes can be utilized for engines of 6.0 liters and up.  Finally a LS7 large valve version is available for large bore combinations.   The combustion chambers can be CNC machined or left alone, depending on application.  We see no need to CNC the combustion chamber except for small bore applications.  It should be noted that in the stock form, we have found the L92 to have more average flow than the a stock LS7 under .600 lift.  Our CNG LL3 has more average flow than the stock LS7 and only 18 CFM shy of our highly modified LS7 head. 

For performance applications with this big valve head, we feel that a conical or beehive spring is inappropriate and should not be used.  We sell an ideal spring kit for these heads.  This head assembly can be built with premium hydraulic roller cam springs for increased lift and rpm range.

All airflow data is corrected data (Temperature and Atmospheric Pressure) at 28" of water.  Intake is measured with a shaped entry and the exhaust is measured with a stub pipe.  Polishing the runners add between 6-7 CFM at each lift point.

CombC =68-69                      68-69                                  68-69

RunnerCC = 277cc                  280cc                                  260cc

Valve =   2.16 1.59               2.16 1.59                             2.16 1.59

   RLD CNC LS3      VS     GM CNC LS3       VS          GM Stock LS3

Lift     I      E    E/I               I     E    E/I                            I     E    E/I  

.200  144  124  86%            150  105  70%                       151  111  74%

.300  224  179  80%            222  140  63%                       208  152  73%

.400  276  198  72%            260  168  65%                       256  174  68%

.500  313  223  71%            298  190  64%                       294  183  62%

.550  328  240  72%            NA   NA  NA                        NA   NA   NA

.600  338  248  73%            332  201  61%                       316  189  60%

.650  350  254  73%             NA NA

.700  347  255  73%             NA NA

AVG   290  215  74%          252  161  64%                      245  162  66%

Note - Max flow thru intake =322  M/E avg.=215  E/I avg. =69%

 RLD Performance, P.O. Box 890066, Temecula, CA 92589 (951) 676-4948, 9am-5pm Pacific Standard Time M-F,