Excerpts from Forza October 2003 Issue (Number 48)

The Scientific Method

To find out what really improves engine power, you've got to make changes one by one, testing each on the dyno along the way. CAROBU Engineering applies the scientific method to get more power from a 308 GT4, while JAY JONES follows along.

...Casey and partner Bert Wehr (CAROBU's master engine builder and dyno man), rebuilt the 2-valve engine to OE spec so they could run it on the dyno and establish a baseline for performance. They retained all stock parts including the four-ring pistons and mainly "freshened" the top-end. All specs were retained, including the 8.8:1 compression ...

... a Tubi muffler was installed. It's a better-looking piece (in polished stainless steel) than the well-aged OE unit, but more importantly it offers a genuine improvement in exhaust flow. It's obvious at a glance that the Tubi has smoother transitions, and the dyno confirms its greater efficiency. Adding the Tubi improved horsepower and torque all across the curve, for a peak of 229.5 horsepower @ 6,700 rpm and 198.5 lb-ft of torque @ 5,600 rpm. Again, even though this does not seem like high overall peak horsepower, the Tubi muffler produced a broad overall increase, providing more low-end grunt and tractability throughout the rpm range...

...CAROBU's 21st century computerized dyno, which utilizes DTS 4000 software, would soon dispel any myths or disputes about the horsepower and torque figures of an early Euro-spec 308 engine. Once the test parameters (beginning and ending rpm, etc.), are programmed into the computer, the dyno is set into motion, its computer automatically feeding load onto the engine while it cycles through a specified test range. (Wehr's guiding hand assured that the power could be cut immediately if any hint of a problem developed.)...

...After that testing, the engine will be extracted once again to move onto Phase 2, going into the internals of the engine for even more street performance. Expect modifications to the intake ports, camshafts and a realistic compression ratio somewhere between the OE 8.8:1 and the racing 12.0:1. Instead of the mythical 300-hp 308 motor, we can expect a reliable, great-running street engine in the more realistic 260 to 280 horsepower range. The performance such an engine can provide will certainly make for an enjoyable car, and we look forward to recording it. Watch for a future installment on this CAROBU 308 makeover...