When it comes to big-block Chevrolet performance engines, they come in all categories. With virtually boundless components from the aftermarket, the high-end of the spectrum is nothing short of exotic. Eric Weingartner took an alternate approach, looking to make the most of what can be considered everyday-style parts in a budget 496 combination that can swap blows with the big boys. The engine was built for our annual engine-building competition, the AMSOIL Engine Masters Challenge, an event that had this engine competing with the best efforts of some of the most talented engine builders in the business. Considering the restrained component selection of this engine combination, Weingartner’s solid mid-pack finish was proof enough of the engine’s worth.
Want to build big power on...
Want to build big power on a budget from a big-block Chevrolet? Take a factory four-bolt block and stuff it with a Scat 4.25-inch crank to make 496 cubes, tie it in with ARP studs, and then finish it off with a set of forged Probe pistons hanging from Scat forged I-beam rods.
Build It
Starting with a factory four-bolt main block, Weingartner began with a modest but capable foundation. Sure, an aftermarket block would have been a step up, but for the required powerband, the OEM GM block was a far more economical choice. As Weingartner tells us, “I would have liked an aftermarket block with a 4.500-inch bore, and run a little less stroke, but that doesn’t work as well in the competition because you need that torque down low.” The block was upgraded with ARP main cap fasteners, and otherwise left pretty much as Chevrolet built it. A key to making the used block work, however, was in the detail and accuracy of the machining. Here, Weingartner gives plenty of credit to his machine shop, Dunsworth Machine. They did all the work on the block, with a full block prep including clearancing for a stroker crank of up to 4.375 inches. Dunsworth also provided the dyno services for the performance tuning and development of the finished engine.
Who says a bulletproof bottom...
Who says a bulletproof bottom end has to cost a fortune? This big-block uses readily available parts such as Scat 6.385-inch I-beam rods and Probe forged pistons—affordable parts that are made to go the distance.
While the block began as a stock production piece, the parts that filled it are strictly aftermarket. Here, Weingartner looked to gain maximum value by selecting parts that would do the job reliably over the long haul, while refraining from stepping into the more high-dollar equipment. Starting with the crank, Weingartner went with a Scat 4340 forged steel piece, with a stroke length of 4.250 inches. This is a popular off-the-shelf piece, making it an excellent value, especially when you consider that it’s practically bulletproof. That’s one of the keys to Weingartner’s budget approach—using readily available and proven parts combinations. Complementing the crank is a set of Scat 4340 I-beam rods measuring 6.385 inches, with ARP 2000 capscrews. Again, these are commonly available parts offering real value in terms of service durability versus cost.
Although this combination...
Although this combination carries a crank with a 4.25-inch throw, Weingartner had the block clearanced for a 4.375-inch stroke. This allows the same block to be used at even greater displacement.
Filling the bores are a set of Probe small-dome forged pistons, with conventional 1/16-1/16-3/16 ring grooves. Where Weingartner decided to go with a more esoteric setup was the rings. The bores are sealed with a custom low-tension set of Total Seal gapless top rings. Weingartner says, “I was afraid I might detonate and get too hot, butting the rings. With the gapless, I was able to open the ring gaps for more insurance, and still get the seal. With the low tension, they weren’t dragging much. I remember when I was turning the engine over with all the pistons in, it was only about 12 lb-ft to turn the engine over.”
Weingartner’s specialty is in cylinder head porting, and here he had a chance to put that expertise to work. Sure, the easy path to high airflow would have been a set of expensive CNC-ported aluminum race heads. Weingartner, however, started with a modest set of RHS cast-iron 320cc heads. Weingartner explains, “It took a lot of trial and error, and when I first got done with the prototype, it was perfect. The RHS heads have a big and long short-side turn in the port, which really helps the low-lift flow. They are really good down low, and they are not that big. We got it digitized and ran the heads CNC ported. I had to angle mill the heads .112 inch to get the compression ratio up, but the angle milling hurt the flow. I spent lots more time grinding to get it back where it was, and then had to use epoxy to fill it to get the runner volume back down.”
Filling the heavily milled...
Filling the heavily milled chambers is a set of REV valves, measuring 2.250-inch intake and 1.88-inch exhaust. Weingartner tells us the 2.250-inch valve works better than a larger valve with a limited bore size, while for the exhaust valve he favors the tulip profile.
A set of Total Seal rings...
A set of Total Seal rings were employed to seal the bores. These rings allow the endgaps to be set to a safe level—even under detonation conditions—while maintaining the combustion seal equivalent to an effective endgap of zero.
Working in tandem with the...
Working in tandem with the Melling pump is a Hamburger steel oil pan. The pan comes with a built-in windage screen and crank scraper, as well as an intricate series of internal baffles to control the oil.
To achieve a finished port...
To achieve a finished port volume of 314 cc after porting, the floor of the port was filled with epoxy. As Weingartner explained, the low-flowing, or “dead” areas, were filled.
A standard stock-replacement...
A standard stock-replacement Melling big-block Chevy oil pump was used to provide the lube; however, Weingartner took the time to port the internal passages for improved flow. The result is a low-drag oil pump that provides plenty of lube.
The Probe pistons feature...
The Probe pistons feature a dome volume of 14 cc. To get the targeted compression ratio of 11.3:1 required substantial angle milling of the cylinder heads. Eric Weingartner cut the valve notches .030 inch to achieve adequate piston-to-valve clearance.