Part 2: Classic Cubes from a Modern LS1

The old valve seats are cut out using a Kwik-Way seat and guide machine.New seat pockets are then cut on the same machine and measure 2.131inches for the intake and 1.694 inches on the exhaust. The new MartinWells nickel chrome seats are pressed in and then attention turns to thevalveguides.

New Ferrea bronze valveguides are installed after the old cast-ironvalveguides are removed using an air hammer. The inside of the guidesare honed with a Sunnen guide hone and stones to achieve 0.0016 inchclearances on the intake and 0.0018 inch on the exhaust.

In order to support the larger valves and camshaft, upgrades to thevalvesprings were necessary. To accept the larger double springs, thestock spring seats have to be enlarged. MTI cuts out new seats to 1.435inches on the Kwik-Way machine to allow use of the larger Ferrea steelspring cup. The soft, stock aluminum cups are both insufficient indiameter and of the wrong material for a performance spring. With a seatpressure of 175 pounds, steel spring cups are required so the softaluminum isn't destroyed.

Beginning with a stock intake runner, note the casting boss at the roofof the port (bottom in photo) and the "cathedral" shape of the port.

MTI's Robert Maenza performs the rough-in porting with a carbide cutter,removing the casting boss and shaping the runner to the desired size toallow for superior flow and power.

Once the basic shape is complete, a flapper wheel with 36-grit paper,followed by 120-grit paper is utilized to polish out the port. On theexhaust, the same porting procedure is used. The completed intakerunners have outstanding flow, with the No. 1 intake checking in at336.2 cfm at 0.650 inch lift.

A three-angle valve job is performed on the Kwik-Way seat and guidemachine to correspond to the stock 45-degree seat angles on the Ferreastainless valves. Of course, a proprietary backcut is performed! Afterthe valve job, a lapping stick and red ink are used in conjunction withClover Leaf lapping compound to provide a good seal between the valveand seat surfaces.

As compared to the stock LS6 combustion chamber pictured earlier in thestory, this one has been extensively reworked. Note the smoothing of thespark plug boss at the bottom of the chamber and the contouring aroundthe valves.

MTI utilizes a SuperFlow SF600 flow bench with FlowCom hardware andsoftware to verify the heads have been ported to their requiredspecifications. Here you can see an intake runner has been set up fortesting. Once verified...