BUILDING BLOCKS (Part 2)
Laying The Groundwork For Your Engine
(To access Part 1, point your browser at http://www.maxchevy.com/tech/2007/ii_9-buildingblocks-1.html.)
Last month, we examined the GM Performance Parts CNC-machined Bowtie blocks (using a tall deck big-block as the example). We looked at how thick the cylinder walls prove to be and how straight various bores are. Recall that these CNC-machined Chevy blocks are checked and measured in multiple locations for each specific area of the respective bore (cylinder, cam, main bearing and lifter). We also examined the main cap hardware (in this case, splayed 16-degrees on the outer bolts found on the three inner main caps) and looked at the fuel pump boss (no small concern, particularly for a street-driven Chevrolet). We also took into account core shift – something that can raise havoc with any engine, high-performance or otherwise.
Keep in mind that GMPP offers similar components for standard deck height big- blocks, a wide array of small-block V8 incarnations, and several new pieces of hardware for the LS-series engine. And that doesn’t take into account the very specialized cylinder blocks destined for Nextel Cup or NHRA Pro Stock. There's information here any Chevy enthusiast can use.
Another difference between GMPP Bowtie big-blocks and their more pedestrian counterparts are the additional head bolt bosses--four per bank, eight total). Certain GM and aftermarket cylinder heads are engineered with the extra head bolt holes, or in certain cases, the heads can be modified to accept additional bolt holes. The result is better cylinder head clamping force. This really isn’t a dilemma for a low-compression, naturally aspirated engine combination, but if you add a bunch of nitrous oxide (or a combination of nitrous and high compression) or supercharge the engine, the compression ratio is in the stratosphere, so the additional head bolts prove to be a big bonus.
