Texas Speed LS1 Cylinder Head Upgrade - Big Power, Small Change - Part 1

Before the heads can be unbolted, the main drive belt is removed by putting a 15mm wrench on the drive pulley and applying leverage until the belt has enough slack to take it off. The power steering pump is bolted to the driver-side head through a bracket and three 15mm bolts, two of which are accessible from the top side.

Once the plugs and wires have been removed, the six exhaust bolts that retain each Jet-Hot header to the cylinder head are unbolted with an 8mm swivel socket on an air ratchet. The headers are allowed to hang loosely in the engine bay and the T/A is lifted so that each header can be extracted through the bottom, after which the final power steering bolt is taken off and the car is lowered. The power steering pump is then shifted toward the driver-side fender and forward to facilitate installation of the PRC heads.

The coolant temperature sensor is disconnected and the sensor is removed from the front of the driver-side cylinder head with a 19mm wrench. Once complete, an air ratchet with a 10mm swivel socket is used to extricate the five top head bolts, while a 15mm swivel socket on an impact gun removes the five bolts in the middle and bottom of the heads. A total of 15 head bolts are used to provide the clamping force to seal the heads properly.

The cylinder head is removed from the driver side and the process is repeated on the passenger-side head.

On the bench, the valvesprings will be taken off using an LS-series in-car valvespring removal tool. A rag is placed under the valve in which the Comp 921 spring kit will be removed and a 1/2-inch ratchet with a 3/8-inch socket fitting is used to compress the spring until the valve locks and springs themselves can be taken out.

Wear inspection revealed that, since the Comp 921 spring kit had only a few hundred miles of use, it was in excellent shape. The Comp spring kit was then placed on the PRC heads and the spring assemblies were installed in the same manner in which they were removed.

Before installation of the heads can commence, some housekeeping is in order. A razor blade is used to scrape away the majority of head gasket material attached to the block, then a red Scotchbrite pad attached to a low-speed air die grinder is used to remove all the remaining gasket material. It's especially important to exercise extreme care to ensure that aluminum isn't scraped from the block surface. After wiping up residual coolant from the cylinders, the head sealing surfaces and cylinder bores (or tops of pistons) are sprayed with a grease and wax remover, then wiped down until spotless.

In order to reinstall the heads, a set of GM LS1 multi-layer steel head gaskets (PN 28-12498544, retail $48.99), along with new GM head bolts (PN 28-12498545, retail $47.99), are required, as LS-series head bolts are a torque-to-yield design and can't be reused. Since GM changed to a design that utilized all "short" head bolts for LS-series engines after May 2004, be sure to select the LS1 part number to ensure the correct combination of long and short head bolts.

Before installing the new heads, the coolant passage plug is transferred from the factory passenger-side head to the PRC head destined for the same side. Since the heads are interchangeable from side to side, it doesn't matter which head is chosen. The coolant temperature sensor was attached to the driver-side head once it was installed to prevent damage to the sensor.

Each head deck is wiped down with a grease and wax remover, and a final check of the block is made to ensure that it's clean and the locating pins on the heads are in place. The heads are then carefully placed onto the block and the replacement head bolts are slid into position. Head bolts 1-10, which are located in the center and the bottom of the head are first torqued to 22 lb-ft in a specific sequence that goes from the center outward, alternating sides. Once complete, a torque angle gauge (GM tool J 366660-A) is used to rotate the bolts 90 degrees. A second pass on bolts 1-8 puts an additional 90 degrees of rotation in, while bolts 9 and 10 (center head bolts, upper far right and far left) are rotated 50 degrees. Once complete, bolts 11-15 (the top row of bolts closest to the intake valley) are torqued to 22 lb-ft, alternating side to side, working outward.

Once both heads are installed, the Comp Hi-Tech pushrods are placed in the valve lifter sockets and the pedestal rail and rocker arms are reinstalled. A light coating of engine oil is placed on the rocker arms, then each rocker is torqued to 22 lb-ft. The valve rocker arm cover gasket is examined and replaced if it shows any signs of wear. In this case, the gasket was in good shape so the rocker cover will be installed and the four 8mm bolts torqued to 106 lb/in.

The car is lifted and the driver-side header is pushed up into position. A single bolt in the rear of the cylinder head is threaded in, holding it in place until the car can be lowered. The used factory GM manifold gasket is positioned and a single exhaust bolt is threaded into the front bolt hole. This rear bolt is then removed and the gasket is slid into position so the rear bolt can be threaded back in. The remaining four 10mm bolts are installed and snugged down, going from the center ports outward. This process is repeated on the passenger side and once both headers are snug, a torque wrench is used to put 20-25 lb-ft of torque on the bolts. The spark plugs are closely examined for signs of wear or detonation. After determining that the NGK TR-6 plugs were in "new" condition, they were checked for proper plug gap and reinstalled.

Once the headers are complete, the power steering pump is mounted on the driver-side cylinder head and the EGR pump, EGR tube, and both AIR tubes are mounted on the headers. The car is lifted, the remaining power steering bolt is secured, and the Y-pipe is installed. After a bit of struggling to get the lower bolt for the passenger-side AIR tube in place, Matt adjusted the fit of the Y-pipe and tightened it back down before reinstalling the driveshaft and torque arm. Stay tuned for testing in the next issue.