Frequently Asked Questions
Q: How many L78 convertibles were built?
A: There is no known breakdown of L78 optioned Chevelles by body style or how many came with optional gear ratios, specific transmissions, radios, etc. and will probably never be known unless I can register and document all L78 cars sold, which isn't in the realm of possibility for obvious reasons.
See How Many L78's Based On Body Style Were Sold? for more insight on L78 numbers vs. body styles.
Q: Didn't all L78 cars have gauges and a tachometer?
A: No. The Instrument Panel Gauges, or Special Instrumentation, sold under RPO U14 was always an option regardless of year.
Q: Is my L78 real?
A: This can be tricky at best. To some, 'real' means the car has the correct and original engine it was born with and can be matched to some form of documentation. To some, it means if the documentation says it was born with the L78 option, it doesn't (relatively) matter that the engine has been replaced for one reason or another; whether by a dealer under warranty or an over-avid enthusiast 'back-in-the-day' due to out of warranty breakage. Consider if the car has a warranty engine with CE code or a base 396/350 motor dressed to appear as a L78 engine, but has documentation that is original to the car as noted by the VIN sequence and other information of the sheet matching the trim tag.
As far as the L78 Registry is concerned, correct and valid documentation is the primary objective in the registry, not current engine.
Q: Wasn't there an L89 engine as well?
A: No. There was an L89 aluminum head option but it was only available on the L78 engine.
Q: When did the L78 become available?
A: According to an GM internal engineering memo dated in December of 1965 the L78 was axed prior to the beginning of production of the 1966 model year, but was "reinstated" in late August of 1965. There was no advertisement of the availability of the L78 to dealers until February 1966, and no public advertising until later than that. And the option was never added to the Chevelle/El Camino order form at any time during the model year. It had to be penned in in a blank line beneath the pre-printed list of available engine options.
The production of the L78 officially ceased being available, or more accurately "...in the process of being cancelled..." in a GM letter dated October of 1969 that coincided with the introduction of the LS6 engine option for the 1970 model year. The last known (at this time) dates for an L78 optioned Chevelle from Atlanta has a scheduled date of November 12, for Baltimore it's November 25, for Van Nuys it's October 11. I have no build sheet data for Arlington, Flint, or Kansas City to verify those three plants. For more information on the LS6 engine option, see the LS6 Registry at http://ls6registry.com.