The fabrication wizards at Sled Alley have been busy on Mark Stielow’s latest 1969 Camaro project since our last installment. After installing the Detroit Speed Inc. front subframe, mini-tubs, and rear suspension, their attention turned to mocking up the powertrain system.
That included nestling the Chevrolet Performance LT4 crate engine into the Detroit Speed subframe with fabricated mounts, finding a solution for some of the drive accessories, accommodating the needs of a higher-capacity cooling system, and shoving a D&D Performance-supplied TREMEC Magnum six-speed transmission into a transmission tunnel that was originally designed for nothing larger than a Hydra-Matic automatic or a Muncie four-speed.
As it turns out, making room for the six-speed was a comparative snap next to the details surrounding the engine. That’s because the LT4, which was obtained from Scoggin-Dickey Parts Center, posed a number of installation challenges. Some, including fabricated engine mounts, were comparatively easy to overcome, while others such as accommodating air conditioning were more challenging.
The LT4 crate engine package doesn’t include an accessory drive system and there are two available for it from Chevrolet Performance: one for wet-sump applications and another for the dry-sump version. The A/C compressor included with the dry-sump drive kit ordered for Stielow’s car was unfortunately too large and the ports were clocked all wrong for a logical installation. Sled Alley overcame the challenge by notching the subframe to accommodate the placement of a more compact Sanden compressor from Vintage Air.
Along with us, Holley was looking over the shoulders while the Sled Alley guys did their thing with engine mounts and A/C system. In fact, Sled Alley and Holley collaborated on the mounts and we are told Holley will offer production LT-swap mounts shortly. Holley even helped produce a prototype mounting bracket for the Sanden compressor, which will also spawn another sorely needed swap component.
“Holley is very interested in supporting LS and LT engine swaps, which will ultimately make these engine installations a much easier endeavor,” said Mark Stielow. “It’s been great to work with them on this project.”
But while the A/C solution was achieved, everyone is still staring down at the engine and scratching their heads about the power steering—and more specifically, the lack thereof. Factory LT4 applications, which include the Corvette Z06, Camaro ZL1, and Cadillac CTS-V, feature electric power steering, meaning there isn’t a conventional power steering pump woven into the accessory drive system.
There’s no known aftermarket solution yet, either. It’s another challenge as the industry wraps its arms around the new LT engine family, but with 650 horsepower and 650 lb-ft of torque on tap from the supercharged LT4 crate engine, it’s a challenge worth accepting. We’ll be sure to detail the solution Sled Alley and Stielow work out for the power steering in an upcoming installment.
Cooling was another major powertrain-related project tackled for this installment. It involved opening up the original core support to increase the airflow to an enormous C&R Racing aluminum radiator, as well as the heat exchangers for the intercooling system and A/C system’s condenser.
Stay tuned as more of this landmark Pro Touring Camaro comes together in the next installment.
Oh, and there’s one more thing. In the last installment, we suggested Stielow name the car Envy, as a nod to its color and the emotion it will undoubtedly stir in enthusiasts and competitors alike. The suggestion was shot down when he officially named it Gunner.
We tip our hat. That’s not a bad name.
1. Obtained through Scoggin-Dickey Parts Center (SDPC), the Corvette Z06-based Chevrolet Performance LT4 crate engine carries a $13,755 list price on their website for the dry-sump version (PN 19332702) that Mark Stielow ordered. For roughly $500 less, there’s also a wet-sump version (PN 19332621). Considering its lofty 650hp/650-lb-ft output, it’s difficult to argue with the price, because you’d be hard-pressed to assemble a blower-ready long-block and add the supercharger, fuel system, etc., for any less. In fact, the SDPC price seems like a downright bargain.
2. The Gen V small-block LT engines are based on the familiar architecture of the LS-series engines, including the same 4.065-inch cylinder bores used in the LS3. The block casting also features provisions for GM’s cylinder deactivation system, different engine mounts, new knock sensors, and, as seen here, standard oil squirters. The only LS engines with factory oil squirters were the LSA and LS9.
3. The LT4 uses a pair of A356-T6 rotocast aluminum cylinder heads. The rotocast process turns the molding when the molten aluminum is poured, which helps create a denser casting that virtually eliminates porosity. Note the location of the fuel injectors mounted below the intake ports, as they spray directly into the combustion chambers. The ultra-high-pressure fuel pump, mounted at the rear of the valley cover, supports the extremely precise fuel control the direct injection system requires.
4. When it comes to moving air, conventional wisdom says the bigger the pump, the better. That’s not the case with the LT4’s supercharger. It uses an Eaton R1740 TVS 1.7-liter supercharger that is more compact and efficient than the 2.3-liter Eaton blower used on the C6 Corvette ZR1’s LS9 engine. The 1.7L’s rotors are shorter and smaller in diameter, enabling it to spin at up to 20,150 rpm—and get up to speed quicker. That’s about 5,000 rpm more than the LS9 blower, allowing more torque production at lower rpm and sustained boost at higher rpm. It also delivers comparable maximum boost: 9.4 psi vs. the LS9’s 9.7 psi.
5. The first challenge in mocking up the LT4 engine in the chassis was the engine mounts. The Detroit Speed front subframe was designed for LS-style mounts, but the LT mounting pattern doesn’t match. Sled Alley scratch-built steel mount adapters to marry the LT to the crossmember. We are told Holley is using the custom mounts as the template for production pieces they intend to release in the near future, making LT swaps that much easier.
6. The next issue with the engine installation was the air-conditioning compressor. Its low mounting position on the right-front corner of the engine made it essentially unusable with the Detroit Speed subframe. Besides its larger size, the inlet and outlet ports were aimed straight into the subframe, which wouldn’t work either. Sled Alley and Stielow would have to build an A/C system to replace the factory compressor, but it first required notching the subframe, which can be seen here below the alternator and next to the water pump pulley.
