The Pontiac division of General Motors met an untimely demise in 2010, but in the glory days of American muscle, the marque defined an era. Pontiac was a brand synonymous with performance, climaxing with the breakout GTO intermediate that launched the muscle car era, a position reinforced by worthy Firebirds, Bonnevilles, Catalinas, and Gran Prix model variants through those years. Unlike the products of the corporate era, Pontiac muscle was propelled by distinct Pontiac engines. Those engines were known for outstanding street power and helped build a legacy that lives on today. While the last true Pontiac engine was cast in 1981, these engines retain a dedicated following, and aftermarket parts support has never been better.
Mike Semchee is one of those loyal Pontiac enthusiasts, and for our annual engine-building competition, the AMSOIL Engine Masters Challenge, he represented the faithful with a true Pontiac entry in the Street Division of competition. Although in today's world it is entirely possible to build a high-performance Pontiac engine combination with all aftermarket parts, Semchee looked to base his build on traditional Pontiac iron. The result is a stout street Pontiac that makes use of an authentic Pontiac foundation, while upping the ante on modern-era horsepower.
Semchee started with a production base, beginning with an OEM Pontiac engine as the core. The basis is a factory 400 block typical of those fitted to an original muscle Pontiac. As Semchee jokes, the 1972 casting is considered a late-model piece in the Pontiac world, "I tell everyone I used my ‘new' block; it is a 1971 GTO block. These have a factory bore of 4.125 inches. I just gave it a standard overbore, but over the years of freshening it up, it grew a little to the current bore size of 4.157 inches."
Although Semchee modified the factory block for increased strength, it retained most of its OEM content. As Semchee explained: "The Pontiac blocks are strong. I did fill it, but they are very strong. I filled the block to the bottom of the water pump hole. This keeps the cylinders more stable and stronger. The block has the factory two-bolt mains. I put a lifter bore brace in it because the bores are in the open and if you run a really aggressive cam you can bust them out, so I made my own lifter bore brace. I machined four individual pieces that fit under the plates and epoxied them in and put the bars on top to hold them. I had my block machined at Crank and Sleeve Shop in Girard, Ohio. They do what I ask them to do. They do excellent, perfect stuff."
To go along with the factory block, Semchee looked no further than OEM equipment for the crankshaft: "The crankshaft is a factory unit, in fact, it is the original crank that came out of this block. I sent it to Lunati to have it Magnafluxed, shot-peened, and ground. The OEM cranks are good and strong. I've never had a problem with the crankshaft. It is a nodular iron unit, and is the original crank for this block."
Things altered from OEM include the rods and pistons, as modern aftermarket pieces provide the durability and performance that the stock parts cannot match. The rods are Scat H-beams in the OEM 6.625-inch length. As Semchee tells us: "They are bulletproof. You'll never have a problem with those in a Pontiac motor, at least for what we are doing." The pistons are from JE, but received substantial modification from Semchee for this specific application: "I could not get what I needed for the piston shape, so what I did was I ordered the pistons as flat-tops with valve reliefs, and machined the shape of the combustion chamber and made it a spherical dish. When the fuel burns in a spherical dish configuration it requires less timing and makes more power." The rings are also from JE, with .043-inch compression rings and a 3mm oil ring. Semchee notes: "The JE piston pins are much lighter than those from Pontiac; the Pontiac pins were very heavy. With the lighter pins it revs quicker and makes more power, and there is a lot less strain on the rotating assembly."
The bottom end of the engine was sealed with a full-length "bathtub" style oil pan from Charlie's Oil Pans. The odd choice of pan configuration was to take advantage of the liberal rules in effect for the 2012 EMC competition, though as Semchee tells us, the majority of the oiling system is OEM Pontiac: "I used the huge pan to keep the windage from the crank down and prevent wrapping all the oil up. I was advised by Charlie's not to use a windage tray with that pan, but I filled the pockets in the block at the pan rail to keep the oil from splashing back into the crank. The only thing I do to the factory oiling system is take the top half of the main bearing and machine it to match the oil passages in the block. I have never had a problem with the OEM oiling system—there really is no trick there. I just put a little .030-inch hole in the screw-in plug at the back of the motor near the distributor gears to help to keep them oiled."