What can you do with a big-block Chevy that hasn’t been done before? Well, for one thing you find ways of making it more distinctive than the rest. It doesn’t have to be the most powerful big-block Chevy ever done because there’s always someone with a pinch more poop. It just has to be that sweet combination of streetable performance with durability and an attitude. You want brute torque for a spine-decalcifying snap at the traffic light or at the dragstrip yet civilized cruiseability on the open road. This engine courts the edges of both streetability and a racing engine.
To get the sweet combination of both performance and civilized operation you have to amass the right combination of parts. We will tell you this going in—this is not a mild-mannered street engine. It is a rompin’, stompin’, street/strip powerhouse you can drive to the office yet have fun with on the weekends.
With 496 ci of displacement on hand coupled with 4.250 inches of stroke and 6.385-inch-long rods for generous dwell time are the bones necessary to make a classic Chevelle, Camaro, or Nova rock. Intimidating at a traffic light. Rock and roll time at the track. We’re working with Gregg Jacobson of PHD Speedcenter in Bakersfield, California, who understands what it takes to build real horsepower and torque into a vintage mill.
We’re building a good, old-fashioned Chevy fat-block with a radical mechanical roller cam, Brodix #RR BBR rectangular-port cylinder heads, roller rockers, Scat steel stroker crank, H-beam rods, Mahle forged and coated aluminum pistons (PN 1-42310BI), MSD ignition, Holley carburetion, and Edelbrock induction. This broad combination of proven performance parts are what make the big-block Chevy legendary.
Scat stroker kits are available with either a high-end forged 4340 crankshaft or Scat’s Series 9000 cast crankshaft and I- or H-beam connecting rods with either 7/16- or 3/8-inch cap screw rod bolts. For maximum durability Scat includes King, Federal Mogul (Speed Pro), or Clevite 77 rod and main bearings depending upon the application—with pistons and rings from SRP/JE, Ross, KB, Mahle, Diamond, and Probe. Ordering a Scat stroker kit from Summit Racing Equipment means you’re getting solid reliability for your Chevy big-block project.
We’re working with a Chevrolet 454 four-bolt main truck block (PN 14015445), which is a good foundation for the kind of power we want to make. It has been cleaned and Magnafluxed for cracks. Chevrolet produced this block casting from 1978-1990. Not all PN 14015445 blocks are four-bolt main. Make sure you’ve found a four-bolt main block before plunking down the cash. This is a brute block that can handle 500-plus horsepower.
Gregg Jacobson of PHD Speedcenter tells us block prep includes a full program of machinework, including deburring, milling the decks, line bore, piston-matched boring and honing, and honing the lifter bores for good oil control. Jacobson uses GE Glyptal coating on iron surfaces to both seal the iron and improve oil return flow.
Oil galley passages have been chased, tapped, and plugged for good oiling system security. You can never clean oil galleys even because there are always traces of debris. This is a good practice for any engine build in order to maintain oiling system security.
Jacobson stresses proper installation of the two-piece rear main seal, which is a heavy-duty Fel-Pro seal. The seal lip must be installed toward the crankshaft, which keeps the seal lip against the crank journal. Jacobson uses Permatex’s The Right Stuff between the seal and block, with a small dab at each end. Seal tips are staggered away from the main cap parting lines to prevent leakage.
For a mean street/strip demeanor, Jacobson has opted for the COMP Cams mechanical roller cam with 110-degree lobe centers (PN 11-772-8) and a lot of lift and duration for deep breathing at high rpm. You get a lumpy idle along with a good broad torque curve from 3,000-7,000 rpm. Jacobson was anticipating 600 hp and comparable torque.
Because Jacobson thrives on durability, he opted for a Scat 4340 steel crank with a 4.250-inch stroke and 6.385-inch H-beam rods topped with Mahle forged pistons with a mild dome. The result is 496 ci and a tremendous amount of torque from the 4.250-inch stroke. These rods offer a good rod ratio and allow plenty of dwell time and cylinder fill/scavenge time at each end of the bore.
PHD Speedcenter’s piston prep includes the installation of plasma moly iron rings on top, cast rings next—positioning the endgaps at 90-degree intervals. Rings and pistons are coated with engine assembly lube to ensure a nice, wet startup. When Jacobson fires this engine on the dyno, he will do a break-in cycle to seat rings and bearings before doing power verification pulls.
