It was one of those emails from your boss that you fear: “The AMD Chevelle is going on the Hot Rod Power Tour. Make sure it’s ready and won’t break down.” Not noted, but clear as day, were the words “or else!” Oh, and it had to be ready in about a month.
Now, while cosmetically perfect, our resident ’67 SS396 had just gotten a heart transplant and a new electronic overdrive transmission. Its fresh 402-cum-413 had been installed, as had a TCI 4L80E, but like any project, there were odds and ends to address. There was an intermittent stalling issue with the trans in gear at idle, which dictated the idle be set at 1,100 rpm, way to high our mild combo. Even in moderate weather and humidity, the Rat ran way too hot in traffic, and it did not get much cooler cruising at highway speeds. We had the typical assortment of quirks, leaks and issues common to any fresh build, not to mention we’d yet to run-in our rebuilt 12-bolt, which would need a post break-in fluid change. There was a transport truck coming to Tampa to pick it up and there were no mulligans if that A-body wasn’t on it when it headed to Power Tour’s starting point in Concord, North Carolina.
The clock was ticking
The first order of business was to put a few hundred miles on it, never a hardship when you’re talking about a classic muscle car. When AMD’s restoration center rebuilt this A-body after dragging it from a field, it was significantly better than when it left Chevy’s assembly line. The doors and trunk shut with the same authority you’d associate with a expensive luxury car. Every body panel lined up perfectly. But there’s nothing that makes you more self-conscious than having people admire your baby at a traffic light and the engine suddenly dies. And if the temp gauge was on the very high side of normal in moderately warm weather, in June Power Tour traffic it would go off like a tea kettle.
We tried different thermostats (180, 160, none at all), but this made no difference. The radiator was a brand-new repop piece, but it sure was thin. Online we found that there were (at least) three different sized radiators for the SS396, and ours was for a 325-horse model. Frankly, it just seemed puny. Maybe a factory original piece would have worked better, but this thing was in way over its head. We put in a phone call U.S. Radiator and explained our problem to Don Armstrong, the owner of the company. He assured us he could do a radiator that looked stock that would cure our ills.
The proof was in the pudding, U.S. Radiator delivered a drop-in replacement. We moved the standard-duty radiator to the warehouse and dropped in a new U.S. Radiator 25-inch-wide, four-row piece and the AMD Chevelle hasn’t had a cooling problem since.
While waiting for the radiator to arrive, Tampa tech center manager Darrell “the Torch” Kunda got to tweaking, twerking, and tightening everything under the hood. He fixed numerous snafus from the engine/trans swap. Suddenly, it was all coming together. The stalling problem was solved by hooking up the PCV system.
We also discovered a coolant leak at the intake manifold. The 360-horse factory iron manifold we were using would not seal 100 percent because of pitting. The Torch was able to get rid of the pitting, but it was so bad the manifold could not be used. At this point, we decided to skip the antique stuff and go with a good aftermarket dual-plane. A call to Weiand had an aluminum Street Warrior dual-plane intake jetting to our offices overnight. The low-rise design is designed to make power in the idle-5,500 rpm range, perfect for our slightly massaged, smog-era, oval port heads. Among its numerous cool features are a dual-flange design, which accepts Quadrajet or Holley-style carburetors. The Weiand piece took 40 pounds of dead weight off the nose and added significant horsepower and torque.
Finally, we added a set of lap belts from National Parts Depot. No, the car didn’t have seat belts, front or rear. Eventually, we may go with a set of three-point harnesses, but these would do in a pinch.
We’re happy to report that the AMD Chevelle was completed on time, traversed 1,602 miles on Power Tour without incident (and hundreds more since in got back), and was a hit wherever it went.
01. In keeping with the AMD Chevelle starting out its new life as close to when it first left the factory, a pair of National Parts Depot lap belts were installed.
02. Even if the radiator isn’t going to be removed, the coolant should be drained to avoid flooding the intake valley with coolant. Future improvements to the AMD Chevelle include replumbing these cooling lines.
03. After removing the top and bottom radiator hoses we removed the bottom two mounting bolts on the core support holding the radiator in and then loosened the top two bolts.
04. By leaving the top two bolts almost at the point of falling out, with only a few threads clinging, it made removing the radiator a one-man job. Installing the new radiator was a reversal with thin cardboard protecting the fins going in.
05. Virtually undetectable in outward appearance from a stock factory radiator, the U.S. Radiator four-row unit has twice as many fins and tubes, providing up to a 30 percent increase in heat exchange. This core is 25-inches wide (2 inches more than what we had). The OE radiator is a three-row design, while this is a four-row piece—plus the rows are 3/8-inches wide instead of 1/2-inch, which allows for more tubes. This dropped the operating temps significantly on the factory gauge. Overheating never became an issue, even in bumper-to-bumper traffic.
06. Swapping out the stock cast-iron intake manifold began by removing the air cleaner and carburetor.
07. Next, the Pertronix distributor and ignition coil were removed, noting the position of the rotor with a mark on the firewall so initial timing would not have to be reset.
08. The reusable ARP intake manifolds bolts were removed, then a crowbar was used to carefully pry the intake manifold upward and off. Note the (four) raised square prizing point at right of the socket.
09. After thoroughly scraping, cleaning, and removing all traces of the old intake gaskets from the intake port faces and block, Permatex 598B Ultra-Black RTV was applied evenly.
10. The Torch used his fingers to spread Permatex 598B Ultra-Black onto the intake ports, which we don’t recommend. Use rubber gloves when handling this stuff.
11. Close attention was paid to gluing the intake manifold gaskets to the port faces. At this point we screwed all of the ARP intake bolts in to ensure the intake gaskets were properly aligned.
12. In addition to a substantial horsepower increase, tossing the 360-horse cast-iron intake in favor of the Weiand Street Warrior resulted in an appreciable drop in weight—no less than 40 pounds. That alone will be worth a ton in performance at the track. The dual bolt pattern allows you to use either a Quadrajet or square-bore carburetor. We have a 750-cfm Holley.
13. Installing the lighter Weiand aluminum intake without disturbing (shifting) the gaskets was accomplished by hovering directly over the bolt holes and then lowering it directly into place.
14. Following a tightening sequence chart, the intake was torqued to spec in three stages. Then the fuel and ignition systems were reinstalled, and fresh coolant added. Our coolant leak was cured.
15. The AMD Chevelle’s baseline dyno pull with a stock cast-iron intake produced 261.03 horsepower and 260.42 lb-ft of torque. With changing to the Weiand intake manifold the numbers climbed to 307.70 horsepower and 298.54 lb-ft of torque.