Lunati used "generic" 305 iron cylinder heads (casting number=14014416, used on LG4 and HO engines), replacing the 1.84-inch stock valves with larger 1.94-inch valves, but kept the stock 1.50-inch exhaust valve size, treating both to a "good' standard valve job. They also ended up gasket-matching the heads and doing a little bowl work before installing Lunati high-performance springs, retainers, locks, screw-in studs, and pushrod guideplates.

Lunati's engine was tested on Dynotech's SuperFlow dyno using a generic set of 1 5/8-inch primary tube headers. The best results were obtained with the stock jetting and 38 degrees total timing, where a peak of 343 corrected horsepower at 6250 rpm was observed. The peak torque output of 356.2 lb-ft occurred at 4250 rpm. The engine made over 1 hp/cubic inch from 4500 through 6500 rpm, the highest rpm tested. It made over 300 lb-ft of torque from 3000 rpm (the lowest test point) through 5750 rpm.

Through all the tests, the engine idled smoothly at 750 rpm. Dynotech's technicians believe the engine would have more potential with less restrictive heads. They also think that the engine would perform better with a 650- or even 700-cfm carb, albeit at the cost of additional bottom-end sogginess.

Racing gas with a 108-octane level was used for all tests. This gas is not generally available for street cars. Assuming the use of 92- or 93-octane unleaded, you could get by with a true 9:1 to 9.5:1 compression ratio street motor when using cast-iron heads. The generally accepted rule of thumb is that you lose 12 to 15 hp for each point drop in compression-- so an otherwise identical 9 1/4:1 engine would be down about 15 hp from the results reported here. This lost power could be easily regained by using aluminum heads fitted with bore-clearing 1.94/1.50 or 1.55 valves, such as those offered by GM or Air Flow Research. Not only do the heads flow much better than 305 iron castings, but aluminum's superior heat-rejection characteristics allow 10:1 street engines on available unleaded premium pump gas. In any event, the end result is a 305 that will surprise quite a few late-model 350 owners.