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Regarding the Article...
All explicit information herein is believed correct to the best of my knowledge, and has been extensively researched with the available literature (the primary references are listed in the footnotes) and and/or verified by hardware on actual cars. There remain poorly understood documentation differences between some of the details of the two model years, 1967 and 1968. Where part numbers are not explicitly referenced, the referenced feature has been verified on the 68 model, but not necessarily on the 67 model. The author would appreciate being contacted about any corrections, deletions, or additions to this information.
About the Author...
Rich Fields, a Senior Staff Engineer with Lockheed Martin, has a number of writings on technical issues associated with structures made from composite materials, especially in aerospace applications. While a long-time admirer of the SBC engine, he has only relatively recently turned his personal time toward researching and documenting the technical aspects of first-generation Camaros. This is his first article on this subject. He owns and is presently restoring a 1968 L30/M20 RS Camaro.
Foot Notes...
(Please note: Foot notes are bookmarked- click on numerals to return to corresponding text)
1.In addition to the 275HP L30, the 327 engine was available (in other Chevrolet models) in variants of 300 to 350HP, more than sufficient to power the small-block version of the Camaro SS. The 350ci engine was developed, according to Camaro engineers of the time, largely as a marketing vehicle to the cubic-inch oriented public, to combat the Ford Mustang 351 engine. Likewise, the 396, offered as a mid-67 Camaro addition, was intended to balance the Ford 390 engine available in the Mustang and stifle criticism of a lack of muscle-car raw power.
2. The L30 engine was eliminated for 1969 and replaced with a slightly lower-performance, detuned 350ci RPO LM1 engine that developed 255HP on regular octane gasoline. The LM1 was sufficiently powerful to be considered "high-performance" when teamed with a manual transmission, but was a noticeable drop in performance below the now 300HP L48. However, the basic concept for the LM1/M20 in 1969 was the same as the L30/M20 in 1967-68; a lower-priced, low-profile, performance Camaro with a significant package of high-performance components. To Chevrolet’s credit, the LM1 was given the Muncie 4-speed rather than the Saginaw 4-speed with which the L30 was saddled.
3. Though Chevrolet, upon request, provides Camaro specification documentation that includes this data.
4. Gib Hufstader, May 1997. Some exceptions remain, but the demise of central Chevrolet Central Engineering into the melting pot of GM Engineering, and the retirement and passing of key Camaro engineers now makes this data all that more difficult to trace and find.
5. Camaro Enthusiast, Spring 97.
6. This assumes that one considers the 400ci SBC engine of the early to mid 70’s, with its siamesed bores and externally balanced assembly, to be more of a distant cousin than a direct descendent. Of course there were other subsequent SBC engines with direct lineage to the 265, including the short-lived and specialized 302, the poorly appreciated 307 (developed for low-performance emission-control), and later on, the generally well-respected 305; but none of these were engine expansions in the same sense as the 350.
7. The new 350 crankshaft also introduced a broader change that affected the other small-block V8 engines; the diameter of the main bearing journal was increased in size from 2.30 inch to 2.45 inch. Except for the 1967 350 (which inaugurated the "large-journal" crank), engines from 1967 and earlier used the "small-journal" crank while all engines from 1968 and later used the 2.45-inch diameter "large-journal" crank. Since 1968 was the last year for the high-performance 327, it was also the only year that a forged-steel 327 large-journal crank was produced. The low-end, 2-BBL carburetor, 327 used a money-saving but lower-strength cast-iron crank; by mid-year 1969 the 327 was totally phased out in favor of the lowly 307 engine.
8. In 1969, the RPO code for the Camaro SS package was changed to Z27 and the L48 code became strictly an engine sub-option for the Z27 code.
9. The "high-performance" designation was, and still is, an arbitrary classification. The difference was often one of interpretation, or a matter of expectation. In the case of the L30, the four-speed model was considered by the public to be a "hotter" car. The dividing line moved somewhat in 1969; the successor to the L30, the 350ci LM1 with 20 less HP, was considered higher performance when mounted to any manual transmission! While these models were not all-out slaves to the horsepower gods, and so probably not worthy of being called true "muscle" cars, they certainly earn the "high-performance" appellation.
10. The 10-bolt rear end has had, at various times during its history, a number of different ring gear diameters. During the first-generation Camaro years, the 10-bolt used a 8.125 inch gear. With the 1970 model Camaros the 12-bolt rear end was phased out and the 10-bolt redesigned to use a more robust, more universally suitable, 8.5 inch diameter ring gear. During the low-power years of the mid 70s to early 80s, the 10-bolt ring gear diameter was reduced to as small as 7.5 inches.
11. The Muncie transmission was the only SS performance component not available to the L30/M20 as a factory option. This was the only significant shortfall of the L30/M20. While the Saginaw was sufficiently functional, the Muncie was superior and therefore more desirable. The Muncie was not only lighter due to the aluminum case, it was simply a better design, and the gears were constructed from higher quality steels. This didn’t necessarily make a Muncie car any faster, but it was certainly less prone to problems in a demanding environment. The Saginaw was disdained more for its low-end origin (the Saginaw 4-speed was developed for the Corvair) than for any inability, real or imagined, to perform. The cast-iron case was a visible sign that the Saginaw was visibly "low-tech", but it saved Chevrolet some $75 per unit over the Muncie. Yet Chevrolet charged buyers the same price for an "M20" option, regardless of which unit it actually installed.
12. Deduced from CAC/AMA weight tables for various 1968 Camaros with various option groups.
13. Antonick, White Book of Camaros, 1993.
14. Please contact the author if you have, or believe you have, an authentic L30/M20. He would like to develop a registry of this option combination.
15. Not offered in domestic Camaros; production of 283 engines ended with the 1967 model year, replaced with the low-power 327 in 1968 and early 1969, which was itself replaced in mid-1969 with the 307.
16. A valid historical argument could be made that the L30 engine was more the 327 historical norm, with the 210HP version a departure from the L30.
17. The standard dual exhausts on the L48 were not a factor in the gross horsepower numbers, since a common dynamometer exhaust system was used in the gross horsepower tests of that day.
18. The 1967 L30 engine used the "small-journal" crank with a 2.30 inch diameter main journal and a 2.00 inch diameter rod journal. In 1968 the switch was completed to the "large-journal" crank with a 2.45-inch diameter main journal and a 2.10-inch diameter rod journal, the same dimensions used on the L48 in both years.
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