Corvette Engine Build - The Power Principal, Part 2

We continue with our Econo 383 build

Chris Petris Dec 7, 2009 0 Comment(s)
Corp_0706_05_z Corvette_383_engine_build 1/28

Now we check our cam timing by checking as the intake starts to rise and then before it returns to the base circle of the cam. We could use up a few pages just on cam timing and the theory behind it. Contacting Comp Cams and ordering their video on the procedure that walks you through the entire process is the best policy. One more thing-if you change the cam timing, recheck the connecting-rod-to-cam-lobe clearance. The cam lobes can be closer to the connecting rods when cam-timing changes are made.

The stock tuned-port induction system that produces great low-end torque but severely restricts high-rpm horsepower was previously replaced with an Accel SupeRam plenum and runner kit intake-manifold assembly. The large SupeRam plenum provides low-end torque, and the shortened, large-diameter runners allow high-rpm breathing. We dumped the '85 Corvette fuel-control system and went with the FAST bank-to-bank, fuel/igniton, computer-control system to get as much power and low-speed drivability as possible. Laptop tuning makes the system very user friendly, and the computer's operating speed is greatly enhanced over the OE '85 system.

A key component when adding any induction system is figuring out the proper fuel-injector flow rate so we don't lean out the engine at high-rpm and have a meltdown. Having too much fuel is not as catastrophic, but low-speed drivability and throttle response would suffer. High-rpm performance wouldn't suffer, but you have to get there, and unless you're driving there all the time, fuel efficiency would be terrible. RC Fuel Injection has a great web site (www.rceng.com) that has the formulas necessary to size the injectors correctly. When we loaded our desired 475 crankshaft horsepower, number of injectors (8), 50-psi fuel-rail pressure, 0.80 injector duty cycle, and our 0.47 brake-specific fuel consumption desired, our combination required 32 lb/hr or 320cc/min injector flow. This flow rate addresses wide-open throttle performance which will be limited to short intervals. With this info, we then decided on 30-lb/hr fuel injectors to keep the throttle response crisp. If we planned on running a long-distance, wide-open throttle race, we could increase our fuel pressure to 75 psi, giving us plenty of fuel at top end.

The next question that needs to be answered is what injectors do we buy? Aftermarket Bosch clone injectors are reasonably priced, so we got a set of 30 lb/hr and sent them to Cruzin Performance for a quick injector performance test to be sure of equal fuel delivery to each cylinder. The results weren't good: 12-percent flow differential and one injector cap was leaking fuel already, and the injectors were never run in an engine. We opted to try a fresh set of Bosch EV 1 fuel injectors, and the results were much better: 2-percent flow differential and no leaks. Using the original Bosch injectors cost more up front, but the engine and engine compartment will not suffer from smoke inhalation or shrapnel.

The only ingredient left is the ignition system. We used the Performance Distributors Mini VIP voltage step-up regulator that boosts system voltage to the precision-built Performance Distributors computer-controlled distributor. Their Mini VIP step-up voltage regulator will boost our coil voltage to 18 volts under high-rpm to light our Bosch Platinum Plus Four spark plugs with ease. We're glad we have the Performance Distributors Live Wires to keep all the voltage contained. One wrong touch with an inferior set of wires, and we'd be knocked to the ground

You'll notice from our photos that we have the engine installed less the intake and distributor. Since we had to run some additional wiring under the intake, this was the easiest way to assemble the complete engine.

All that's left now is the dyno run. Stay tuned!

COMMENTS

TO TOP