Hot Rod Magazine builds a 400hp 305
The process began with an ordinary 9.5:1 short-block (L69) as delivered from Chevrolet. To this package they added a hydraulic camshaft from Competition Cams' High Energy Magnum series and the attending valve springs and retainers. The cam is a CS292-H-10 that features 244° duration at .050" lift, 110° lobe centers, and .501" net lift on each valve. Crane Cams made up some .100" shorter pushrods to correct a slight rocker arm geometry problem; however, they probably wouldn't be necessary in every case. The cylinder heads are from RHS (Racing Head Service)and they sport Manley Pro Flo valves and a mild porting job.
Then they added an Edelbrock Victor,Jr. intake manifold and a modified 650-cfm Holley double-pumper carb. Hooker's 1¾" primary tubes headers were connected to a pair of Supreme Super C turbo mufflers. They already had an MSD-6A ignition amplifier in the car, and it was wired into one of Autotronic Controls' new MSD Extra Duty distributors. A 4" tall K&N air filter was attached to the carburetor. Everyone involved was surprised at the amount of power and the degree of driveability the package displayed.
Dyno Test Results
All of these modifications can be made to your stock 305 without ever removing it from your car, and they will provide similiar, but somewhat lesser, results when applied to the more common 8.6:1 LG4 305, 4-barrel combination. The compression ratio on this engine approached 10.6:1 when actually measured, and while we haven't physically checked an LG4 engine, we feel safe in saying that similiar modifications would yield a very driveable engine with better than 9.0:1 compression. This may seem like a bit too much cam for a small engine, and a Victor,Jr. intake manifold also seems out of line, but the engine is really responsive to the combination.
The best thing is that you can approach it in stages; each step adding a little more power without compromising the overall package. We suggest you work with the exhaust system first and then move on to the head work before installing the camshaft and manifold combination. But you can really do it any way you like and still get impressive results.
In early testing, the Z28 has already run 106 mph in the 13 second bracket, and we look forward to plenty more before we're finished. Now, of course, all these modifications are totally illegal if you drive your Camaro on the street, but they're the only things that make sense.