496 Short Block Top End Engine Build - Ground & Pound
Building The Ultimate 496 Boulevard-Brawler
From the October, 2009 issue of Chevy High Performance
By Sean Haggai
Photography by Sean Haggai
Your street motor should share many of the characteristics of an MMA or UFC opponent, whether it's for the local cruise, the all-out open drag nights at the track, or even the everyday haul. And you can get the job done with off-the-shelf components. The days of super-custom engine builds with race-gas compression are all but gone in the today's street cars. Virtually every part is available over the counter, which brings the cost down, making such an engine build that much more realistic. Having the opportunity to tag along on an engine build, we wanted to illustrate how easy it is to make gobs of power.
As you may have already guessed, this isn't your average 454. In fact, it's an even larger 496 with a pump-gas-friendly 10.25:1 compression. While other options could have us wringing out a short-stroke small-block till all ends of the rev band, an easier option was to piece together an existing 496 short-block for the Bel Air we had in mind. Not only will the motor live longer with fewer revs, but it will have the benefit of more inches, and power will be on tap virtually everywhere in the rpm band.
Now, with any street-specific motor build, certain perimeters must be met. It has to be easy on the budget, must run on pump gas, and must produce useable twisting actions without wringing the pumper out of breath to do so. Plus, ours had to fit under the stock hood of a very clean '66 Bel Air. All in all, when you can get it to look exactly like the factory 425hp 396 big-block it came with as a factory option, kudos to you.
We met up with John Barkley and whipped up a ground-pounding, 600-lb-ft big-block factory lookalike out of his garage. We began with an original GM four-bolt main block, an Eagle rotating assembly with a 4340 steel crank, SRP pistons and rings, a Melling oil pump, and a Moroso pan-with ARP bolts throughout. It also has the benefit of a pair of large aluminum 320cc lungs from RHS, a complete Comp Cams valvetrain with a Thumpr hydraulic roller camshaft, and lifters to boot. We even utilized faux intake bolts, making the Weiand Stealth manifold look factory. In true CHP fashion we strapped the big-block on the engine dyno at Vrbancic Racing in Ontario, California, and put the 496 through its paces. And now here's an easy-to-reproduce recipe, should you want to whip up this combination yourself.
Churn out 570 hp and 600 lb-ft from our RHS-headed 496
With a diesel-like torque curve, it's the perfect motor for the street
Our build primarily consisted...
Our build primarily consisted of adding a competent top end to satisfy the bottom. The block is a factory GM four-bolt with steel caps; however, the bore was punched 0.060 over, making it 4.310 inches.
To keep the compression low...
To keep the compression low but still take advantage of the squeeze, the deep holes were filled with domed, paint-can-sized 4.310-inch SRP forged pistons. Underneath, our crank was an Eagle 4.250-inch 4340 forged steel piece with 2.750-inch main and 2.200-inch rod journals. To handle the pounding, we used a full set of 6.385-inch H-beam rods with ARP rod bolts. For sufficient oil, we called on a Melling pump and pick-up. Our factory-style pump would allow for our Moroso oil pan to fit with clearance.
Before the RHS cylinder heads...
Before the RHS cylinder heads went on, we installed our Fel-Pro 4.580-inch-bore head gasket set, which features a wire-ring combustion seat with stainless steel for extra sealing. They are also made with a solid steel core to minimize torque loss and gasket blowout so the clamping force is maintained.
Breathe Deep Don't let the...
Don't let the orange paint fool you. These are fresh-out-of-the-box aluminum Pro Action 24-degree cylinder heads from RHS. They came complete with hardened seats and bronze valve guides. The intake valves are 2.250 inches, and exhaust valves come in at 1.880 inches (11/32-inch diameter for both). They also come with dual 1.509-inch valvesprings, 3/8-inch guideplates, and 7/16-inch rocker arm studs.
To fasten the cylinder heads...
To fasten the cylinder heads down, following the instructions from ARP, we installed the head-bolt kit. We torqued each 12-point head bolt in a clockwise pattern, starting from the center and working our way out with moly-lube on the threads and oil on the washers. We torqued each to 85 ft-lb, and let them sit for 10 minutes. We then backed off a quarter-turn and retorqued each bolt in the same clockwise pattern.
In some cases the pushrod...
In some cases the pushrod guideplates will have to be clearanced. Our situation called for relieving the outer edges of some plates to install the ARP 12-point head bolts.
1. Wilson 1-inch tapered spacer. The Black anodized piece straightens out and helps atomize the fuel before it reaches the chambers. An affordable way to free up those last few ponies.
2. Cylinder heads are RHS 320cc aluminum pieces. Each comes complete out of the box for $1,020. Exhaust ports are raised 0.500 inch and come predrilled for front accessories.
3. Straight from the box with almost no jetting, the carburetor performed flawlessly. While the carb came with 79/79 primary/secondary jets, we ended up only jetting the secondaries to an 81.
4. Pertronix billet distributor with Flame-Thrower II ignition coil. If you already know what kind of motor you're running, call Pertronix ahead of time to set up a custom distributor curve.
5. Set of eight Zex spark plugs. Their heat range kept our big-block happy on the dyno, which meant there was no detonation or knocking. These feature a 0.708-inch reach and three electrodes for better spark distribution.
6. YearOne tall chrome valve covers for '65-87 big-blocks. While they appear stock, they're actually 1/2-inch taller to accommodate the use of roller rockers. They don't have the slant for power brakes, either.
With the heads on, we slid...
With the heads on, we slid in our Thumpr cam from Comp, chosen for its 2,500- to 6,100-rpm operating range. Not only would the motor make great bottom-end grunt, but with the amount of intake and exhaust valve overlap we could harness that great muscle-car idle. Our cam came with 243/257 degrees of duration at 0.050 and 0.570/0.554-inch lift (intake/exhaust). We lubed up the cam and, using a cam installer, locked it in, making sure not to ding the bearings.
