Part 2: Classic Cubes from a Modern LS1

...Ferrea valves, springs, and titanium retainers are then installed.The Ferrea double springs (with dampers) have a seat pressure of 175pounds and an open pressure of 375 pounds at an installed height of1.800 inches, as compared to the LS6 rates of 90 and 260 pounds. Sincethe MTI 455 H.O. continues generating tremendous power over 6,000 rpm,only a superior combination will ensure happy revving in the upperportion of the powerband with no valve float.

Rounding out the valvetrain is a set of Jesel 1.7:1 SS (SportsmanSeries) roller rocker arms, which replace the LS1/LS6 cast steel 1.7:1roller rockers. SS rockers are made with 2024 alloy bodies and featurebillet-steel stands. They are designed for stock-length pushrods. MTIsets up the engine to allow use of stock length (7.400 inches) pushrods,but upgrades to its own chrome-moly construction pushrods for increasedvalvetrain stability.

Here is the finished Stage III-R head. After a thorough cleaning of itsmounting surfaces with a quality grease and wax remover...

...the deck of the block is cleaned in a similar fashion and the ARPhead studs are installed. Gen-III engines use roller lifter trays thatare dropped in place before laying down the head gasket.

Here's a close-up of the backside of the roller lifter tray. Itsfunction is to positively locate the lifter, ensuring the roller staysin contact with the camshaft. MTI uses Comp Cams roller lifters toactuate the valvetrain.

Our Stage III-R cylinder heads are fitted to the 455 with Cometic MLSgaskets, which offer the proper 4.160-inch bore opening and a compressedthickness of 0.052 inch. The ARP head stud nuts are torqued down to 70ft-lb in the factory-recommended pattern, ensuring the increasedcylinder pressure of our MTI 455 H.O. monster won't induce a blown headgasket.

The engine is rotated and an MTI-ported GM oil pump and pick up areinstalled, followed by the stock GTO oil pan. Careful attention is paidto ensure the extra clearance required for the Rollmaster timing chainis accounted for. MTI uses genuine GM oil pan gaskets, and torques thepan bolts to 125 in-lb.

MTI tops off this powerhouse with either the stock LS6 intake or thisoptional FAST LSX intake, which is torqued to 50 in-lb. The FAST"composite," three-piece modular intake fits in the stock location andis designed to accept all factory hardware, fuel lines, and linkages.Since it is available with either a 78mm or a 90mm throttle body mount,MTI opts for the 90mm version and combines it...

...with its optional 90mm polished, billet-aluminum, high-flow throttle-body. When complemented with the FAST intake and MTI's own 90mm mass airflow sensor, this combination flows well over 1,000 cfm and adds 25-30 hp, according to MTI. An LS1 Speed high-flow induction system helps get the air in, and delivering the fuel is the stock pump at 43 psi and the stock rails. But the 28-lb/hr injectors have been swapped for Bosch 30-lb/hr units. MSD wires augment the stock ignition system, and 13/4-inch primary diameter Stainless Works long-tube headers evacuate the exhaust through a pair of 3-inch high-flow cats and a dual after-cat system. Throw on the optional underdrive crank pulley and those beautiful custom MTI 455 H.O. rocker covers, and this GTO is ready for action.