Big Block Chevy Engine Bulid - The Street Beast Part 1

My last foray into big-block Chevy building was about a year ago when my students at UNCC needed a real budget motor for their drag race Camaro (see "Budget Big-Block," Feb.-March, 2005). Starting with a donated 454, we managed to build a flat-tappet, stock-headed 475-incher that made close to 500 hp and proved enough to propel the car to a best of 6.62/101.8 mph in the eighth. [That's deep into the 10s for you quarter-milers. -ed.] It was now time to move on to something a little more removed from the near-stock spec of the 475. After the success of their first big-block Chevy build, three of my students, Bruce Greer, Nathan Bornitz, and Dusty Kennett, were hot to build something a little more exotic without fatally rupturing a typical working guy's budget. It should be able to pull double duty, both on the dragstrip and, with the help of a small splash of race fuel cut with pump gas, be able to run fine all night on the street. What they wanted was a Street Beast.

T&L Engines of Busch engine fame had volunteered to do our machining and help out where possible on this project. This proved to be very much in our favor as T&L also produces a line of custom big-block Chevy crate motors. These are all based on about half a dozen dyno-proven combinations ranging from 468 to 640 inches. The plan was to have the students spec out the Street Beast in its entirety, then have Lloyd McCleary, the boss at T&L, critique the proposed spec. Basically, the Street Beast had to be affordable, reliable, street drivable and, of course, fast. If I taught my students right, they should be able to come up with the best compromises to meet all the aforementioned criteria. This chart is what they jointly came up with:

With torque and horsepower targets of 620 lb-ft and 650 hp, this spec looked good to me, but I told the guys to check it out with Lloyd as he builds motors like this every week. Here was his take on it: "The Dominator carb, with its intermediate circuit that fills in between slow cruise and flat-out makes the Dominator an ideal big-block Chevy carb and the cubes can definitely use this carb's big cfm to their advantage. The Dominator gives away virtually zero to the smaller 4150-series Holley down low, but it certainly makes more at the mid and top end. Good choice, as is the manifold. The Dart Iron Eagles have the same chamber and port configuration as Dart's aluminum version and they make good power right out of the box. Basic porting will probably help to the tune of 20 or so hp. Valvetrain: great combination choice here with the beehive springs as the pivotal pieces. This should be a 50,000-mile valvetrain. The cam spec itself shows some serious research has been done here as most big-block cams are, to a certain extent, inappropriately spec'd for the job. For many crate motor builds, the day is only saved by the engine's big inches. The rest of the parts look to be compatible with the goals in mind. This should be a good engine as it is very similar to ones we have built. Bearing in mind the goals, I would say build it--as is."

With Lloyd's approval in hand, our team was ready to start and the first job was finding a suitable block that would go 125 thousandths oversize to give us the 482 inches.

Selecting The Block
First, it should be said that had the budget stretched a little more, we would be looking at a Dart block for this project. Maybe next time, but for now it had to be an OE block. Since T&L builds big-blocks and has cores on hand, the first place we looked for a block was there. Most big-blocks are good to hop up, but a little more selectivity is needed if it is to be bored .125-inch oversize. This is where the sonic tester comes into its own. The blocks here had been visually inspected to see they were OK for use and then cleaned. A block was picked at random and the job of testing it for cylinder wall thickness at the top (1 inch down the bore), middle, and bottom was started. Here we had a measure of luck as the first block tested met our requirements. From here, the block went directly on to T&L's boring machine. Various fixturing was used to ensure the bores were correctly positioned over the main bearing centerline.

When all was ready, the bores were hogged out to within about five thousandths of finished size and the whole operation moved on to the hone. With a deck plate in place, the block was finish-honed to size with the finish required for the Total Seal rings to be used.

While the block prep was being done, UNCC student Bruce Greer was busy on the mill prepping the dome on the Ross pistons. Some 250 thousandths was machined off to encourage flame front propagation over the piston crown. This reduced the crown from 36cc to 30cc. In conjunction with about 70 thousandths off the heads, this resulted in a quasi-streetable 12:1 compression ratio (using a 1-to-10 mixture of 112 Octane race fuel cut with 93 octane pump gas). Along with the piston prep, the rods were lightened, reconned, and balanced. This was handled by Dusty Kennett. For the record, stock big-block rods are, though a little on the short side, plenty tough if somewhat heavy. Fortunately, there is scope for some serious lightening. With Dusty's beam polishing, removing most of the balance pad on the small end and cap milling, some 90 grams were removed. After all the grunt work was done, the caps and rods were refaced at the parting line--equipped with ARP bolts and re-honed to size. The pin end was also made floating by honing it out. With the lubes used, a steel-on-steel rod end would still be good for 100K. When all machining and such was done, Dusty balanced the rods end-to-end to less than a gram.

For a crank, we used a barley worn stock cast iron piece that seemingly had rarely been taxed in its entire life. A check on the journals revealed that we would have to grind 10 thousandths off the mains to get clearances where we wanted them. With that done, the crank, rods and pistons were balanced with a Professional Products external balance damper in place.