"We're calling it The Hellcat Killer", says Mike Petralia, owner and chief engine builder at Hardcore Horsepower & Dyno in Franklin, TN. "It's a BBC designed for your classic GM muscle car or truck to run down those pesky late model tug boats. And it'll beat 'em with a carb, or EFI, on pump gas, and without the need for any boost or chemical power adders". This daily drivable-engine will be the new King of the Streets because of its hydraulic roller cam too. And it'll fit in just about any old iron with maybe just a small hood scoop. Trucks and Tri-5s are no problem.

For this build Petralia relied on the proven strength of a Dart Big M Sportsman block. It features Ductile Iron splayed  4-bolt main caps and vastly improved oiling over factory GM blocks with a true priority main oiling system. It has stepped oil galleys to increase flow to the crank at higher rpms and a front oil crossover that eliminates internal oil leakage around the distributor. No need to worry about distributor shaft o-rings with these blocks. Blind head bolt holes keep water from mixing with the oil. And a 2-pc rear main seal makes oil pan selection plentiful. Dart performed all the machine work on the block including boring it to 4.600-inch followed up with a torque-plate hone finished for Plasma-Moly rings. They also finish-milled the decks true and parallel to 9.800-inch for a Mr. Gasket Co. composition-type head gasket. And they installed all the cam bearings, brass freeze plugs, and locating dowel pins for the oil pump and timing cover too.

You can't expect 850hp to provide much longevity in a stock Chevrolet  block. This 582cid big-block is built on a high-strength Dart Big M Sportsman block with 4-bolt, ductile iron mains and a Hardcore Horsepower 4340-forged steel crankshaft with a 4.375-inch stroke. That's a bulletproof combination for a high horsepower N/A combination.
The AutoTec small dome pistons are custom-made from 4032-forged aluminum. Petralia feels 4032 aluminum is better for street engines than higher-end 2618 forgings. The pistons are sealed with 1.5mm Plasma Moly Top rings, 1.5mm cast iron 2nd rings, and standard tension 3.0mm oil rings from Total Seal.

Petralia then installed a stout rotating assembly including a 4-3/8-inch (4.375) stroke, 4340-foged steel crankshaft that was zero-balanced to run with a Neutral balance, (aka "Internal Balance"), harmonic dampener and flexplate or flywheel. Factory GM 454s and 502s were all external balanced, but many consider internal balancing an improvement so he likes to stick with that when he can.

The pistons are custom made slugs from AutoTec Pistons in Huntington Beach, CA. They're forged from 4032 aluminum with a small dome profile that gives this engine 10.85:1 compression. Which is fine on 93-octane unleaded when combined with the very efficient CNC-finished combustion chambers in the Air Flow Research heads. The slugs hang on 4340-forged steel rods with 7/16-inch ARP2000 capscrews. King Racing HP-series bearings cushion the blows.

The team at Hardcore Horsepower file-fits every set of piston rings for every engine they build using this precision ring grinder from Total Seal Piston Rings. File fitting piston rings has long been a staple of high performance and racing engine assembly. The goal is to minimize the leakage path through the ring gap to maintain maximum combustion pressure against the top of the piston. For many years engine builders used small files to perform this procedure, but as technology progressed they turned to sophisticated ring gap grinding tools that added a high measure of precision to their ring filing efforts.
Early in the build process, Petralia likes to do a rough check of the piston bore clearance. While he admits it's not an accurate as measuring the pistons and bores with a micrometer and dial-bore gauge, this quick and easy check verifies that the finished bore size is close to what's needed for the application. There's 2 feeler gauges stacked in this picture, a .0015+.0025=.0040, which the piston can just barely slip past. Min spec for this 4.600-inch bore, 4032-forged pistons for street use is between .004-.0045 so it's right on. The best part is anyone can do this check at home without buying expensive tools.
A Moroso fabricated steel oil pan and welded screen pickup feed oil into a Melling Select oil pump to fill all the blocks' passages with straight 30-wt Lucas break-in oil which keeps all the spinning metals from forming an unholy union while on the dyno. Synthetic 10W-30 oil will fulfill those duties once it's in the car, a '68 Camaro in this case. A Fel-Pro one-piece silicone pan gasket seals it all up.
This is the largest displacement BBC engine Petralia will build with a standard Chevrolet deck height, which makes it easier to fit under hoods. The 9.800-inch deck also fits practically all the muscle car headers on the market today. He said he could add a little more stroke and make 598cid if a customer really wanted it. But that limits connecting rod length which affects rod/stroke ratio. It would also shorten the piston compression height (the distance from the pin centerline to the flat, top surface of the piston). And the extra 16 cubes really wouldn't make that much more power either.
The small dome pistons installed at zero deck and, combined with AFR's 121cc chamber and 13.9cc Mr. Gasket head gaskets, give this engine 10.85:1 compression. That may seem a bit high to some, but AFR's CNC-ported combustion chamber is very efficient and can run a higher compression ratio than some other heads.
Behind that billet steel true double roller timing set with 9 crank key positions is Petralia's secret hydraulic roller grind. He won't share the specs, but says this cam is slightly modified from the last one he ran and that may have contributed to this engine's higher power.
Some customer's don't like the silver or gold finishes offered on today's high performance aftermarket oil pans. Petralia had this Moroso pan powder-coated black instead.

