LS7Vette

Can you post the pictures of the console data plates?

thanks,
Ray

parkerracing

The strike that year may have had as much influence as anything else in GM's decision to kill those options.

'70ls-7

The red 70 convertible is from Vette magazine Jan. '91. It's my car! I bought it from my Dad 12 years ago. It is closer to the LT-2 than the LS-7 having the aluminum Yenko Can-Am block vs. the iron block the LS-7 would have came with. Originally started life as a LS-5 car in Bridgehampton blue. The car is also featured in Corvette: The complete Illustrated History by Jim Campisano.

69 Chevy

Pg 128 of Vette Vues Fact Book 1968-1972 Stingray:

mmoore289

As the son of a dealer, I had as a demo a 1972 LS-7 Corvette. 454 460 hp which I drove for many months till it had some miles on it and then it was time to order something else to drive. We normally switched cars around 5000 miles so I always got to drive many cars throught the year. All were the most high performance and with the most options. It was nice being a dealers son.

69 Chevy

ZOWIE!!! That must have been one rare car. Not a single reference book in my library lists any big block engine option other than the 270hp, 8.5:1 comp ratio, hydraulic cammed, Q-jet LS 5 for the '72 model year. You know, where low compression for unleaded gas and net horsepower figures were used. I wonder what St. Louis big shot had enough clout to have that car built?

joewill

yes there are many references in the 70' AIM regarding the LS7 and its options.

kelwald

March 70 issue of Sports Car Graphic has the article with pictures. One in color. Looks like Ontario Orange which wasn't a 70 color or Bronze. Article also in Motor Trend. I have a 71 that was an LS-5 but now has the LS-7 Crate along with M-22, dual-disc clutch, Al. heads, 410 rear which I believe all would have been options. The test car had the low-rise intake and stock BB Hood. The test car allegedly was crushed per GM policy but some workers claim the motor was pulled out and stolen. Yet another article claimed 5 LS-7 motors where shipped to St. Louis plant but never used.

c6silver

[QUOTE=Rowdy Rat;1573598976]Should make for a nice tribute car!



Not really.

The LS-7 engine intended for production (NOT the service engine that showed up in 1972-73) would have been very similar to the Chevelle LS-6 engine available in 1970 with the exception of closed chamber aluminum heads in place of the cast iron Chevelle units and a transistorized ignition system. It did not use the cowl induction hood from the L-88/ZL-1 cars and could be ordered with a radio. Air conditioning was not available.




As mentioned above, it would have the normal big block hood, but the induction system would have been a single four barrel Holley carburetor on a low rise aluminum manifold. It is interesting to note that this manifold was used on all the other solid lifter big blocks in 1970, but wasn't really needed as Camaros, Chevelles, and Novas had plenty of clearance... The only car that needed it was the Corvette and the engine that would have used it (the LS-7) wasn't produced for sale.



That's it.

The LS-7 was going to be a special high performance street engine... Contrary to the legend that has grown up around it.



It's true that there were two ratings that showed up. GM finally released a rating of 460 horsepower and that's what is printed in their literature so that is what I am inclined to believe. I do there was considerable time and effort made to certify the engine in time for the 1970 model year and it is possible that changes were made that reduced the rating over time.



Warren noted the two period magazines that feature the car. None have high quality photos that we are used to today, but they are passable and the information in the articles are pretty accurate.

Regards,

Stan Falenski[/QUOT
Incorrect. The 70 LS-7 would have had OPEN chamber heads like the 69 L-88 before it, and I HAVE to believe the same high rise intake as the L-88 with the L-88 hood. The 70 Chevelle LS-6 had the high rise intake, and Chevy wouldn't have let it be top dawg over the almighty Corvette, so the Vette would have had the BEST parts available to do the job. This was 1970, the HP war was raging and to put on a low rise intake would have killed power potential, the LS-7 was going to be the most powerful engine Chevy ever made. I would LOVE to see F.A.S.T or Supercar Racers let the LS-7 compete (Chevy did build AT LEAST 1),BUT because it wasn't sold to the public the '69 L-88 is top dog for Chevy in those classes.

Zoomin

It's intriguing to me that Chevelle got the LS6 in 1970 but the Vette did not.

early shark

You're going to also need the heavy duty MA6 option to go along with your heavy duty M22 transmission.

Rowdy Rat

For the intended production version of the LS-7, closed chamber heads are indeed what would have been used. The part number and engineering drawings for the 1970 LS-6 and LS-7 pistons are the same. The compression ratios for the 1970 LS-6 and LS-7 are the same at 11.25 to 1. The 1970 LS-6 used a closed chamber head. I guarantee you the easy way to get an aluminum head on an engine with that criteria is to use the 842 closed chamber head. And for what it's worth, the early 1970 Chevelles had the L-78 option available with the L-89 aluminum head option. Guess which head Chevy used? Yes... The 842 closed chamber head.

