TO refresh your memory from last issue, the SD-455 that you see before you belongs to HPP contributor Melvin Benzaquen. We were using it as a mule for a fuel-injection swap into his '74 T/A when it expired on the chassis dyno during baseline testing. Cracking open the famed powerplant revealed a poor rebuild was the root cause of the engine failure.
Presented with the opportunity to rebuild the engine as well, the owner decided to upgrade the powerplant for reliability and employ some modern technology, so he sent the engine to RaceKrafters. That quest began in Part I with basic machining using state of the art equipment. Cylinder-wall finish and the valve-job procedure were notable technological improvements, fully explained in the first installment to go along with the basic machining and cylinder head porting.
In this issue, the engine will be assembled, and a Comp Cams hydraulic roller cam will be employed to exploit its advantages, such as lower friction and more aggressive ramps to open and close the valves more quickly by realizing more lift per degree of rotation. Craig Wise of RaceKrafters did all of the assembly work. He showed our Pontiac the same care and execution to detail that would be provided to a 1,000hp drag engine.
In the next installment, HPP will work with RaceKrafters to dyno test the engine with a carburetor and then with the high-tech EFI system from Mass-Flo EFI, but first we need to get some wrenches swinging!
Due to the fact that the engine...
Due to the fact that the engine had been bored at least one time before it got to RaceKrafters, a custom piston measuring 4.181 inch was required to fit the 4.185-inch bore (0.035 over 455), so a forged SRP slug was made to order. Eagle's H-beam forged-steel connecting rod has a stock length of 6.625 inches but was made with a bushing in the small end to support a floating wristpin. The engine's owner chose to save the factory SD rods and run aftermarket ones instead. Piston rings are from Perfect Circle.
During the cylinder-honing...
During the cylinder-honing procedure, the piston-and-ring set are assigned to a specific bore. With the cylinders finished to match the rings, the latter were installed, and the gap was checked using a feeler gauge.
With the rings measured, the...
With the rings measured, the end was ground on an electric filing machine to obtain the desired dimension. The top ring was set for 0.017-inch gap, while the second ring was machined for 0.015 inch.
New cam bearings were installed...
New cam bearings were installed and should always be a part of any rebuild. Cam-bearing installation is not hard, but it is tricky if you don't do it all the time. Even if you plan on assembling your own engine, HPP recommends having the machine shop install the cam bearings.
A final check of the main...
A final check of the main cap size with the bearings installed will confirm the clearance. The machine work was done for a clearance between 0.0029 to 0.0035 inch for use with the Eagle crank. The SD's factory four-bolt main caps will be retained.
The connecting rods were set...
The connecting rods were set up for a clearance of 0.0027 to 0.0030 inch. A dial bore gauge is used to determine the bearing clearances, as shown.
Whenever working on a connecting...
Whenever working on a connecting rod, a special rod vise is required to prevent damaging the component.
Piston-pin to connecting-rod...
Piston-pin to connecting-rod clearance is very important, especially with a floating wristpin. The SD was machined for a clearance of 0.0008 inch.
With all of the measurements...
With all of the measurements confirmed for the third time (checked during the machining procedures and again during a preassembly of the engine), it was time to assemble the rods to the pistons.