Engine-build primers are a main component of the technical aspect of HPP. We pride ourselves on furnishing the readership with detailed information that can be used on their Pontiacs. We've covered the gamut from a basic engine freshening to all-out drag-race powerplants and everything else in between. This time, however, we're doing something different.
We went to Jim Taylor Engine Service (JTES), a well-respected Pontiac shop, to document the freshening and modifying of a 455 for a customer, Bill Wise from Queens, New York. His '74 LeMans is a street/strip car that features a rollcage, a complex stereo system, and other accoutrements. The Pontiac weighs approximately 4,300 pounds and is driven everywhere it goes. The previously Taylor-built engine was strong-proven by numerous 12.54 timeslips-and reliable, with more than 10,000 problem-free miles of street/strip service.
But Bill wanted more-an 11 second e.t. was the goal, and Jim Taylor Engine Service believed it could accomplish that.
The trick is to achieve the customer's goals, despite the heavy race weight and without sacrificing the street driveability of the Pontiac or adding nitrous. That means engine vacuum must be good; only straight pump gas exits the carburetor boosters; and it has to do everything a stocker does-just go a lot faster.
Over the years, the term street car has become skewed, since to many magazines it means a license plate, windshield wipers, and a rearview mirror. HPP's definition of a street car is one that can start in all weather, sit in bumper-to-bumper traffic and idle, and the key can be tossed to anyone with a driver's license with no concern for hurting the engine. It also has to be impressively quick-a tall task for a Pontiac that weighs more than two tons.
The Plan
The traditional means of making easy power-raising the compression ratio, and installing a larger (more aggressive) camshaft-isn't acceptable since it diminishes the car's streetability. Thus, Jim Taylor Engine Service needed to further dial-in the already refined 455. This meant an all-out attack on the minute details of the engine.
When building and blueprinting an engine, there are higher levels of tolerance. Extreme attention to detail is nice, but as with anything, a cost/benefit ratio needs to be established. For example, when porting a cylinder head, you can spend 100 extra hours and only pick up a few cfm, which may yield 10 hp. The standard protocol would be not to invest that amount of time because you don't need it. But instead do a good street port and look for the power elsewhere, such as in the cam or compression ratio. The customer has a good product within his budget and everyone is happy.
In contrast, the world of NHRA Stock and Super Stock Eliminator engine building takes the exact opposite approach. Since the rules limit the modifications, every last detail of the engine needs to be machined and assembled to perfection. [A task that takes a huge investment in time and knowledge but allows the relatively large number of stock parts to produce more power than what the factory did.] Though not a Super Stock engine, JTES applied many of the same edicts to this Pontiac, which makes it a unique educational experience for our readers.
Due to the nature of the rebuild, we chose to skip the traditional photos of the crankshaft being dropped in or the assembly of the cylinder heads and other parts. Instead, we spent three days documenting some of the exacting procedures employed on this engine.
The engine-block water passages...
The engine-block water passages were partially filled with Rokblock. This is done not only for strength and to limit bore distortion, but also to decrease the amount of coolant in the lower portion of the engine. According to Mark Erney, the engine will run cooler because the incoming coolant goes to the top (the hottest part) of the cylinder where combustion takes place. The first step is to completely level the engine block (front to back, left to right) on the stand with the torque plate installed.
After mixing, Rokblock was...
After mixing, Rokblock was poured into the engine through the rear core plug and the front water passages. Quick and careful execution is required during this procedure. Since the subject engine is for a street car, it was only partially filled, just to the bottom of the block-side freeze-plug holes.
The stock 4.210-inch stroke...
The stock 4.210-inch stroke nodular-iron crank was retained, as were the Crower connecting rods. All were carefully checked over and measured since they were going to be reused. New bearings were fitted.
Piston skirts and crowns were...
Piston skirts and crowns were coated by Swain Technology. The thermal barrier on the top helps keep heat from the ring package and instead uses it to expand against the piston for potentially more power. In theory, it also helps quench detonation by increasing the flame speed. The skirts were coated with a dry film lubricant to reduce friction. Erney polished the piston tops with "0000" steel wool to improve the reflectivity of the coating.
The pistons use a full-floating...
The pistons use a full-floating pin that is held in place by a spring steel lock. Floating piston pins reduce internal engine friction.
Attention was paid to the...
Attention was paid to the piston-ring end gaps (second ring shown)-they were carefully created. Gapless rings were used for the top only for improved cylinder seal, and a lower-tension oil ring reduces friction and frees up some power. See the Engine Buildup Worksheet sidebar for specs.