SuperFast80

And why did it not offer it in the Chevelle in 1971? :confused: :confused: :confused:

This is strange to me because they obviously had it certified in both years.

Is the answer that the Corvette was to get the LS-7 and therefore Chevelle didn't get the best engine in 1970, only the best to make it through final certification? So then in 1971, when the LS-6 was the top engine, they restored the natural order and offered it only in the Corvette?

67HEAVEN? cruz? Chuck Harmon? anyone?

1Bad69

http://www.vette.ch/en/techinfo/ls6.htm

67HEAVEN

I think it all boils down to too late! The planned for (and then cancelled) LS-7 in the Corvette got in the way of the LS-6 in the Corvette. Corvette was to have the LS-5 and the LS-7, Camaro to get the LS-5 and LS-6 and Chevelle to get the LS-5 and LS-6 and LS-7.

When the LS-7 Corvette was cancelled, it was then too late to design and get approved a low-rise intake manifold for the LS-6 in the Corvette for 1970. (Note: the LS-6 was to have cast iron CLOSED-chamber heads, the LS-7 was to get aluminum OPEN-chamber heads). Apparently they couldn't, or wouldn't, use the LS-5 intake.

Then, in 1971, when the Corvette finally got the LS-6, it also got the still-born LS-7's aluminum OPEN-chamber heads.

Sidebar: This also led to RPO ZR-2 in 1971 which included the LS-6 454, M-22 rock crusher, F-41 HD Suspension, J-50/J-56 Heavy Duty Power Brakes, the old L-88 Harrison aluminum rad without shroud, no radio, no air conditioning. This ZR-2 option cost $1,747 and only 12 were sold in 1971.

67HEAVEN

By the way, even though it was no LS-7, the LS-6 was no slouch. Car Craft Magazine managed a 12.64 / 114.21 quarter-mile using headers, 4.56:1 and slicks

Solidlifters

Interesting link, but I don't think it answers the question and I don't know the answer either. Of course the rumor's always been that the engineers wanted the LS7 in 70 and the front office said no, but that really doesn't explain why they didn't go ahead with the LS6's. Why they dropped it in the Chevelle/El Camino in 71 while finally putting it in the Corvette has always been a question mark also. I also don't understand why they dropped ALL the SHP big blocks from the Novas & Camaros after the 70 375's and why they didn't go ahead with the LS6's in these two platforms as well. Somebody out there oughta know the real reasons instead of all the guesses and opinions that we always get when this subject pops up.

Double Aught

What I recall reading about the aborted LS-7 is GM couldn't certify the motor before the 70 production ramped up. They striked that year, if memory serves. Also, the effing insurance companies started to come down hard on super high performance cars, with exorbitant premiums. So GM killed it for the Vette. I bet Superfast has an article buried somewhere that tells the whole story. Typical GM b.s. is what you are likely to discover. :yesnod:


[Modified by sd pacecar, 6:51 PM 9/2/2002]

joe58

In my opinion, the Corvette engines got the ax as part of John DeLorean's "deproliferation" program. He was promoted to Chevy general manager from Pontiac in 1969 as a fast track new style management wonder boy. Chevy had high sales but poor profit margins. One of DeLorean's ideas was to cut down the car models, parts, and optional equipment. He had cost benefit studies done that showed a high percentage of the options went into a very small percentage of the cars built. Any optional equipment which was ordered on 5 percent or less of production was an immediate candidate for elimination. The guy who made the GTO axed the hot 70 Corvette engines as part of his cost reduction plan. IMO

Turbo-Jet

I am pretty sure the LS6 was planned for 72, because it is included in the 1972 AIM, but has 'CANCELED' stamped on it's pages. I wonder the exact reason it was axed?

Rowdy Rat

A combination of events led to the cancellation of high performance engines in the early 1970s.

Deproliferation, as Joe mentioned, was one of these... There were a lot of options available that generated very low sales volume and tended to be less (or not) profitable. One of the ways to reduce production headaches and improve profitability was to eliminate these low volume options and this is exactly what GM did. In addition to the LS-7, it is also responsible in part for the demise of the other planned 1970 Corvette engines; LT-2, LJ-1, and LJ-2.

Insurance for high performance cars was becoming a major problem as well. Yearly insurance costs approaching 1/3 the price of the car were not unheard of.

Government emissions regulations, especially those relating to phasing out leaded fuel also played a major part. It all went back to cost in the end; there just wasn't any logical reason to go through all the development work and expense required to meet the government standards for a low volume engine in a car that would be hard to sell (and would probably be a warranty headache if it did).

Those are my thoughts anyway...

Regards,

SuperFast80

Stan, can you tell me more about the LT-2, LJ-1 and LJ-2?

Rowdy Rat

The intake manifold wasn't an issue at all as a low rise, rectangular port, aluminum intake manifold (for use with a Holley carburetor) had already been designed specifically for use in the Corvette for the 1970 model year. This intake was used on all special high performance big blocks in 1970 (including those built during the 1969 calendar year)... The rest of Chevrolet's high performance cars got stuck with this manifold even though there was sufficient room under the hoods of Chevelles, Camaros, and Novas for the old high rise intake. In addition, the 1970 AIM calls for the standard big block hood to be used with the LS-7 (not the ZL-2 cowl induction hood from the L-88/ZL-1); the only rectangular port, Holley manifold that would fit under this hood would be the "no rise" manifold previously described. Obviously, the engineers were well aware that they would be using a low profile manifold for the LS-7 option.

If GM records are to be believed, the production LS-7 in its final form was to be nothing more than a warmed over LS-6. The cylinder head specifications that GM submitted to the AMA for the LS-7 clearly indicate a closed chamber, aluminum cylinder head. The advertised compression ratio of 11.25 to 1 is also identical to the 1970 LS-6 engine. Considering that the 1970 LS-6 did use closed chamber, cast iron heads and that nearly all of the other published specifications for the two engines were identical, it seems pretty obvious that GM simply swapped the aluminum, closed chamber cylinder heads for the cast iron versions used on the Chevelle/El Camino.

The only strange part of the whole LS-7 package is the camshaft. Lift is specified as .520/.550 which is a bit different on the exhaust side than the "143" high performance street cam. Duration was identical to the second design L-88/ZL-1 cam and to be honest, I don't know what to make of this... I guess it could be an error, but I doubt it. I'd really like to hear the real story behind this issue.

The 1971 LS-6 Corvette did use the open chamber aluminum heads from the second design L-88/ZL-1. This was more a matter of expediency as it was a quick way to drop compression without much engineering effort. It also gave the customer something visible to help justify the $1,200+ option price.

Regards,

Rowdy Rat

LT-2 was to be a 454 cid version of the 1969 ZL-1 engine... Aluminum block, aluminum open chamber heads, etc. There really isn't a lot of information available that I am aware of. It was apparently dropped early as a viable RPO for 1970 as it never made the engineering drawings.

LJ-1 and LJ-2 were 454 cid versions of the 1969 L-71 and L-68 engines. Basically, they were tripower 454s. These engines are referenced in the 1970 AIM and were dropped as RPOs well before the 1970 calendar year.

If not for the strike which resulted in the extended 1969 production run, Chevrolet might have actually offered these engines in the 1970 Corvette.

Regards,

SuperFast80

FWIW, here are 1970 engine specs (including LS-7) as they appeared in March 1970 Chevrolet Service News: