1970 LS-7 engine

[Stan F.]

Re: 1970 LS-7 engine

Pat,

Some really interesting items in that photo…

First is the carburetor/intake manifold arrangement. Obviously a low rise intake with a vacuum secondary carburetor. The fuel line arrangement is the same as a 1971 LS-6… Even has the stamped fuel line support. There is also an operational choke which was never used on an L-88. I found the TCS solenoid location to be interesting as well. I am curious if the solenoid for the LS-6 Chevelles was in the same place. Finally, it looks like this car might be NA-9 equipped… The heat shield for the carburetor is clearly visible.

The radiator is the copper/brass variety, not aluminum (as would be found on a manual transmission L-88). Overflow tank is also copper/brass which was typically reserved for C-60 equipped cars. There is also a fan shroud of the type consistent with a copper/brass radiator.

Fuel and vent line present. Unusual for Holley equipped cars which typically used only a fuel line. The only other Holley equipped Corvette I am aware of that used two lines was the 1971 LS-6.

The alternator bracket appears to be the type used with power steering equipped, big block cars. L-88s were never available with power steering.

The A.I.R. Pump is interesting… The pump with the pressure relief valve was used through most of 1968 across the board. For the 1969 model year, this feature was eliminated except for the L-88/ZL-1. It’s interesting to see that this characteristic carried through to 1970 for the LS-7. A remnant of its initial HD engine ties perhaps?

Ignition shielding distributor box and braided wires. The pilot LS-7 had a radio, no 1967-1969 L-88 (or ZL-1) could be ordered with one. A further indication that this was a street car.

Short dipstick, for what it’s worth.

I edited this post to add one more thing. I just noticed that the wiper door vacuum actuator is the double “pie pan” configuration as opposed to the more common (for 1969) cylindrical version that was used for most of 1969 production. The change occurred about mid October 1969 which works with a late October 1969 build date for the car.

Very good photo, Pat, thanks for posting it!

Regards,

Stan Falenski

[Joe L.]

Re: 1970 LS-7 engine

The collapse of the plans for various 454 engines for Corvettes in the face of new emissions requirements and the burden of certification testing of all engines to be used in 1970 Chevrolets is an interesting bit of Corvette history. We know that the original plans called for 454 versions of the L-88, ZL-1, L-68, L-71 and L36, under the names LS7, LT2, LJ1, LJ2 and LS5. Various GM documents and other sources, not just the parts book, are necessary for the understanding of what happened. The 1970 AIM has remnants documenting the successive cancellations of most of the planned engine lineup and the change in the LS7 body from the high L88 air induction hood to the regular big block hood with LS/7 decals. The CF thread whose link I supplied earlier has a time line for these events. The L-88 versions must have been the first to go. There was little chance they could pass emissions testing and little pay off for the effort even if they could. The culmination of these actions is represented in the early 70 sales brochure. There is the base LS5 and the 460 hp aluminum head LS7 without the accompanying F41, J56, air induction hood, radio restriction or 12.25 CR that would be expected of the original LS7 race engine. The LS7 nomenclature was now being used for a special high performance street engine not a HD race engine.

The Chevrolet Service News dated March 1970 was a supplement to the 1970 Chassis Service Manual for 1970 Corvette information because the 70 Chassis Manual retained 69 Corvette info (since 69 Corvettes were still in production). This supplement described the new SHP LS7 as 11.25 CR with a vacuum secondary 780 cfm Holley and an idle speed of 750 rpm with manual trans or 700 rpm with automatic. It also still listed the oddball street mechanical cam with .520/.550 gross lift.

The March 1970 service information was consistent with the January sales brochure and the pilot LS7 car presented to the press at the 1970 Corvette and Camaro introduction at Riverside CA. If any remnants of the HD race engine remained in the 1970 parts book, I suspect that was Duntov's effort to do racers a favor, and the pistons were the only new part. Duntov must have expected the fall back SHP LS7 to make it through the regulatory hassle since it was nearly identical to the Chevelle LS6 engine in production by this time. Here is a picture of the SHP LS7 engine in the pilot car.

Patrick------


Do we know the suffix code of this engine?

[Patrick B.]

Re: 1970 LS-7 engine

No. We do not.

[Bill B.]

Re: 1970 LS-7 engine

Very interesting and detailed information! Thanks all!!

While we may not know the code of that pilot car engine, the 1970 Historical info package from the GM Heritage Center has a section that is placed before the AMA section, titled "Serial Numbers and Identification". In section General-3, dated February 1970, it lists the intended production "454 RPO LS7" as "CZL" for the 4-speed and "CZN" for the Turbo Hydra-Matic.

[Mark E.]

Re: 1970 LS-7 engine

How did Chevrolet define HD and SHP?

L88 and ZL-1 are HD, so is this the racing only designation?

While SHP like L78, L71, L72 is suitable for street?

[Duke W.]

Re: 1970 LS-7 engine

Heavy Duty was Chevrolet's euphemism for RACING in order to not get in trouble with the 14th floor "no racing" edit.

Special High Performance means a high performance carbureted road engine. Most were mechanical lifter, but a few were hydraulic lifter like L-79, L-46, and L-82.

Duke

[John H.]

