LS1 Refurbish - 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 installed 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 aftermarket heads and an intake on this bad boy as well as upgraded some of the other stock parts still holding us back, 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 Bullet

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 Affair

Mike said his porting generally adds about 25-40cfm to the exhaust runner, and 25-30cfm on the intake, given past experience, which will 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."

Curtain Call

With the motor properly broken in and ready to clear its throat, the time now came to see what kind of power the new bullet could make, and see what other hidden ponies lie within the PCM. It was then that we ran into problem number one, which put us behind schedule just a bit. On the first dyno pull, the car put out 346-rear wheel horsepower, but the dyno graph was skewed in areas, indicating slippage. On the second go around, we found out exactly what was slipping when we saw flames coming from the bellhousing at 5,800rpm or so. Suffice to say the Textralia clutch in our black Z28 Camaro, true to New Jersey form, went down in a blaze of glory. We replaced the burnt up clutch with a stock GM LS7 clutch, and after another 500 miles to break the clutch in, we were finally ready for the tale of the rollers.

The car was consistent, as the first pull kicked out 342-rear wheel horsepower and 314 lb-ft of torque. We knew that the car had a lot left in it when Matt looked at the information the dyno gave us. "The air/fuel ratio was rich, at around 12.4 or so, and it had 20 degrees of timing up top," he said. "The main reason why the power number was so low was the lean condition caused a small detonation knock at tip-in and the computer pulled all the timing out."

With that in mind, Matt got to work, doing his magic to try and get the tune to where it would be a tad bit richer, especially on tip-in, as well as giving the car more timing upstairs. "According to Mike, these heads really don't benefit from much more than 23 degrees of timing, so that is what I am going for, along with an air/fuel ratio of 12.8:1. I also have a few tricks up my sleeve to rid the engine of the knock at tip-in." When Matt was done, we gave it another try, and were rewarded with the results. The final numbers came in at 353-rwhp and 328 lb-ft of torque.

"At 6,000rpm, the car ran out of injector, and after that, they wouldn't support the engine going any higher," Matt said. "You can get bigger injectors to go past that limit, but for this combination, they will work just fine. The tune isn't a ragged-edge, glory number type of tune. It's something that just about everyone with this combination will see great power and drivability with, as well as being safe."

Though our low oil pressure prevented a proper baseline dyno test, Matt said, "In my experience and what I have seen come through here, though, a combination like this before the engine was rebuilt, with a tune, headers, and a cat-back exhaust, checks in around 305 horsepower on our dyno." That puts our guesstimate at around a 50-rwhp gain, with plenty more room to grow via the injectors and intake manifold (even an LS6 would be a substantial improvement). Not bad given our starting point and the money involved.

Those of you looking to replicate this build at home and capable of assembling an engine, expect to pay about $2,250 in block machine work and new parts. Hopefully Uncle Sam is kind enough to fork out that kind of cash come tax season. Unfortunately for those of you, like us, more apt to let the professionals at MCP do all the work, you will need at least another $1,000 for assembly. In retrospect, an LS6 intake manifold or injectors may have been a better investment than porting the heads, which as the result brought our total to a touch over $4,500. But we now have the foundation for a wicked heads/cam LS1 that should hopefully serve us well for years to come, and rival some of those 400+rwhp numbers we see in all the magazines with a few more dollars. Hmmm-maybe we'll wait for this year's refund check and see what more we can squeeze out of the tax refund rebuild. Now if only our accountant would crunch those numbers!