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Pontiac SD-455 Block Repair - Damage Control - Pontiac Tech
 Anyone familiar with Second-Gen...  Anyone familiar with Second-Gen Firebirds knows the importance of this block code. "XD" signifies a '73 Super-Duty 455 engine backed by an automatic transmission. This particular block is the numbers-matching unit from a '73 Trans Am owned by Steve Schappaugh of Lincoln, Nebraska. It's one of 252 SD-powered T/As built that year-180 of which were backed by an auto. The engine was recently disassembled for an internal repair. |  The intermediate shaft transfers...  The intermediate shaft transfers motion from the distributor to the oil pump, and the piece on the left is how a typical shaft should appear. The piece on the right is what occurred when it fell into the crankshaft counterweight during distributor removal and was forced into the block at cranking speed. Because the engine was turning so slowly, little collateral damage occurred, but total disassembly was required. |  From this view, looking inside...  From this view, looking inside a typical Pontiac block, we see the purpose of the intermediate-shaft loop. It simply maintains the shaft's position when removing or reinstalling the distributor. Notice the close proximity of the crankshaft. |  Because this portion of a...  Because this portion of a typical Pontiac block isn't under much stress, the intermediate-shaft loop isn't heavily reinforced. Every Pontiac builder we spoke to says that, though rare, they've seen situations where a portion of the loop had broken away, and that it was usually the result of major mechanical failure or human error. |  When reinstalling an ignition...  When reinstalling an ignition distributor, very few hobbyists look down into the block unless the intermediate shaft doesn't engage the distributor gear properly. If we had, we certainly would have noticed this broken portion of the block. After this experience, you can bet we'll be peeking inside every engine we install a distributor into! |  Looking upward provides a...  Looking upward provides a clearer view of what's missing. |  Chuck Willard, of Willard...  Chuck Willard, of Willard Auto Machine in Omaha, Nebraska, created this step bushing for the Super-Duty block. The Outside Diameter (OD) of the upper step measures 1.25 inches, while the OD of the lower step measures 0.688 inch. The Inside Diameter (ID) measures 0.520 inch, and easily accommodates the tapered portion of the intermediate shaft, which measures 0.475 inch in diameter. |  Using a mill, Willard machined...  Using a mill, Willard machined what remained of the intermediate-shaft loop to the exact dimensions of the bushing. The upper surface of the block was machine-faced with a 1.25-inch diameter bit, 0.125 inch downward to accept the bushing's upper step. What remained of the loop's ID was enlarged enough to maintain an interference fit with the bushing's lower step. |  |  The bushing was then lightly...  The bushing was then lightly coated with Devcon industrial strength epoxy, pressed into place, and then liberally coated to effectively seal it in. With total functionality restored, this Super-Duty block can be considered as good as new. |  While the engine was apart,...  While the engine was apart, Schappaugh elected to install new pistons and piston rings, and rod and main journal bearings.The cylinders were bored 0.035 inch to a diameter of 4.185. |  After reassembly, Willard...  After reassembly, Willard placed the fresh SD-455 onto his Land & Sea DYNOmite engine dyno, broke in the hydraulic flat-tappet camshafts, and measured its output. |
The relatively stock SD-455... The relatively stock SD-455 cranked out 405 hp at 5,100 rpm, and 478 lb-ft of torque at 3,900 rpm. Average horsepower and torque between 3,000 and 5,500 was 360 and 448, respectively. You can bet that's enough to put a smile on any driver's face!
Pontiac Solstice Research
Get updated on all your car buying needs from safety features, to specs, to crash test ratings and options. Get all the information you need if you are interested in buying a new car like the Pontiac Solstice. The L4 standard engine in the Solstice gives you 173 horsepower with an estimated 22 mpg. It has a trade in value of $15,948.00 which should come in handy when you go to shop for your next car. The Pontiac Torrent and the Pontiac G6 are other vehicles that might interest you.
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