Clean, good-running 402 and...
Clean, good-running 402 and Turbo 400 transmission were yanked in preparation for the LS6 swap.
In our last issue, we introduced the '70 LS6 Chevelle SS built by GM's Performance Division. What makes this particular LS6 Chevelle so interesting is that the engine is a new LS6 (PN 12562190)-the very powerplant that moves the Corvette Z06 with such gusto.
The folks at the Performance Division started with a genuine Chevelle SS 396. Besides dropping in the modern engine, GM's new 4L65E transmission (PN 24221888) was bolted in, too. With a higher torque capacity than the 4L60E transmissions found in countless Z28s, the 4L65E promises to hold up to the 405 horses and 400 ft-lbs of torque of the LS6.
For 2003, GM offers two crate versions of the LS6: one is the complete engine (minus electronics) listed above, while the other (PN 12498399) is a long-block assembly, but it comes with a Camaro-style oil pan. (The Corvette pan has "wings," making it harder to swap into most vehicles.)
The 4L65E was originally developed for use with the V-8-powered cars of GM's Holden subsidiary in Australia, but it's now available in the USA as an over-the-counter part available through GM dealerships' parts department.
Test-fitting the LS6 engine...
Test-fitting the LS6 engine included the use of plywood to mock the position of the motor mounts.
The remainder of the powertrain includes a custom aluminum driveshaft (shortened to fit the new transmission) and the Chevelle's stock (but refurbished) 12-bolt Posi-equipped rear axle. It's fitted with a '70-correct 3.31-ratio ring and pinion.
As for the rest of the car, it was in pretty good shape when purchased by GM, but required a thorough going-through to restore a like-new appearance. There are some neat details inside the car, too, including an Abbott Enterprises Cable X converter, which allows the use of the stock speedometer with the new, electronic transmission. The news trans was also complemented with a console shifter "PRNDL" cover from Year One that has a readout indicating the overdrive position of the transmission.
We covered the cosmetic restoration of the Rally Red Chevelle, including bodywork, chassis detailing and interior work, in the last issue of SUPER CHEVY. With this issue, we delve into the LS6/4L65E combo's installation.
Although the Chevelle's basic restoration was mostly cosmetic, it was a completely different story when it came to swapping the old iron big-block and Hydramatic for the aluminum LS6 and electronically controlled 4L65E.
"We started with the stock locating point of the engine and transmission," says Keith Benson, project manager. "From there, we mocked up where the engine and transmission would mount."
Installation of the engine...
Installation of the engine was made infinitely easier with the removal of the Chevelle's front "dog house." (Full-frame cars are a breeze to work on this way.)
Besides providing a logical starting point for the powertrain's placement, maintaining the original engine/transmission mating point allowed the shift linkage to be bolted up, albeit with a few necessary modifications. But knowing what other parts would be necessary for the swap wasn't so apparent. For that information, the technicians performing the swap consulting an excellent guidebook produced by General Motors: "LS1 Engine Kit Installation Guide" (GM PN 88959384).
"The book is a must for anybody who wants to build a car like this," says Mark McPhail, GM's powertrain manager for special vehicles. "The book lists all the available parts and part numbers, and recommends what should be used when swapping in an LS1-based engine."
We were impressed by the thoroughness of the book, which includes side-by-side comparisons of Corvette, Camaro and GM Truck LS1 varieties, including oil pans and front accessories. There are even recommendations for cooling fans. We suggest buying the book before you buy an engine, or start hacking up your car's chassis.
Close QuartersEven with the LS1 installation guide, snugging the LS6 into place took some planning and ingenuity. Here's what Benson and his crew did to make it fit:
 The LS6 engine used in the...  The LS6 engine used in the Chevelle is an '03 engine, rated at 405 hp. In this photo, the engine is wearing Camaro exhaust manifolds, but they'll be swapped for JBA headers. Also, the engine's front-mounted accessories come from an '02 Camaro, and the fuel rail on top of the engine has been reversed to mimic the fuel line routing of the '70 engine. |  To seat the engine properly...  To seat the engine properly in the A-body chassis, motor mounts were custom built. Currently, there is no aftermarket motor mount to attach an LS1-based engine to an early A-body frame. |  Another Camaro piece on the...  Another Camaro piece on the engine is the oil pan. But, even it wasn't a direct fit. The aluminum pan was carefully cut and notched to clear the Chevelle's front crossmember. A truck oil pan was tried, too, but it was deemed too deep. |