Those ovals were all we had back in the '70s and early '80s, until the oval aluminum heads came along. Yes, the closed chamber did close off the intake side of the chamber, but that 97cc chamber makes it very easy to build compression. What I would recommend is installing 1.88-inch exhaust valves in the cylinder heads, opening the throat on the exhaust side to 86 percent of the valve size, and cleaning up the bowls on both the intake and exhaust. Leave the standard 2.07-inch intake valve. If you go to the larger valve, it will only be shrouded by the chamber walls. A good bowl job will help the flow and get you where you want to be for power.
The Comp Cams 280H is a good selection for the power range you are trying to reach. The Magnum camshaft series has been out for quite some time. The newer Xtream Energy line has more current technology in lobe design. The valve speed has been pushed to the max, with power benefits to be reaped. I would recommend going with the XE274H. Another thing I like is the Xtream Energy camshaft, a dual-pattern cam with 6 degrees more duration on the exhaust side. We're back to getting that exhaust out and aiding the intake side by having low pressure during the overlap. The camshaft specs out at 230/236 at 0.050 inch tappet lift, 0.552/0.555 inch max lift, and is ground on 110 centers.
You see it all the time: Too big of a primary pipe on engines. They're giving away too much slow-speed and peak torque just to gain a few horsepower at the very top where you don't drive very much. For your engine package, I wouldn't run any larger than a 171/48-inch primary pipe, around 32-34 inches long, with a 3-inch collector. As for the exhaust system, I would recommend going with a 211/42-inch dual system. While many people love X-pipes, some don't like that high-pitched exhaust note they give you. A properly designed H-pipe or balance pipe will give you the same performance as an X. The only problem is that the crossover needs to be the same size as the exhaust system (211/42-inch) and be placed right at the end of collector. This will equalize the pressure imbalance caused by two cylinders firing 90 degrees from each other on the same bank of the engine. Flowmaster has what it calls a Scavenger Cross Over pipe. This crossover is very similar to an X-pipe, but Flowmaster uses its patented D-port technology to help scavenge the exhaust from side to side of the engine. As for mufflers, everyone has good performance mufflers. Borla, Dynomax, Flowmaster, and Magnaflow each have good street-performance mufflers. Check with your manufacturer of choice for its recommendation based on the sound you're looking for.
Fine-Tuned Damper QI have a '95 Corvette with an LT1. Before I replaced the stock crank pulley with an ASP underdrive pulley, I noticed that the stock pulley had one pin in one of the balancing holes. Now I'm afraid that the crankshaft is out of balance. Timo RajataloRovaniemi, Finland
A Yes, the damper on your LT1 is zero balanced. This means that it doesn't have any additional counterweights built into the damper to balance the rotating assembly. Now, the flexplate or flywheel on your engine does have a counterbalance weight built into it. When GM went to the one-piece rear main seal they lost the small counterweight on the flywheel flange of the crank. The holes you're referring to in the damper pulley are for fine-tuning the balance on the assembly line. GM fires up the engine while it's hanging from a chain fall as the engine is going down the line. They fire the engines on propane and run them up, check for oil leaks, and dynamically balance the engine with very slight weights. We wouldn't be worried about one pin in the stock damper pulley. We've seen up to three pins in other engines.