Wednesday, July 13, 2016

Rebuilding and Upgrading the Corvette L-48 Engine | Part 1

By the early 1970s, "horsepower" had become a four-letter-word in America thanks to the combined efforts of insurance companies, environmentalists, and the federal government, not to mention an oil crisis that quadrupled fuel prices.

So when the then-new 1976 Stingray models rolled off the line, they featured anemic 180 hp base motors with 8.5:1 compression ratios. The "high-performance" L-82 option barely managed to bump that number up to 210 ponies.


The irony is that fuel efficiency was nothing to brag about either, with the L-48 being capable of only 13.6 highway miles-per-gallon. For comparison purposes, the new 2016 Corvette has a 460 hp 6.2L V8 with an estimated 29 MPG. The 2016 Camaro churns out 335 horses with a 27 MPG highway fuel efficiency out of the base 3.6L V6 engine!

So when the time came to make a decision to have the original 5.7L rebuilt, bumping up the horsepower was a no-brainer.


I considered a crate motor, which would've saved me a few bucks as well as provided a warranty, but almost everyone I talked to, suggested keeping the original engine with the car. Numbers-matching has  a certain allure that trumps a crate motor every time.

Besides, getting an L-48 block to generate 300 horses does not take much money or effort. Going beyond that number translates into a car without good street manners, which is not something I am interested in.

My goal is having the original engine built to a level that justifies it powering a Corvette, while being reliable, streetable, leak-free (more than a few C3 owners will understand), and able to return a decent miles-per-gallon average.

The plan is to have the motor rebuilt and balanced, the cylinder heads will be ported, the valves will receive a 3-angle job, all new seals and gaskets, and new pistons will be installed in order to bring the compression ratio up. This will require the use of premium fuel, but I am fine with that compromise.

So today's the day when I will drop off my Vette at a local shop that will remove the motor and send it out to be rebuilt, a process that should take about a month or so.

Of course there's always the chance to uncover other systems that may need attention while the engine is being rebuilt, so things like the clutch, for example, will be checked thoroughly in case it needs to be repaired or replaced.

Stay tuned for Part 2 of this series.

Thanks for reading.