Big-Block Chevy Horsepower
Q: I have a ’69 Chevelle SS with a ’72 454 Chevy big-block engine that has been bored 0.030 inch over. The stock crank has been turned 10/10 on the journals, and I have reconditioned stock rods with ARP bolts. The pistons are TRW L2465F forged domed. All of this has been balanced for smooth operation. The cast-iron heads were ported and gasket-matched, and I had stainless steel 2.19 intake and 1.88 exhaust valves installed. The block has been decked and the heads have been shaved to 115cc to achieve a compression ratio of 10.25:1. The camshaft is a hydraulic flat-tappet Lunati special purpose grind PN H225-235 with stock rocker arms. The intake is a Weiand Stealth with a Barry Grant 750-cfm Speed Demon carburetor. The distributor is an ACCEL 52000 series with the 300+ ACCEL digital box and matching coil. Hooker Super Comp headers reduced down to 2.50-inch exhaust flowing through Flowmaster 40-series mufflers and 2 1/4-inch tail pipes in stock location with chrome tips. The Muncie four-speed transmission has a 3.55 posi 12-bolt rearend. It’s on 26-inch tires, and the engine has about 10,000-15,000 miles on it. This combination has a lot of power and I’m assuming it produces over 400 hp, but you know how it is when the horsepower bug bites you; I want more power. This car is a weekend warrior and usually gets 110-octane race gas.
I now have the funds for aluminum heads, roller camshaft, lifters, and roller rocker arms. I was thinking of purchasing the Edelbrock RPM Performer (PN 60459 or GM PN 12363390) heads and a COMP Cams roller camshaft and lifters along with COMP Ultra Pro Magnum roller rocker arms. Will I have any problems with the Edelbrock or GM heads and the pistons that I currently have in the engine? Would you recommend different heads than the ones I have chosen? What camshaft would you recommend? Would a hydraulic roller be better than a solid roller? What kind of distributor gear should I get for my ACCEL distributor? I would like to break the 500hp mark with a naturally aspirated engine, if that is possible with what I have. This is not a daily driver, and fuel economy is not a concern. I have subscribed to your magazine for more than 10 years and enjoy reading all of the tech tips and articles about making more horsepower. Any help you can provide me will be greatly appreciated. You have an excellent magazine; keep up the great work!
A: Isn’t this horsepower thing a real addiction? If it makes you feel any better, you’re not alone!
Your plan does have a few issues. Both the GM Performance Parts and Edelbrock cylinder heads are a semi-open chamber design, which will crash into your full-open-chamber TRW piston domes. If you wish to switch to aftermarket aluminum heads, you’ll need to go with an open-chamber design. We really like the Dart CNC Pro-1s, but this may be a little too much cylinder head for your build. Dart also offers a new Pro-1 oval-port 275cc inlet port aluminum head. These feature a 121cc open combustion chamber that can be milled down to a minimum 108cc combustion chamber volume. If you clip the heads 0.030 inch you’ll be right back to your 115cc pump-gas friendly 10.2:1 CR. The heads (PN 19000171) come completely assembled with 2.19-/1.88-inch stainless valves and 1.550-inch single valvesprings with 145 pounds on the seat and a max lift of 0.660 inch.