With the economy being as it is, every dollar gets stretched to the limit and then some. In the case of the performance hobby, the more bang you get for your buck, the better. It costs money to go fast and make power, but what if good old Uncle Sam gave you enough to do it instead of trying to beg, borrow, steal, and suck up to your better half? Such is the case with our subject on the following pages. If this black '98 Z28 looks familiar, then you're not mistaken as this fourth-gen F-Body has graced the pages of GMHTP in the past. However, low oil pressure has forced the Camaro to not roam the streets as intended, but instead sit in the driveway waiting for some much-needed help. Enter our tax refund rebuild.
The 80,000-mile Z28 is no stranger to the chassis dyno, the famed Raceway Park quarter-mile, or anywhere in between. The last time the Z graced the pages of GMHTP we ditched the aftermarket SLP Loudmouth cat-back for a set of Dynatech SuperMAXX long-tube headers and a Corsa 3-inch exhaust. Throw in the SLP 160-degree thermostat, an SLP air lid along with a K&N filter, and a custom tune from East Side Performance, and the Z28 laid down 328 horsepower at the rear tires while pumping out 339 lb-ft of torque as measured on the shop's Dynojet chassis dyno. Not too bad for a stock LS1. After a while, though, high RPM gear changes took its tool on the all-aluminum bullet, and it was left stranded in the driveway. With low-oil pressure (15-20 psi at idle and/or cruising speed), the time had come to do the girl justice and rebuild the aluminum lung. In this day and age, though, rebuilding a fuel-injected LS1 can be a hefty task with an even heftier price tag. While we would have loved to throw some LS6 heads and intake on this bad boy, or some hot aftermarket heads, along with a bigger throttle body, mass air meter, and more, we decided to go another route, and that would be rebuild, refresh, and reinstall the motor with a small upgrade or two for as cheap as possible. We loaded the Camaro up in a race trailer and towed it down to Tune Time Performance in Toms River, New Jersey, where Matt Hauffe and crew were up to the task of refreshing our F-body. The plan was quite simple. Matt and the boys would be tasked with removing the LS1 and putting it in the capable hands of Mike Tiedemann at MCP Competition Engines, who had several tricks up his sleeve to make the most out of our '98 block and "806" heads. Once the motor was sealed up, it would be slung back into the Camaro where the engine would be broken in before being strapped to Tune Time's Mustang dyno for some tuning.
Wounded BulletThe one nagging question we had was why the engine started to lose oil pressure, without the death toll of a rod knock or the evidence of a spun bearing on either the crank main journal or the rod journal. "There really isn't an explanation for the engine to lose oil pressure other than it was getting tired and the clearances were a bit wide," Mike replied. "There wasn't anything wrong at all with either the main or rod bearings when I pulled it apart. The crank journals weren't scarred, so it was just a matter of catching it in time before something really bad happened." It is worth noting that the early '97-98 blocks do lack the open oil passage at the back of the block, which very well could have exacerbated the issue.
We felt safe in Mike's capable hands knowing that we should make considerably more power without giving up any streetability or durability. Step one was spec'ing a custom cam, ground by Comp Cams. The new cam is a single-pattern piece showcasing 228 degrees duration and .570-inch lift on both the intake and exhaust sides on a 116 LSA. "While this is what I would call a baby cam for the LS1, this cam profile will work great with the ported '806' heads and the stock LS1 intake manifold," Mike stated. "This should put the engine somewhere between 350 to 375 rear wheel horsepower, yet it will have great drivability, a broad torque curve, and a great powerband upstairs." Of course going with a lumpier cam meant upgrading the valvesprings as well, so we went just down the road to Manley to pick up a set of dual valve springs rated to .650-inch lift as well as locks, retainers, and seals. Manley also supplied a set of chromoly pushrods. "To be honest, we could have gotten away with single valve springs, as they wouldn't have run into any issues when it comes to coil bind, but I like the dual valve springs for two reasons," Mike explained. "First, having dual valve springs is an insurance policy in case one breaks as you don't hang a valve and create havoc. Second, when it comes to the LS motors, valvetrain stability is key, and for my liking, the dual valve springs add to the valvetrain stability."
Since there was little to no engine damage, most of the stock short-block was cleaned up and reused. "For the power level this engine will be at, the stock stuff will be sufficient," Mike says. "I just cleaned up the block, gave it a quick finish hone, and then cleaned up the pistons, rods, and crank. We are reusing the stock valves, so I cleaned them up as well." Meanwhile, new rings, bearings, lifters, and a timing set, as well as gaskets and bolts from Thunder Racing, were needed to complete the refresh. Wherever possible GM replacement parts were used, such as the oil pump. We had considered going with a high-volume unit, but Mike assured us that it was not necessary given our power level.
A Heady AffairWith this being a budget rebuild, a new set of heads were out of the question. After all, we needed to make sure we had enough coin to get the motor back into tip-top shape and the car running again. With that in mind, we turned our stock heads over to Mike, who proceeded to rework and refresh the factory "806" aluminum pieces. "There is a lot to be gained by a good porting job on these heads, especially the earlier '806' heads," Mike explained. "Most of the gains you will see with these cathedral-port heads in particular come on the exhaust side. I open up the exhaust ports and touch up the intake ports. For the most part though, all of the work I do is on the exhaust ports, as when I am done, they are completely different. I don't touch the chambers either because there really isn't much to be gained in that."
Mike's work speaks for itself, as the flow numbers for his ported heads are far superior to the stock numbers. "Stock, these heads will flow 200 to 215cfm or so on the exhaust side and between 265 and 268cfm on the intake," he said. "Now, with the porting work, the exhaust side improves to 240cfm and the intake to between 290 and 295cfm." The extra influx of air in and out, when combined with the camshaft, means the engine will breath better and make more horsepower over a wider power range. Of course those flow numbers are also owed to the attention Mike paid to the stock 2.00/1.95 valves and valve job. "I gave them a 45-degree valve job with a 30-degree back cut," Mike stated. "The 30-degree back cut will really help with the low-lift flow numbers." Last but not least, the heads were also cut to raise the compression ratio up a full point from the stock 10.1:1 to 11:1. "I milled the heads .025 to get the compression ratio up," Mike said. "I didn't have to deck the block, so for that small of an increase the slight shave I did on the heads worked. Even still, 11:1 will work on pump gas without a problem."