7. A Vintage Air-supplied Sanden SD-508 compressor is the foundation for the custom air-conditioning system and offers a number of advantages, the most important being its compact dimensions of approximately 8.4 inches long and 4.9 inches wide. It can also be clocked 90 degrees clockwise or counterclockwise to accommodate custom mounts such as with this project. It tucked nicely into the notched chassis.
8. A mounting bracket for the Sanden A/C compressor was required. While Sled Alley could have fabricated it, Holley stepped in to prototype one that they’ll likely offer soon as they expand their LT-swap components roster. They went high-tech with Stielow’s car, too, creating a rapid-prototype resin component for test-fitting.
9. The LT4 crate engine doesn’t include an accessory drive system, and there are two choices from Chevrolet Performance: a CTS-V-based kit for wet-sump applications and a Corvette-based system for dry-sump engines. This is the dry-sump version (PN 19332614), which includes the too-large A/C compressor that was ditched in favor of the more compact Sanden unit for this project, but neither the wet- or dry-sump drive kits include a power steering pump because the factory applications for the engine use electric power steering systems. There’s no adapter kit in the aftermarket yet, either, so there will be more fabrication for Stielow’s Camaro to include it.
10. With the engine and A/C system mocked in place, the cooling system was the next task to tackle. Its cooling capacity would have to be greatly improved to satisfy the supercharged LT4. While that would include a big, thick radiator, it would also require enlarging the opening in the core support for max airflow.
11. With years of experience, Stielow has learned that big blower engines in his track-capable cars are much happier and perform much better when running cooler, so he didn’t skimp for engine cooling with this aluminum radiator from C&R Racing. It is 28.5 inches wide, 21.3 inches tall, and 2.5 inches thick. It’s oversized even for the LT4, but Stielow plans to up the engine’s power output and this monster builds in the necessary headroom.
12. The stock opening in the core support is about 21 inches wide. To open it up to the cooling fin area of the new radiator, approximately 2 inches on each side of the opening would have to be cut away. Here, Sled Alley’s Matt Gurjack double-checks the measurements penciled in on the support before trimming the sheetmetal.
13. A pneumatic cutoff wheel did the trick for slicing the thin core support metal. Measure twice, cut once was the motto here.
14. The new radiator tucks in nicely within the widened core support opening, and a custom bracket can be seen in the lower corner to help secure it to the core support itself.
15. Sled Alley also fabricated upper mounting tabs for the radiator. The tabs will be welded to the core support and bolted to the radiator mounts to allow easy removal. And because the radiator, intercooler, and A/C condenser compose an assembly that has a fair amount of weight, it was mounted to the framerails with C6 Corvette isolators at the bottom. At the top are McMaster Carr 50-durometer rubber isolators. This setup allows the system to “float” without stress as it expands and contracts.
16. The front of the core support is getting crowded with heat exchangers for the air-conditioning system (the black condenser in front) and the supercharger’s intercooler (behind the condenser), making it all the more important for unimpeded airflow through the front of the car. At this stage, the components are mocked up to ensure fitment. They’ll be removed again before final assembly, so that the core support and complementing components can be painted.
17. When it comes to the cooling fan, Stielow, who is a General Motors engineer, opted for the 850-watt big boy from the Cadillac CTS-V, which is also powered by an LT4 engine. Besides its considerable airflow capability, Stielow selected it because it is pulse-width modulated (PWM), which offers greater temperature control and generally requires less energy overall. The rub with a PWM fan for this application is the crate engine controller’s fan control is a conventional low/high-speed system, so some calibration will be required to adapt the CTS-V fan’s system.
18. The fan was slipped behind the radiator to ensure adequate clearance between it and the accessory drive of the engine, and fortunately there were no clearance issues. The LT4 engine is a relatively compact assembly and even with the supercharger and its comparatively wide serpentine belt drive, there were no length or height problems to contend with. It will also fit beneath the stock Camaro hood with room to spare.
19. Here’s a look at the front of the engine compartment with the core support, radiator, cooling fan, and heat exchangers in place. The high-tech powertrain contrasts brilliantly with the as-found patina of the original Fathom Green exterior, which will be left alone on this track-focused Pro Tourer.
20. One more item under the hood: This master cylinder and booster from a C6 Corvette Z06 will support a four-wheel disc brake system. An adapter from Detroit Speed makes it a direct bolt-in, but the adapter itself will require a little fab work later on to close it off at the firewall.
21. Backing the LT4 engine is a TREMEC Magnum six-speed transmission from D&D Performance, which uses the stronger guts of the production-spec TR-6060 gearbox. This is a common swap that requires opening the transmission tunnel to accept the farther-back location of the TREMEC’s shifter. Also, the transmission is mounted a little higher in Stielow’s car, compared to other “standard” swaps, to achieve a 2-degree driveline angle and that required cutting out most of the tunnel to ensure adequate clearance around the “barrel” of the transmission.
22. Sled Alley fabricated a new tunnel after the final location of the transmission was determined. To accommodate the desired driveline angle, the front of the tunnel around the bellhousing area was raised about 1.5 inches and the sheetmetal will taper downward from there. The factory console won’t be used in the car, but Sled Alley’s Matt Gurjack believes it should still fit, as the tapered tunnel should still provide adequate clearance.
23. The finished tunnel looks like it was stamped at the factory with the rest of the floorpan. Note, too, the original-style ribs at the front of the tunnel. It’s a great detail for an aspect of the build that will be ultimately covered by Dynamat and carpeting. And with the custom driveline angle and mounting position for the transmission, a custom crossmember to support the transmission is required. It’s another swap component on which Sled Alley and Holley are collaborating.
Photography by Barry Kluczyk