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Is my (1969-1972) a true SS?

 

Regardless of year, there are no known numbers of any SS option (RPO Z25 or RPO Z15) by body style. Any time you see an SS-optioned Chevelle with a claim of "one of xxx" that claimed number is made-up. While the Chevrolet division of General Motors may have had, at one time, the number of any possible body style and the number of SS options for that body style but no numbers were ever officially published. Why not? Whey would Chevrolet care? With the exception of the 1969 model year, the SS options were only available with the Malibu sport coupe, convertible, and El Camino.

 

1969

Now, one can calculate an even distribution of an SS option based on the percentage of the body style vs. total sales and then multiply the percentage with the total number of SS sales. For example, the 1969 model year. The first matrix shows the V8  series/model, total of that series/model reported by Chevrolet sold, and the percentage of that series/model against the total. The percentages are, in fact, a bit off the Malibu sport coupe (13637) since 323 of those were converted to 427cid COPO cars so they can't be part of the calculations for SS 396 optioned Chevelles. From Chevrolet is the number of SS 396 options sold overall is 86,307.

 

Taking into account the 'Possibilities' in the matrix is a calculated distribution of the option vs. the series/model, one can go a step further and calculate the number of different engine possibilities for each series/model. Unfortunately, the number of 396/302 engines reported by the Tonawanda engine plant (86,220) for 1969 doesn't match the number of SS 396 options reported in 1969 by Chevrolet (86,307). And, it gets even worse for 1969 with the 323 COPO Malibu sport coupes. The build sheet on a 1969 COPO Chevelle shows the L78 engine. A question then arises, are the L78 engines on COPO build sheets included in the 400 L78 engines reported by Tonawanda? If that were the case the only a total of 87 1969 Chevelles went out of the factory plants with the L78 engine and 400 of those (87) were optioned with the L89 aluminum heads. So, just where those 323 L78 engines went is a mystery. Strangely that same 87 number pops up when comparing the number of 396/402 engines reported (86,220) vs. the number of SS options sold (86,307).

 

 

1970

The 1970 model year saw two SS options, RPO Z25 for the 396/402 and RPO Z15 for the 454. The Z25 option could be ordered with one of two engines, the L34 350hp engine or the optional L78 375hp engine. The number of 350hp engines is easily found by subtracting the number of L78 optional engines (2,144) from the total Z25 options (53,599). Likewise the number of LS5 engines can be determined by subtracting the known number of LS6 engine options (4,475) from the total Z15 options (8,773). Fewer calculations are required for 1970 since either SS option was limited to three V8 series/models.

 

One must first calculate the percentage of each series/model against the total 1970 Chevelles built and possible SS optioned Chevelles (65,372). From that we can see that the Malibu sport coupe (13637) made up 85.82% of all 1970 Chevelles; the 13667 Malibu convertible is only 2.12% and the El Camino at 12.07%.

 

Then take the percentages above vs. the number of Z15 and Z25 options. And, finally, break each calculated possibility vs. the four engines themselves. The question now becomes are these numbers correct? It depends on which numbers one is referring to. The known total of 1970 Chevelles in those three series/models is known and the number of each engine is known. Everything else (engine vs. series/model) is an evenly distributed calculation and not a true number of engines vs. series/model.

 

 

Some have tried to take the options possibilities even further with ZL2 hoods, M40 transmissions, M20/M21/M22 transmissions, etc. Here's where a BIG problem arises. The ZL2 cowl induction hood could be ordered on any SS396 and any SS454; that's three series/models and four different engines. Now you're calculation possibilities from a calculated possibility number and results get even more muddled. The same is true for transmissions, the M20/M21 could be ordered with not only the SS396 but with any 350cid or LS3 engine. The M40 TH400 transmission could be ordered with any LS3 engine. So, there's no way to know how many M40 transmissions were ordered with one of the two SS options, or how many M20/M21 transmissions were ordered with the SS396 option.

 

1971/1972

The 1971 and 1972 model years is, for all practical reasons, impossible to calculate the number of specific engines for a given series/model. Both 350cid engines and the LS3 402cid engine could be ordered with or without the SS option. Only the LS5 454cid engine REQUIRED the SS option in both years. As such, only the LS5 454cid engine option can even be considered.

 

 

 

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