Memory is a funny thing-you always remember the good times, but the bad times just fade away. Take our favorite musclecars for instance. We have fond memories of tooling around back in the day, but we seem to forget how bad the fuel economy was without overdrive. And now that you've purchased the dream car of your youthful yearnings, you've discovered that vintage Powerglides and Turbo 350s have a very hard time living up to that multi-overdrive slush-o-matic in your luxurious Cadillac.
You've had it up to here with that antique trans, and you've decided to put a real overdrive in your A-body, the only problem is, it just won't fit. You're ready to break out the chopsaw and git-r-done, but where do you start? PHR is here to answer that, and we brought our friends from American Muscle Cars to show you how.
Here's the deal: Classic Industries boss Mark Vogt decided it was high time to finish his own dream car project. And knowing how popular GM A-bodies are with PHR readers, we decided to paint a big fat bull's-eye on Mark's '67 Pontiac Pontiac Tempest convertible, and bring the story to you. This would be no backyard slap-together, so Mark enlisted the artisans at American Muscle Cars (AMC for short) in San Bernardino, California. If that name sounds familiar, it's because it's the source for Dynacorn reproduction Camaro bodies that are all the rage. AMC got the nod to distribute these based on its vast experience in musclecar restoration and fabrication, and that's exactly why Mark chose AMC for his Pontiac project.
Like many PHR readers, Mark saw the need to update the Tempest to modern standards, which meant-among other things-swapping in a late-model LS2 and 4L60E overdrive trans from a 2005 GTO donor car. (See more photos of Mark's Tempest at www.backyardcars.com.) American Muscle Cars was then charged with the responsibility of blending the classic A-body design with modern mechanicals, including Air Ride Technologies suspension, and creating a work of art that would wow attendees at the upcoming SEMA show in Las Vegas. We also need to mention that the Tempest was dressed with a full line of GTO regalia from Original Parts Group-all in homage to the top-dog Poncho. Yeah, baby!
As you'll see, nothing is done halfway at AMC, and this trans tunnel massage had the book thrown at it. You'll do fine by using aftermarket motor mounts designed for the LS-to-A-body swap, and you can pass on the driveshaft tunnel work in most cases too. AMC also made the extra effort to fabricate the tunnel cross bracing that many home-builders leave out. This is perhaps the toughest part of the job, but in the case of a convertible with lots of power, Mark didn't want his dream car to start coming apart at the seams. At the end of the day, it was time and money well spent.
If it looks hard to do, that's because it is. But don't despair; it is a doable job by the well-traveled hobbyist. The thing to keep in mind is the AMC work shown here is a spare-no-expense job on a top show car that is getting the works. If you're just swapping out a trans on a driver, the job will be way easier.
So what's it like to make room for a real transmission? Do you have what it takes to git-r-done? Check out the pix for a look-see. Next month, we're going to show you the next work of art AMC performed on Mark's modern GTO-the custom console. Trust us, you ain't seen nothin' yet...
So You Wanna Try It Yourself?
Building your own custom trans tunnel is no easy job, but then PHR readers aren't run-of-the-mill car guys either. Besides your normal selection of hand tools and mechanical aptitude, you're going to need some specialty tools, serious fabricating chops, and a load of materials from your local metal supplier. To give you a head start, here's the list of stuff American Muscle Cars used. Keep in mind that the Tempest in this story had custom motor mounts for its LS2 donor engine. A-body LS-series motor mounts are available from the aftermarket, so you can avoid that job if you want. Also, our photo car had an Air Ride Technologies suspension, necessitating the expansion of the driveshaft tunnel for "laying frame." This operation could be skipped in a normal transplant.
*MIG welder (Miller 135 220-volt used)
*selection of ballpeen hammers
*oxyacetylene torch with rosebud tip
*die grinder with cut-off wheel
*18 gauge cold rolled steel (most of a 4 x 10 sheet used)
*1.5-inch diameter, .120-wall DOM round tubing (for trans crossmember)
*3/8-inch, 6061 T6 aluminum billet sheet/bar stock, 4.5 x 5.75-inch wide (motor mount adapters)
*3/16-inch sheet cold rolled steel (motor mounts)
*small-block Chevy motor mounts
*1/8-inch cold rolled steel (for tunnel support braces)
*non-corrugated cardboard sheets & masking tape (for model mock-ups)
*If the car is completely stripped, it takes one qualified person roughly two weeks.