Once all eight pistons are in their bores, Jacobson will check deck and compression-height to get an accurate assessment of what he has for compression ratio. Compression ratio was expected to be 10.0:1 for use with pump gas.
Connecting rod bolt torque is 63 lb-ft in one-third values one cap at a time. The rotating assembly is checked for freedom of movement as Jacobson torques rod bolts.
Crankshaft endplay is checked and should of 0.004-0.008 inch in a high-performance application.
When you’re building a street/strip big-block Chevy you have the option of ARP studded main caps, which is suggested for better bottom-end security. You may also go with ARP main cap bolts like Jacobson has here, which provide a much better level of main cap security than stock bolts. Main studs keep caps from wandering much better than bolts.
Because we’ve gone with a Scat stroker kit the very first order of business was the mockup phase, which we did not photograph, but will explain here. A mockup pre-assembly phase should be performed early on without piston rings installed to make sure rods, bolts, and counterweights clear the block and oil pump.
Jacobson opted for the COMP Cams adjustable double-roller billet timing set (PN 8110) from Summit Racing Equipment for this 496 project, which enables him to adjust valve timing quickly and easily.
This close-up view of the adjustable billet cam sprocket demonstrates how easy it is to adjust valve timing.
We’re framing in the adjustable billet timing set with the COMP Cams three-piece aluminum timing cover (PN 312) from Summit Racing Equipment. Cool thing about this timing cover is access to the adjustable timing sprocket.
True top dead center and cam specifications are checked prior to the cylinder heads being installed. We found our cam to be spot-on with the cam card.
The cam button is installed next, which will keep the cam stabilized.
Cam sprocket bolts get Permatex thread locker and are torqued to 20 lb-ft.
With the COMP Cams three-piece cam cover installed, Jacobson checks camshaft endplay, which should always be checked. That’s what’s good about this timing cover. It enables you to check endplay with the cover on.
When we first saw these Mahle pistons, we were convinced this engine sported a lot of compression. However, the Brodix heads have large 119cc chambers, which have been massaged to 123 cc. Compression ratio is a mild 10.3:1 for operation with pump gas.
Jacobson is going with Fel-Pro Permatorque head gaskets from Summit Racing Equipment. Although they say these head gaskets don’t require a retorque Jacobson gives them a retorque anyway for extra added measure after the initial fire-up. Jacobson stresses clean mating surfaces because even the tiniest debris can cause leakage.
Jacobson likes the Super Damper from ATI. It is SFI rated and delivers smooth function at all rpm ranges. The Super Damper’s primary purpose is to act as a crankshaft shock absorber at the end of the crank to absorb crank twist.
These Brodix Race-Rite Rectangular-Port cylinder heads (PN RR BBR) are an easy bolt-on for virtually any big-block Chevy. They bolt right in place of the stock iron heads without special modifications or piston changes.
Jacobson performed some of his own custom port and chamber work on these Brodix heads to reduce turbulence and eliminate hot spots.
With the Fel-Pro Permatorque head gaskets in place, Jacobson seats each of the Brodix heads. Jacobson doesn’t cut corners when it comes to valvetrain components. He has specified COMP pushrod guides with ARP 7/16-inch rocker arm studs.
Jacobson has opted for a Speed Pro high-volume oil pump along with a Moroso deep-sump pan and pick-up to ensure abundant volume at high rpm.
We like the COMP valvetrain components encompassing Pro Magnum full roller rockers, which have been properly adjusted to 0.016-inch intake and 0.018-inch exhaust. Valvetrain geometry has been checked and confirmed using the correct length one-piece 0.080-inch thick-wall COMP Cams pushrods.
Our completed 496ci stroker looks sharp.
PHD Speedcenter has the 496 on a run stand for that initial fire-up to check vitals. Jacobson expects to see 600 hp at 6,500 rpm and nearly 600 lb-ft of torque at 5,000. That’s a 950-cfm Holley 0-80496-1 carburetor atop an Edelbrock Performer RPM Air Gap (PN 75624) with Endurashine. A complete MSD ignition system fires the mixture.