The 305 cubic inch small block Chevy has enjoyed a strange fascination within certain hot rodding circles and more of a loyal following than many are ready to admit. Some "knowledgeable" people will tell you that a 305 can't make any appreciable street power, they'll tell you that you can't ever do anything serious with any engine as small as a 305. I tend to approach life differently than other people, instead of asking what a motor can't do, instead I ask what a motor can do. Quite often, it is the smallest engines which give up the biggest gains in performance. In all honesty, can you do anything with a 305 small block Chevy? Yes, you can do plenty with the 305 small block Chevy and you can do it cheaply and easily. One of the best examples of this particular motor is the engine designated as the L03. The L03 engine, mostly found in the 1988 to 1992 Third Generation F-body Camaro and Firebird models, but also in certain other GM cars and light trucks, makes an excellent hot rodding project because it is plentiful, affordable, and offers a wide range of modification possibilities.

But why choose a 305 to modify instead of the much more popular 350? People are quick to forget the 265cid and 283cid small block Chevy engines that eventually led to other engines like the 350. People forget the awesome 6000rpm plus 302cid V8 of the '67 to '69 Camaro Z-28, itself a 327 destroked with a 283 crankshaft. 302 cubic inches? In an era of high performance engines with much larger displacements, the 302 was just too small ! However, its small displacement didn't stop the high winding Chevy 302 from becoming a legend in its own right.

No. The small 305 became unpopular mainly due to reasons other than just its small displacement, most of these reasons being the product of pure ignorance and hear-say among so called 'professionals' who acted like anything but...


The electronic throttle-body injection assembly found on the model year 1988 to 1992 5.0 liter L03 305cid V8 motor is a Rochester Products Division Model 220 series TBI unit. The Model 220 is equipped with twin Multec fuel injectors each with a 43mm, 1.693-inch bore. The injectors are mounted above the butterfly-like throttle body assembly. The injectors are current-technology, ball-seal-type units that deliver fuel at a maximum rate of 54lbs per hour (24.5kg) at a conservative 10-psi fuel supply pressure. Engine idle speed is controlled with a simple pintle driven by an ECM-controlled stepper motor in the throttle bypass air circuit. The system continuously self-adjusts for all air density variations and engine load parameters as the ECM moves the idle air control pintle in or out the correct amount required to maintain the proper idle RPM. A special idle air passage in the throttle body assembly itself distributes air evenly to both sides of the engine, resulting in improved idle quality and low-speed drivability. A variety of sensors placed around the unit and the motor itself provide the ECM the input necessary to adjust the engine operating parameters.

It sounds complicated, but TBI is actually easier to work on than a carburetor, and a lot more efficient.


TBI has been (somewhat wrongly) termed a 'smart carburetor'. It is 'that', and much more. TBI is digital / electronic fuel injection system that utilizes the traditional wet manifold design. TBI shares the wet manifold design with the long aging carburetor, among a few other similarities, but TBI is not a 'smart carburetor'. If I were to refer to TBI in comparison to the intelligence level of a carburetor, 'smart' would be an insult. Adjectives like 'Brilliant' and 'Genius' would be more appropriate than just 'smart'. In comparison to TBI, the typical carburetor does well to reach the descriptive adjective of 'retarded' in comparison. TBI is highly capable, precision computer controlled and adjusted fuel injection, and differs from TPI only in how the fuel is introduced to the cylinders. TBI sprays fuel into the intake manifold, under high pressure and in precise amounts according to data taken from numerous sensors in and around the engine, all controlled from a dedicated engine management computer termed the ECM by GM. This fuel spray is mixed precisely with a carefully determined amount of air at the point of entry, whipped through the intake manifold by engine vacuum and distributed to each cylinder by air flow and vacuum routing.

Sound like a carb to you?

Not quite. A carb relies on highly inaccurate and often inconsistent engine generated vacuum to feed and mix the fuel properly. Very inefficient and unpredictable and when compared to the computer controlled injection systems, very primitive. EFI is the future and the carburetor is the past. There are many reasons no American car is produced with a carburetor. Those reasons include; drivability, economy, efficiency, power, reliability, and throttle response. All very good reasons. A carburetor just can't compete with EFI, not in the light of educated argument and real world performance.

Here's what the GM techs said about TBI:

"Everybody figured throttle body injection wouldn't fly because it was nothing more than a force-fed carburetor. When you run it on the dynamometer it doesn't look like anything. When you measure the various parameters such as mixture distribution and brake-specific fuel consumption, it doesn't look like anything. But, when you put it against the best emission controlled carburetor we had in 1979, '80, and '81, the car drove worlds better with Throttle body fuel injection. It translates to something that's measurable in car fuel economy and drivability and the customers love it."

Now that we have described the various induction systems, let's talk about manifold designs and induction operations.