Your Car Engine Help-www.auto-engine-parts007.com

Gavyn Linton, via CarCraft.com: I like cake. I like to eat it, too. And I like cool musclecars. With the price of gas currently north of $1.10 a liter and as high as $1.29/liter (that's roughly $4.65/gallon in U.S. dollars) I can't afford to drive my '72 Nova or my truck much. So, I challenge you guys to build a daily-driver musclecar with a V-8 that has a modest 300 hp and gets 30 mpg on regular pump gas. Anything goes. Gas prices will never go down, so we'd better figure out how we can keep these things on the street. Is this too tough to do?

Here is a 5.3L all-aluminum motor out of an SSR truck that Lingenfelter Performance Engineering (LPE) built in the Oct. and Nov. '04 issues. This little screamer made 378 hp with a 206-at-0.050-inch tappet lift and 0.571-inch intake lift hydraulic roller cam. This was with stock heads, stock 5.3L intake, headers, and the cam. With ported heads and a bigger cam, the motor made as much as 458 hp.

Jeff Smith: I love it when the readers challenge us, especially when the goal is at least realistic. From your e-mail, we'll assume you're living in the Great White North of Canada where the price of gas is higher. It's a great challenge, Gavyn, and certainly achievable. Many years ago (around 1993), we built a 302ci small-block Chevy with a goal of 550 hp and 25 mpg using a Vortech centrifugal supercharger and EFI fuel control. We built the engine using AFR 195cc heads, a short-duration Crane mechanical roller camshaft, 9.0:1 compression, and an ACCEL EFI electronics package. On the dyno, the engine made 549 hp and later achieved 23 mpg highway mileage.

Today, we'd build a different engine. To take advantage of current technology, I'd choose a 5.3L (326ci) GM Gen III engine with full EFI control, using the factory GM computer because it has such tremendous control, and tune it with a program such as HP Tuner. The 5.3L is used as a truck engine but still retains all the advantages of the Gen III architecture including a 15-degree valve angle for better cylinder-head airflow. We'd run a set of ported heads with slightly larger valve sizes and bump the compression up with a set of forged pistons to run around 10.0:1 static compression and take full advantage of running cheap 87-octane fuel. This may seem like a lot of compression, but keep in mind that the Gen III engines have an outstanding combustion chamber and also benefit from state-of-the-art detonation sensor technology that will pull timing back if the engine begins to rattle. We'd also run pistons with very thin 1.5mm rings to not only improve ring seal, but also to reduce friction. We'd want to try several different camshaft profiles as well to see which one would run the best with 87-octane fuel.

A difficulty with this type of engine is that maximizing cylinder pressure for good mileage and power will run up against the octane limit of the less expensive, low-octane fuel. One way to minimize that effect would be to use water injection at wide-open throttle (WOT), which should reduce the engine's sensitivity to detonation. We'd also run relatively small-diameter headers in an effort to build torque since we're building a rather small-displacement engine. If mileage was really the key, you could also jump down to a 4.8L (293ci) Gen III engine, but this extracts a greater price in terms of torque and horsepower. I think that a normally aspirated 5.3L small-block like this could easily knock down 25 to 27 mpg. Getting to 30 mpg would be difficult and would probably require running the car in a smaller body style, preferably with a slippery shape like a third-generation Camaro, to squeak up close to the mileage goal. Of course, this would entail using a manual transmission and certainly an overdrive. We just had a meeting with the folks at Keisler, and they are introducing a retrofit kit using the '94-'01 Mustang T45 five-speed trans for most popular Chevys and the early Mustangs. This is an affordable trans that is a good fit for this application since we are not making 500 hp. As far as power is concerned, I think that your goal is conservative. I believe that this motor could actually make around 1 hp/ci at around 325 hp or more. Torque would not be as substantial only because of the limited displacement, but it would still run strong, especially with a manual five-speed in a relatively light car like an early Chevy II.

This would be a fun project, Gavyn. If we see enough interest from the rest of the Car Craft clan, we could be persuaded to tweak an engine like this, and we'd tell you everything. A similar idea could be cooked up for the Ford guys using a 5.0L 302 engine or perhaps a two-valve Mod motor. Regardless of the name stamped on the valve cover, the idea is to build an engine that is still performance-oriented but with a goal tipped in favor of optimal efficiency rather than just max power.