Chevy released the Mark IV big-block or "Rat" in 1965 to replace its "W"-series motors. This new engine featured (among other things) new valve placement and combustion chamber design to increase volumetric efficiency at higher rpm. Starting with 396ci in 1965, Chevy eventually went up to 454 in 1970. In between, you could get a 402 and even an all-aluminum 427 with a single four-barrel that was grossly underrated at 430hp. The kings of the street in the power department were the 1966 427 L72 that was originally rated at 450 hp (it was knocked down to 425 later in the model year) and the LS-6 454 of 1970 that was also rated at 450 hp. Then came the GM Performance Parts crate engines, like the 502/502 and then the monster 572 in 2003 that laid down 720 asphalt-destroying horsepower.
Today, the world is your oyster when it comes to Rat-engine power enhancers, which makes surpassing the older hp ratings a lot easier. The aftermarket has embraced the big-block and you can get everything from a set of lifters to a stroker crank. We used our connections to find out what the newest products on the market are so you don't have to-you can thank us later.
Aerohead Racing offers a set of fully assembled cast iron cylinder heads for the 454/502 big-block engines. Utilizing new GM castings, these heads feature rectangular intake ports, machined 7/16 studs and guide plates, 2.190 or 2.250x1.880 stainless steel valves, 119cc open combustion chamber, 310cc intake runners, hardened exhaust seats, 0.580-lift springs, 7-degree locks and chrome-moly retainers.
ARP has just released two new bullet-nose head stud kits for World Products cylinder heads. ARP has added 23 new part numbers for World Products customers over the years. These kits include all necessary 8740 studs, chrome-moly washers and 12 pt. nuts for the application, and a 1/2-ounce pack of ARP Ultra-Torque fastener assembly lubricant. All ARP 8740 studs are centerless ground, heat treated prior to thread rolling and machining, and are nominally rated at 200,000 psi. Most studs are broached to ease installation and removal.
Callies just introduced the Magnum Series III crankshaft for Rats. The Series III features the company's new dual-arc leading edges that are designed to not only reduce crankcase windage, but lead to lower manufacturing costs, saving you money. Stroke ranges are available from 3.500 to 5.500 to accommodate an array of cubic inch configurations. Also be on the lookout for the Callies Ultra connecting rods coming soon.
Callies Performance Products