For ease of maintenance on...
For ease of maintenance on the street, we also selected a set of Comp hydraulic roller lifters, since these lifters work specifically with newly designed roller cams. With an 0.842-inch outside diameter, they fit our stock lifter bores perfectly. We soaked them overnight in a tub of 30W motor oil.
Next we installed the lower...
Next we installed the lower timing gear and upper cam gear with the double-roller chain. We lined up the dowel pin on the cam shaft and set it in place.
With the cam in, we could...
With the cam in, we could adjust for thrust. Barkley derived a failproof method for measuring for cam thrust with a piece of duct tape since these timing covers have no hole for a dial indicator. The thickness of the duct tape is a perfect budget-indicator for determining the exact measurement since it is about 0.030-0.040 inch thick. With the tape on, we bolted the cover and found a perfect indentation imbedded in the tape surface. Our cam had correct thrust, and we peeled the tape to bolt the cover for final.
Designed for street performance...
Designed for street performance machines running up to a 4.250-inch stroke that see occasional strip use, these Moroso oil pans are modified with deep sumps. Under hard acceleration oil control is a must, so these pans are baffled and hold up to 6 quarts of oil, which is 8 inches deep. A crank scraper and windage tray are also included. They feature a passenger-side dipstick. With simple bolt-on installation into most production chassis, these Moroso street/strip oil pans are perfect for your weekend warrior.
Due to the cup height on our...
Due to the cup height on our hydraulic rollers, our pushrods were a bit shorter than usual. We ordered a set of Comp 8.100/9.100-inch intake/exhaust pushrods with a 5/16-inch diameter. We applied a bit of assembly lube to each end before installing them into the block.
When it comes to the valvetrain,...
When it comes to the valvetrain, Comp has it. To complement our camshaft and lifters, we added a set of 1.7:1 Ultra Gold rockers. These are not CNC-machined, but they are recessed for spring diameters up to 1.650 inches. We installed them on each 7/16-inch rocker stud and fastened them with a poly-lock and a 5/8-inch wrench. Note: Cylinders 3 and 6 require the "notched-corner" rocker arm to clear the inside of the valve cover.
We laid down the Fel-Pro one-piece...
We laid down the Fel-Pro one-piece oil pan gasket and applied a layer of silicone on top. Then we locked down each oil pan bolt with a 5/16-inch socket.
Our Weiand Stealth intake...
Our Weiand Stealth intake manifold was a perfect match. The dual-plane configuration has an operating range from idle to 6,800 rpm, and it's less than 200 bucks, which is a hard deal to beat. We laid down the Fel-Pro intake gasket then planted the manifold on top. We then installed the intake bolts and tightened them snuggly with a 9/16-inch wrench.
Next we installed our Pertronix...
Next we installed our Pertronix billet distributor and Flame-Thrower II ignition coil. We chose the simple Pertronix unit because of its ease of use. If for any reason we were stranded on the side of the road, parts for this distributor could be had at almost any auto parts store.
To supply the big-block with...
To supply the big-block with sufficient fuel, we topped it off with a Holley 950 HP. Updates include cast main bodies without choke horns, and smoothed venturi transitions for increased airflow. Other important modifications for the HP line include: screw-in air bleeds, stainless steel throttle plates, and notched floats. They also have Dominator-style fuel bowls to allow fuel line plumbing from either side.
|THE RUNDOWN |
|Combustion chamber volume ||112 cc |
|Intake runner volume ||320 cc |
|Exhaust runner volume ||135 cc |
|Intake port ||Rectangular |
|Spark plug ||Angle |
|Intake valve ||2.250 in. |
|Exhaust ||1.880 in. |
|Max. valve lift ||0.600 in. |
|Springs ||Dual 1.509 in. |
|THE SHOPPING CART |
|MFG ||DESCRIPTION ||PN ||COST |
|ARP ||12-pt cylinder head bolts ||135-3703 ||$92 |
|Comp Cams ||Thumpr hydraulic roller camshaft ||11-602-8 ||264 |
|Hydraulic roller lifters ||854-16 ||432 |
|Ultra-Gold 1.7:1 roller rockers ||19021-16 ||273 |
|Magnum pushrods ||7663-16 ||117 |
|Fel Pro ||Intake gasket ||1211S-3 ||33 |
|Oil pan gasket ||Z1884R ||38 |
|Head gasket ||1075 ||80 |
|Holley ||4150HP 950 cfm ||0-80496-1 ||715 |
|Moroso ||Big-block oil pan ||20403 ||248 |
|Pertronix ||Billet distributor ||D100700 ||230 |
|Flame-Thrower II coil ||45011 ||34 |
|RHS ||Pro Action 24 aluminum cylinder heads, complete ||11001-02 ||2,040 |
|TCI ||Rattler front balancer ||870006 ||384 |
|Transdapt ||Big-block timing cover ||9914 ||37 |
|Vrbancic Bros. Racing ||Dyno test and tune ||N/A ||500 |
|Weiand ||Stealth dual-plane manifold ||8018 ||197 |
|Wilson ||1-in. tapered 4-hole spacer ||004110 ||128 |
|YearOne ||Reproduction 396 valve covers ||NP503T ||56 |
|Zex ||Spark plugs, set of 8 ||82003-8 ||53 |
| ||TOTAL ||$5,951 |
|Fuel ||91 octane |
|Timing ||36 |
|Jets ||79/81 |
|Spacer ||Wilson 1-inch |
|Max. horsepower ||570 |
|Average horsepower ||471 |
|Max. torque ||600 |
|Average torque ||583 |