Taking advantage of GM’s unique CRC factory roller program, Patterson Racing built a 2014 COPO Camaro clone from the ground up and applied many of the tricks learned in Comp and Pro Stock to the 396ci naturally aspirated LS3-based engine.
Why build a COPO engine to stock specs from scratch when such a powerplant is available as a crate engine from GM?
To go faster, that’s why.
“In Stock Eliminator, everyone has to use the same parts. So, how do you make yours better than the next guy?” asks Todd Patterson, who along with father Allan have prepped and raced six COPO Camaros since the program’s introduction in 2012. “Well, you go to extremes in blueprinting.”
To see just how much power can be gained from blueprinting, check out the dyno results at the end of the story!
Following the rules
Engine-building rules under the NHRA Stock Eliminator are strict, so precise blueprinting and other assembly strategies are important to gain an edge on the competition.
This is where some of the Pro Stock and Comp Eliminator technology funnels over. – Todd Patterson, Patterson Racing
Patterson’s customer wanted to take up NHRA Stock Eliminator and run a 2014 COPO Camaro. Of course, GM builds only 69 COPO cars a year, and securing one of the limited-edition models is a tough if not expensive choice.
Upwards of 2,000 potential buyers show interest in getting one of the production COPO cars, and they cost in the neighborhood of $110,000. However, there is another option: the Camaro Rolling Chassis program.
Inside the Camaro Rolling Chassis
Set up to serve grassroots drag racers, the CRC program provides the customer a rolling Gen V Camaro chassis set up identically to a COPO car but without the drivetrain. The car is fully painted, features a complete interior, boasts a race-ready fuel cell and 4-link rear suspension, and comes with a certified 8.50 rollcage. Cost is about $60,000. Customers then choose which engine and transmission they want for the car and finish the build. If the powertrain is built according to NHRA specs, the car is eligible for Stock Eliminator. The class depends on the weight and engine selection.
For 2013, 20 CRC cars were offered. You may have seen one of the cars built on the Gas Monkey Garage television show. For 2014, 17 cars were built, and this #10 unit obtained by Patterson Racing is the only one painted Victory Red.
All factory COPO engines are built at the GM Performance Build Center, formerly at Wixom, Michigan, and now moving to Bowling Green, Kentucky. Four engines were offered in the 2014 COPO Camaro: LS7-based 427 (NHRA-rated 430 horsepower), LS3-based 350 (350 horsepower), LS3-based 396 (390 horsepower) and supercharged LSX/LS7-based 350 (530 horsepower).
Patterson Racing leveraged its experience in Comp and Super Stock racing to build the 396ci naturally aspirated version and back it with a manual transmission.
“My father Allan studied the class structure and was intrigued with the 396,” explains Patterson. “Unlike most of the other COPOs, it’s a manual transmission. The owner last raced in the ‘70s in Modified Eliminator, and back in the good ‘ole days everyone ran a stick shift. That’s all he ever raced.”
Building the foundation
The 396 starts out with an aluminum LS3 block that Patterson cleans, deburrs and bores out to accept Darton iron sleeves.
Critical Part Numbers
- Block: GM 12621767
- Pistons: Diamond 80056
- Cylinder heads: GM 12629063
- Intake manifold: Holley 701R223B
- Throttle body: GM 19301616
- Fuel injectors: GM 12576341
- Coil packs: MSD 82878
- Oil pan: Stef’s 1025
- Oil pump: Patterson 151
- Piston rings: Total Seal
- Camshaft: Bullet
- Crankshaft: Callies
- Connecting rods: Callies
- Rocker arms: GM
- Valve springs: PAC
- Damper: ATI
- Lifters: GM
- Timing set: Cloyes
- Pushrods: Trend
- Fasteners: ARP
- Bearings: Clevite
- Head gaskets: Cometic
- Cylinder sleeves: Darton
- Bellhousing: Browell
New to the Patterson shop is a Rottler HP7A honing machine that uses diamond cutters in place of traditional abrasive stones. It also features a water-based coolant to keep the cylinder surface temperature down and help prevent warping the metal.
“The diamond cutters are harder than the surface they’re cutting, so they don’t wear out,” says Patterson. “Your consistency levels are much better.”
The factory COPO engine uses a 3.825-inch stroke Callies 5140 Compstar crankshaft, 6.200-inch long Callies 4340 H-beam Ultra rods and Mahle forged 4032 coated flat-top pistons. Patterson stayed with the Callies gear but switched to NHRA-approved Diamond pistons and Total Seal rings.
The NHRA allows an extra .015-inch on the crank stroke, so Patterson index grinds the crank for a 3.838-inch stroke, giving the engine a total displacement of 415ci. The crankshaft cannot be reshaped or lightened; however, some technology is allowed in getting past the required piston design.
Getting sneaky with the rings
“The factory piston grooves are .043, .043 and 3mm,” says Patterson. “You’re not allowed to alter the spec of the groove but you are allowed to run any ring in that groove.”
Patterson called on Total Seal for .027-inch top and second rings that are held in place with an .016-inch groove spacer. The top spacer is also cut with eight side gas ports while the second spacer is there just to take up width in the groove.
“This is where some of the Pro Stock and Comp Eliminator technology funnels over,” says Patterson.
Lubrication is handled with a Patterson Racing Products LS oil pump and NHRA-approved 5-quart Stef’s oil pan. Rounding out the short block are a custom Bullet camshaft, Cloyes timing set, Clevite bearings, ARP fasteners, ATI damper, Meziere water pump and Cometic MLS head gaskets.
Out-of-the-box cylinder heads
The LS3 cylinder heads must be run as cast with the exception of any valve job. The intake ports are set at 265cc and the exhaust ports are at 88cc. Minimum combustion chamber volume is 68cc. Stock compression ratio is 10.4:1, so Patterson will run as close as possible to the allowable specs.
“It’s a pretty good head right out of the box,” says Patterson. “Small-block guys 30 years ago would have killed to have 2.165 and 1.590 valves.
“Maximum lift at the valves is .605/.605,” says Patterson, “but we can play with duration and ramp design to ‘loft’ the valve a little. Also, we modified the GM hydraulic roller lifter to reduce the internal collapse and make it more of a solid lifter.”
“A couple years back we found a couple horsepower in the MSD coilpacks over the factory ones,” says Patterson. “Just like anything else, two here, two there and the next thing you know you’ve found 10 horsepower. When you have a spec engine, you have to take advantage of every little area you can to get a better result.”
Careful checking of tolerances is addressed to the exterior of the engine. Bellhousing alignment was found to be a few thou off, so offset dowels were required.
“We know from past experience it’s very critical that the bellhousing is zeroed in to the back of the crankshaft,” says Patterson. “If not, you can run the risk of pilot bearing issues or possibly messing up the thrust on the crankshaft. You don’t want to take anything for granted starting with a mass produced block.”
The 2-inch diameter, 30-inch long headers are specific to the COPO Camaro. Patterson will install O2 bungs for each tube for testing on the SuperFlow dyno with the Holley HP ECU and Sunoco Supreme 112-octane fuel.
“It gives you a true picture on the dyno,” adds Patterson. “We’ll see if a cylinder runs richer or leaner and it allows us to tune each cylinder.”
After the engine was installed along with a G-Force 5R transmission, the Camaro was taken to Tulsa Raceway Park for shakedown runs in FS/E trim, which has an index of 11.20 and a weight with driver at 3,360 pounds. With Patterson behind the wheel, the first full pass resulted in a 9.52.
“This car has the potential to be bad fast,” sums up Patterson.