Musclecars like Mark Vogt's...
Musclecars like Mark Vogt's '67 Tempest convertible are a blast from the past, but like many of us, Mark discovered that original non-overdrive transmissions and gas-guzzling engines are no fun on the highway. The solution Mark found was to transplant the engine and trans from a wrecked 2005 GTO donor car.
This is the object of Mark's...
This is the object of Mark's infatuation: an LS2 and 4L60E from a 2005 GTO. Somehow, the job was to get all this stuff to fit into a car built back in the Johnson administration.
When you strip away the carpet,...
When you strip away the carpet, seats and console, this is the room you've got to work with on a '67 Tempest. For the most part, this is the same for all Pontiac, Oldsmobile, Buick, and Chevy A-bodies built from 1964 to 1972. As you can see, we were still a long way off from having enough room for an overdrive transmission.
Before cutting any part of...
Before cutting any part of the body, you need to first locate the engine and the trans on the frame. This is easier with the body off the frame, the frame on jackstands, and the engine on a hoist. You may already have a good idea on your own project, but this was a clean sheet of paper. Key considerations are ground clearance, accessory drive layout, exhaust routing, and steering placement. On Mark's Tempest, none of this original A-body stuff made the cut.
Here, the engine centerline...
Here, the engine centerline is being placed in the center of the framerails with the help of a steel T-square. Once you find the ideal location for the engine/trans assembly, you'll want to take copious measurements between engine mounting points, trans mounting points, and the frame. These will help you fabricate the motor mounts and crossmember. You'll note that we're still a long way off from cutting the body. It can't be seen in the shot, but there's a floor jack under the trans to help establish the angle of the engine/trans assembly.
Meet Jeff Bachar of American...
Meet Jeff Bachar of American Muscle Cars (AMC) in San Bernardino, CA. All the handiwork we'll be showing is from this man. At this point, Jeff is figuring out how he's going to attack Mark's project. Based on the end result, you can see it pays to think about it a lot before you start cutting stuff up with a chopsaw.
We skipped a lot of steps,...
We skipped a lot of steps, but since this isn't about fabbing engine mounts, it's OK. Here is the finished passenger-side engine mount Jeff Bachar fabricated. From the chassis/engine measurements taken from the previous step, Jeff mocked up a model engine mount from cardboard, test fit it, then made the real item from 3/16-inch cold rolled steel plate. The aluminum adapter plate was cut from 3/8-inch, 6061 T6 aluminum billet bar stock and is 4.5 x 5.75-inch wide. This adapts the traditional small-block Chevy engine mount to the late-model LS2 block. AMC didn't want the oil pan below the crossmember (especially with the Air Ride suspension), so they didn't want to take any chances on aftermarket swap kit motor mounts.
The next step was fabricating...
The next step was fabricating a new trans crossmember for the 4L60E (made out of 1.5-inch diameter, .120-inch thick DOM steel tubing). The two critical measurements here are the longitudinal offset of the trans mount (the difference between the location of the original trans mount and the new 4L60E mount), and the vertical placement (to arrive at the mechanically correct driveline angle). Remember, the angle between the tailshaft and driveshaft must be complementary (180 degrees apart) to the driveshaft/pinion angle. Jeff used a tubing bender to get the crossmember shape just right, but a home builder could section some square or round DOM tubing for the same result.
With the engine and transmission...
With the engine and transmission in their final and fixed positions, the real work on the tunnel can begin. By lowering the body onto the frame with the engine and trans in, you'll get an idea where the interference occurs. Mark these areas first, then scribe or mark the minimum amount of trimming required to get the body on the frame. We stress the word "minimum" because you can always trim more later. It's far harder to add metal back.