As far as the intake, it was definitely the low rise 569 casting similar to the 1971 LS-6 Corvette. The photos of the LS-7 that we do have show a standard big block hood... No way to get the high rise 163 casting intake under a regular big block hood. Also for what it's worth, that low rise intake created for use on the LS-7 was forced on the rest of Chevy's lineup including L-78 Novas, Camaros, and Chevelles as well as most LS-6 Chevelles (I've heard that some of the very early LS-6s came through with the high rise intake, but afraid that I don't know those cars well enough to comment on this) even though they could use the 163 casting with no clearance issues.

The 1970 PRODUCTION LS-7 engine for the Corvette would have been pretty similar to the 1970 Chevelle LS-6 with the exception of the aluminum heads, transistor ignition, and open element air filter (and Corvette specific oil pan and exhaust manifolds). It would have been the most powerful STREET engine Chevy would have built... Which isn't such a bad thing.

Regards,

Stan

kelwald

NHRA certified the LS7 for SuperStock B/BA. Seen the only one at the Gatornationals in 1975. Have videos of it along with his partner Bernie Agaman who was running SS/CA with a 71 LS6 and ended up winning the SS championship for the year. The person running the 7 was Claude Urevig and competed against the Hemis but won the SS/BA class with sub teen 10 second runs. He sold the car and the new owners switched it to a 71 with the LS6 powerplant

c6silver

1970 Chevelles with the LS-6 got a high rise intake, and 1969 L-88s got open chamber heads, which are known to flow better, why would Chevy handicap their newest high performance engine with anything less than the best ? NO WAY... the other 2 versions mentioned LT-2 and LJ-2 tri-powers would have had a normal big block hood, the LS-7 would not be using a pancake intake and inferior closed chamber heads...this engine was the L-88 replacement (before it was killed, anyway). The added stroke of the 454 and the resulting torque (and HP) increases would have made the LS-7 more flexible and taken some of the "edge" off the L-88s high strung nature, which would have allowed more "normal" street gearing (4.10 or so). It would have also made compression easier to achieve than a 427, there was no need for closed chamber heads.

Rowdy Rat

Most didn't. The vast majority (99%+) used the 569 low rise intake. As I mentioned before, there may have been some very early LS-6 Chevelles that used the 163 intake, but I don't know or follow Chevelles enough to know if a consensus was ever reached on that topic. I can tell you that most of them (along with every L-78 engine installed in a Chevy that year) received the low rise 569 manifold and the only reason that Chevy did that was because of the LS-7 Corvette.

Some 1969 L-88s received open chamber heads. Those built before the strike typically used the 842 closed chamber heads and were coded "IT" like the 1967-1968 engines. Later L-88s coded "LO" or "LV" (along with ZL-1) used the 074 open chamber heads. They also used a different camshaft, a different carburetor, and of course a piston designed to work with the open chamber head.

Chevy still used the 842 closed chamber head on street performance engines under the L-89 option (the last cars to receive them were very early 1970 L-78 Chevelles)... So they were still being used at that point.

The LS-7 intended for 1970 production, regardless of what has been printed by current day "Corvette" magazines or passed down as a result of urban legend, was a high performance STREET engine. It had 11.25 to 1 compression (AMA specs, GM tune up info, owner's manual), used a standard big block hood (period photos of prototype, AIM), had an open element air cleaner (period photos of prototype, AIM), used a hybrid street mechanical cam (AMA specs, GM tune up info), vacuum secondary carburetor (AIM), TI distributor WITH provision for vacuum advance (AIM), was available with a radio (period photos of prototype, AIM)... The list goes on. It had very little in common with the L-88 of 1969.

If nothing else, look at the technical specifications for the LS-6/LS-7 pistons for 1970 (you'll find they are the same). Look at the compression ratio for both engines (they are the same). Look at what head the Chevelle LS-6 was using in 1970... 291 closed chamber, cast iron. We know that the LS-7 would have used an aluminum head so how do we keep the same compression, using the same piston as an LS-6? The answer is pretty simple... Use the closed chamber 842 head.

LT-2 was a 454 version of the ZL-1... That's pretty clear. It WAS the pseudo-race engine and would have used the cowl induction hood and all of the heavy duty brake and suspension parts. LJ-1 and LJ-2 were 454 versions of the L-71 and L-68. They were the front runners for the Corvette street performance engine until tripower got the axe. Both were killed off relatively early... LT-2 isn't even mentioned in the AIM while there are brief references to LJ-1 and LJ-2. Any potential "454 L-88" type engine would have been dead in the water as quickly as LT-2. Low volume and low margin were not in line with GM marketing plans in 1970.

