Racing 4 Education

Combo 71.

Combo 71 comes from pages 84-94 the March 1998 issue of Super Chevy.

Combo 71 discusses a 383 cu. in. small block that makes 525 HP and 535 ft-lbs of torque. The engine has great heads, a very healthy street roller camshaft, and a stout bottom end. The camshaft has a lot of valve lift, with 0.614 in. of valve lift on the exhaust side and 0.592 in. on the intake. This engine is still very streetable—the compression ratio is only 9.4:1 and the heads only have 190 cc intake runners. With more of the racing treatment, this engine could have easily made over 650 HP. Of course, only street engines are shown here.

Combo 72.

Combos 72 and 73 come from pages 65-71 the February 2000 issue of Super Chevy. They use the same 350 cu. in. block and Speed Demon carb. These two combos compare GM #441 heads to GM L31 Vortec heads.

Combo 72 is the baseline engine for the test. An average-performance cam is used with the GM #441 heads to produce 324 HP and 363 ft lbs.

Combo 73.

Combo 73 replaces the #441 heads and Edelbrock Performer RPM intake with GM L31 Vortec heads and an Edelbrock Performer RPM Vortec intake. The Vortec-style intake is needed because the Vortec heads feature intake bolt-holes that are vertical and not angled. A more aggressive cam is used on this combo. Another notable difference is that the Vortecs have smaller combustion chambers, which up the compression about 1.5 points. These upgrades produce 375 HP and 408 ft-lbs of torque.

Combo 74.

Combos 74 and 75 come from pages 54-57 of the December 1999 issue of Popular Hot Rodding. These combos use a 355 cu. in. engine and compare the GM L98 Corvette heads of the late 1980's to Trick Flow Specialties' 23° street heads. Both engines are great street/strip engines.

Combo 74 uses the GM L98 Corvette heads that were offered from 1986 to 1992 on early-style small blocks. The L98's feature smaller 163 cc intake runners and 1.94/1.50 in. valves. These heads are run with a mid-performance camshaft to produce 380 HP and 386 ft-lbs. The torque peak of 386 ft-lbs occurs at 68% of the HP peak, which is a little low.