"The power potential is in the heads and cam"

Choosing the right cylinder head for the application is critical. But Petralia is secretive about his head selections, allowing only that they are CNC-ported castings from Air Flow Research. Runner volume is shared only with the customer. And sometimes not even then. He was willing reveal that the heads are rectangular port and came equipped from AFR with a modified spring package he specc'd out to work with the custom-ground hydraulic roller bump stick from Comp Cams. "It's basically the same cam I ran the last time, with a tweak to lobe sep angle, and a 4/7 firing order swap". As you've probably guessed by now, he won't share cam specs either except to say that it's just about .700-inch lift w/ a 1.7:1 rocker arm ratio.

Custom length pushrods are almost always needed when you combine this many different aftermarket pieces in one high performance build. Petralia always measures for the correct size. This is particularly important on big block Chevys because they use two different length pushrods.
Here's a reason Petralia says you should always clean out new pushrods. The set he ordered for this engine came from a top-name brand in the pushrod business. The cleaning brush wouldn't go through one pushrod and Petralia had to use a drill bit to clean it out. He has no idea what was stuck in there, but the other 15 pushrods were typically dirty, but not clogged like this one.
AFR's BBC heads use adjustable pushrod guide plates. They're a pain to set up, but really are the best way to locate the rocker tip over the valve. The set-up process is lengthy and tedious, and be sure to remember to torque the rockers studs down afterwards. Petralia also checks alignment after the engine's break-in cycle on the dyno and says he sometimes has to make minor adjustments. Note the yellow dots on all fasteners indicating they've been torqued to spec.
Big-block Chevy heads with big ports like these require the intake rocker arm studs be sealed to prevent oil from getting sucked into the runners. Petralia uses Black RTV Automotive-grade silicone to do the trick. He also checks each port carefully to ensure that the threaded stud base does not protrude into the port roof.

When installing aluminum roller rockers on big-block Chevy heads there are 2 rockers that will cause problems with some valve covers. This rocker arm set from Erson cams includes 2 rockers with added clearance just for these spots, which are the intake rockers for cylinder numbers 1 and 8. You can also see the rocker arm stud girdle made exclusively for AFR by Jomar Racing Products.


Since the block was decked to an even 9.800-inches, and extra-thick intake gasket was needed to align the bolt holes and seal the manifold. This Mr. Gasket Company gasket is .120-inch thick.
Petralia choose this single-plane aluminum intake manifold because it was the lowest one he could find that would fit a 4500-Dominator carb. It worked well right out of the box with no modifications making an initial 820hp and 780tq without a carb spacer.
The intake manifold was a surprise. "We were looking to gain the most hood clearance possible, and still be able to make big power with a 4500 Dominator carb". This intake from Speedmaster turned out to be the real deal. "On our flow bench it flowed about middle of the pack for BBC manifolds. So we were expecting to make middle of the pack power and torque numbers with it. Especially compared to some of the higher-dollar intakes we've run in the past". At only 5.88-inches tall, it's actually the shortest manifold in its class. But it rewarded them with 820hp after just some very minor tuning. Which was about 15 more hp than they were expecting. The even bigger surprise came after testing a few different carb spacers. "We were happy with 820hp, but wanted to know if there was a bit more left in it. So we bolted on some different carb spacers and proved that tall plenums really do contribute to more power". The engine woke up to 850hp when a tapered billet spacer was bolted on and a little more tuning added in.
The 582ci BBC also made over 800 ft/lbs of torque from 4800 to 5200rpm and never made less than 700 ft/lbs from 3400 to its 6000rpm redline. There's no need to rev this bad boy up. And it makes enough grunt to move any street car or truck into the stratosphere.
The engine responded even better once a carb spacer was added. Peaking best overall at 850hp and 808tq. And now at least the customer has options for hood clearance, even if it might be a little less powerful without a carb spacer.
You can see the massive amount of torque this BBC builds. Never dropping below 700 ft-lbs on this peak run. It cranked out 850hp at 5,900rpm and 808tq at 4,900rpm.
Petralia even did a lower-rpm "long pull". The big cam and Dominator carb didn't respond too well down below 3,000rpm, which is pretty typical during dyno testing. But this data shows the engine would work well with a 3,500rpm stall converter because it really kicked in, making above 700 ft-lbs at 3,400rpm and holding onto it 'til redline at 6,000. Peak numbers fell off slightly due to heat soak during this longer dyno pull, which is also a common occurance.
Who says big-blocks are too heavy! This engine weighs less than 560-lbs carb to pan as shown.
Petralia also attributes part of the power increase this engine made vs the last 582ci BBC he built to the new 2 1/8-inch Hooker headers he ran for the first time during this series of tests. He didn't do any back-to-back tests against smaller 2.0-inch headers he had used before, or any larger ones either. So there might still be some more left in this thing!


Mike Petralia's Hardcore Horsepower & Dyno

Franklin, TN 615.595.0060