By the way, when tripower was eliminated as too complex and costly, Corvette engineers needed a single four barrel aluminum intake set up to accept a Holley carburetor that would fit under a standard big block hood. They came up with the 569...

Look at it this way... 1970 was the year of deproliferation for GM. John DeLorean had laid down the law that low volume options were "out" for all GM divisions... LT-2 was cancelled immediately. LJ1 and LJ2 were out as well. Corvette was left without a high performance engine for 1970. The engineers circled the wagons and took their best shot at a performance engine that could be sold to management... Basically an (already in production) LS-6 with aluminum heads. Good plan, but apparently it still wasn't good enough to move forward as an available RPO.

Regards,

Stan

c6silver

Goddamn DeLorean. Pontiac guy through and through, was sour grapes over Chevy kicking his *** for so many years at the drag strip that he screwed them under the guise of deproliferation... Although, to be fair, Pontiac lost the legendary Ram Air V engine for 1970 as well...

So tell me this then, besides compression and cam shaft specs, what are the differences between the 1970 LS-7 and the 1971 LS-6 ? What are the LS-7 cam specs ?

Rowdy Rat

DeLorean was actually using good business sense, but it was taken to the extreme (although he apparently DID get some enjoyment sticking it to Chevy from what I've read). Car manufacturers' today use similar principles in marketing options and is one of the reasons why you can't truly build a car entirely to your own taste today. Options are limited and you are forced into ordering option "packages" to help streamline the production process. Efficient, but definitely not as interesting as ordering a new car used to be.

Years ago, I rode along with a friend delivering a Yenko Camaro to its owner after it had been restored. The gentleman who owned the car also had a fantastic Pontiac collection. He built a 1969 Ram Air V GTO from parts... Had an M-22 transmission and 4.56 rear. I wish I had taken photos of it because it was one of the coolest cars I've ever been around!

The heads were the big thing. The 1971 LS-6 actually DID get the 074 open chamber head. This was done mainly to drop compression ratio, but it also took some weight off of the front end. In addition, it gave the buyer something "visible" (i.e. alloy heads) for the $1,200 they were shelling out for the privilege owning one.

The camshaft originally slated for the LS-7 was .520/.550 lift part. I originally thought that it was a typo... The 143 mechanical cam that was typically used in high performance street applications (and was used in both the 1970 and 1971 LS-6) is listed as .520/.520 so it made sense that someone might have made a mistake. Turns out that one of the reasons for the cancellation of the option was the difficulty in getting it certified (the 1971 LS-6 ran into similar issues). It actually makes more sense if the engineers were playing around a bit with cam profile on the exhaust side... Just to try and clean things up a bit.

For comparison, the early L-88s used a .540/.560 lift (# 3925535) cam and the later L-88s and ZL-1s used a .560/.600 lift (# 3959180) cam.

People don't realize how lucky Chevy was to get the 1971 LS-6 into production. Certifying this engine was a continuation of the work begun on the LS-7... It took them that long to get it right. If they had not, the last high performance big block would have been built in 1969!

Regards,

Stan

FlyLS6

LS 7 spec according to Fisher:

http://books.google.com/books?id=1kX...page&q&f=false

c6silver

High Performance Pontiac magazine reported on a Ram Air V GTO being built by Purely PMD in Albuquerque NM back in the early 90s, and that they had tracked down the ONLY pair of A body RAM AIR V exhaust manifolds in existence, the ONLY hood tach with the correct redline for the Ram Air V, and a bunch of other parts...was this the car you saw ? I believe it was that red that looks orange. Pete McCarthy wrote in one of his books about an internal Hydramatic (GM) document that showed a workup of a torque converter with a much higher stall speed than anything else GM had made prior to that point and transmission calibration information (6000+ upshift for one thing I think) with a line drawn through it, and he was heartbroken because he knew that line meant the project was cancelled. I have a friend that has a HUGE stash of Pontiac parts, he has some Ram Air V stuff...

I do understand the reasons behind deproliferation, and how it affected option packages, and the economic reasons behind it, but it sucks that the bean counters win out, especially with a niche vehicle like the Vette, halo cars with big power attract buyers to showrooms, and the LS-7 etc... would have helped GM in the long run...to bad they didn't understand about quench clearance, heart shaped chambers, crevice volume, and unleaded gas...those mighty engines might have stuck around a lot longer, and run cleaner to boot.

According to the link posted above to the Fisher book, the pistons are NOT the same, the LS-7 would have 1/16 rings and floating pins, the LS-6 had standard 5/64 rings and press fit pistons. FWIW

68/70Vette

My 1970 AIM shows the 3X2 barrel carburetors as an option (discontinued).