Since the introduction of GM's famed L92 head it seems LS1 enthusiasts have been foaming at the mouth for a small-bore version that will accommodate the LS1/LS6's 3.89-inch cylinder. Unfortunately, the mammoth 2.165- and 1.59-inch valves simply won't fit, which meant a considerable redesign would be necessary. Enter Mast Motorsports. In the midst of developing a high-flowing 12-degree version of the popular L92/LS3 head that would significantly improve upon the square port's already impressive design, Mast decided it would like to cover all its bases with large- and small-bore versions (in addition to medium-bore). Mast's forward-thinking nature, you may remember, extends back several years when they jumped on the L92 bandwagon before anyone else knew how to spell variable valve timing. By 2009 Mast's core of freewheeling Texas A&M grads realized that it would be impossible to eke any more horsepower out of their VVT and other LS combos without a higher-flowing square port replacement for the stock heads.
Now some of you may be wondering whether a cathedral or rectangular port is better, and some of you may have already made up your minds, but officially the jury is still out. Both have excellent attributes and have each proven quite formidable on the dyno and at the track. Rather than debate what seems to be a futile and endless argument we chose to simply bolt down Mast's new heads and insert a matching cam into an otherwise stock LS1. Horace Mast, owner and engineer for MM, sent us a custom spec 226/240-duration roller to maximize the heads. Meanwhile, a GM L76 intake manifold, FAST 90mm throttle body, FAST injector adapters, and SLP throttle cable conversion bracket would replace the stock LS1 intake setup. Though this does add some cost to the overall install, consider the price of a high-flowing aftermarket intake manifold (that doesn't come with fuel rails, 42 lb/hr injectors, and an electronic throttle) and you will see that you are still coming out ahead (pardon the pun).
Race Krafter's President Bob...
Race Krafter's President Bob Wise has gotten some solid 11-second track times out of his 2001 Z28 using ARH headers, Corsa catback, NOS nitrous plate, SLP 85mm MAF, MTI lid, RPM-built 4L60E, Vigilante converter, and of course his own custom tune. But a man used to piloting much faster vehicles certainly would appreciate a good set of heads and a lumpy, yet streetable cam. Up until this moment the valve covers had never been off this LS1.
To test out this bad boy we went to none other than Race Krafters Automotive Machine in Lancaster, Pennsylvania. This little engine shop has quietly been building some very impressive late-model GM EFI motors in addition to its usual squadron of serious NHRA racers and the like. In fact, they often do work for the notorious Bill "Grumpy" Jenkins, including tune his 2004 GTO daily driver. RK President Bob Wise has piloted some very impressive single-digit race cars, but he takes great pride in his 2001 Z28 street car, which had previously been well into the 11s with little more than an NOS nitrous system, Corsa catback exhaust, airlid, RPM 4L60E trans, Vigilante converter, and a set of drag radials. A 9-inch rear with 3.73s and ARH long-tube headers have also found their way onto his Camaro lately, so it was ripe for a set of high-flowing heads and a lumpy cam.
| INCH LIFT |
INTAKE FLOW (CFM) |
EXHAUST FLOW (CFM) |
| 0.100 |
69 |
105 |
| 0.200 |
37 |
154 |
| 0.300 |
208 |
198 |
| 0.400 |
266 |
217 |
| 0.500 |
306 |
222 |
| 0.600 |
335 |
226 |
| 0.650 |
345 |
229 |
| 0.700 |
351 |
234 |
| 0.750 |
335 |
238 |
Scott and Craig got to work...
Scott and Craig got to work on pulling apart the Z28 to make way for the new heads, cam, and intake. The radiator was drained then removed from the shroud and electric fans.
The intake manifold was removed...
The intake manifold was removed in one piece with the throttle body and fuel rails attached. Of course, the rails must first be unplugged from the lines and the injectors must be unplugged from the harness.
The factory water pump is...
The factory water pump is removed along with the valve covers.
Off came the balancer and...
Off came the balancer and timing cover ... then we are just about ready for the cam swap.
To remove the passenger side...
To remove the passenger side head, the power steering pump must come off using the appropriate removal tool.
With the rocker arms and pushrods...
With the rocker arms and pushrods removed, the heads can be unbolted and liberated from the 5.7L block.
*Measured on Race Krafter's SuperFlow SF-1020 with 28 inches of water.