Re: 1970 LS-7 engine

In 1977, I bought a 69 coupe that had the 427 removed and an LS7 installed. The engine came out of the OKC assembly plant and supposedly was a balanced motor. It was a 454 but with cast iron heads, not aluminum. It had a low rise aluminum intake. Compression was around 13 to 1 and the engine never made enough vacuum to operate the wiper door. This engine was a beast. I had to run an AV gas mixture. I set it up to 1/4 mile but then had to leave town to finish my degree. I sold it in Springfield, MO in 1979. I put in 4:11 gears and a Morosa rear end. The car would pull the front wheels if you did a burnout with water. I believe it was closer to the L88 then to an LS6. Not sure where the car is today. I don't recall the pad stamp or engine numbers. I was 21 and had a good job with disposable income so I bought it to go fast. No pics.

[Joe L.]

Re: 1970 LS-7 engine

In 1977, I bought a 69 coupe that had the 427 removed and an LS7 installed. The engine came out of the OKC assembly plant and supposedly was a balanced motor. It was a 454 but with cast iron heads, not aluminum. It had a low rise aluminum intake. Compression was around 13 to 1 and the engine never made enough vacuum to operate the wiper door. This engine was a beast. I had to run an AV gas mixture. I set it up to 1/4 mile but then had to leave town to finish my degree. I sold it in Springfield, MO in 1979. I put in 4:11 gears and a Morosa rear end. The car would pull the front wheels if you did a burnout with water. I believe it was closer to the L88 then to an LS6. Not sure where the car is today. I don't recall the pad stamp or engine numbers. I was 21 and had a good job with disposable income so I bought it to go fast. No pics.

John-----


What is the "OKC" assembly plant and how did you know that?

[Tom P.]

Re: 1970 LS-7 engine

John-----


What is the "OKC" assembly plant and how did you know that?

I agree, what is the OKC plant! I've been here all my life and the only OKC plant was the automobile plant next to Tinker AFB (where I retired). In the beginning, the plant build Citations and Phoenix cars, and trucks in later years.
BUT, TO THE BEST OF MY KNOWLEDGE, no type of engine was every built at the OKC plant.
Additionally, many years ago, there WAS a GM parts warehouse located on the corner of Sante Fe and NW 36 street. The building is still there, but no longer used by GM. As I understood it, all the GM dealers (Chev, Pont, Buick, etc) got their parts through that warehouse.
And last, there was a GM tech training center in OKC for many years on N. I-35. that building still exists, but no longer associated with GM.
This is the old GM tech center building.

[John H.]

Re: 1970 LS-7 engine

I bought the 69 from a sales mgr at my local GM dealership. He had taken it on trade for a small airplane and wanted to sell it. The car came out of OK, not sure what part. The OKC plant story was second hand. The engine could have come over a parts counter but the seller maintained the engine was "balanced and blueprinted". It sounded good and came from a "car salesman" so who know. This was 46 yrs ago so I may not remember correctly but the engine was real. I had a professional GM mechanic run the engine numbers. Don't ask me what they were. In 1978 I didn't care about the numbers. I just wanted to go fast, drink beer, and date a few girls.

[Tom P.]

Re: 1970 LS-7 engine

Since 1970, there has been innumerable comments, discussions, debates, disagreements and speculations regarding the aborted LS7.
First, if any, how many were built?
(somewhere I have one of those 1970 brochures that lists the LS7 as an option for the 70 Corvette----------never built)
Did it have-----------or was it supposed to have------------iron heads, alum heads, alum block?
What was the comp ratio?
What was the HP rating?
And on and on and on.
SOOOOOOOOO, what's the true story? I doubt that anyone really knows.
At one time you could buy an LS7 from the parts dept. They had iron heads. John Neas bought 4 and has sold 2 of them.

[Bill B.]

Re: 1970 LS-7 engine

You are right, Tom, does anybody have the real scoop of what was intended for '70 production (and backdoor activity delivery)? One person who MAY know, still alive (last I knew), is Herb Fishel. I believe he worked with Zora around that timeframe as young engine development engineer. Herb eventually went on to become Director of Chevrolet Racing, then Executive Director of GM Motorsports. Last I knew, he was going to write a book on his experience at Chev/GM. If anyone might know some history there, it would be Herb. I had attempted to contact him via LinkedIn several years ago, but no joy.

[Stan F.]

Re: 1970 LS-7 engine

Since 1970, there has been innumerable comments, discussions, debates, disagreements and speculations regarding the aborted LS7.
First, if any, how many were built?

Certainly, one that we know of.

(somewhere I have one of those 1970 brochures that lists the LS7 as an option for the 70 Corvette----------never built)
Did it have-----------or was it supposed to have------------iron heads, alum heads, alum block?

Iron block, aluminum heads for the 1970 production version, iron block, iron heads for the parts department version released in 1973.

What was the comp ratio?

11.25 to 1 for the production version, 12.00 to 1 for the parts department version.

What was the HP rating?

460 or 465 for the production version (depending on what point in time you are considering). There was never a rating listed for the parts department version.

And on and on and on.
SOOOOOOOOO, what's the true story? I doubt that anyone really knows.

Actually, it’s pretty clear. There was a single example built by Chevrolet with the LS-7 engine. It’s documented in two magazines. With a few exceptions, we have a pretty good idea what it is. We may not know what it started out as, but we do know what it ended up as.

At one time you could buy an LS7 from the parts dept. They had iron heads. John Neas bought 4 and has sold 2 of them.

I would agree with you… Parts department LS-7… Iron block and heads.

Is Gib Hufstader still with us? He’s the one person mentioned in the magazine articles who would probably know all the details of the pilot car.

Regards,

Stan Falenski

[Tom P.]

Re: 1970 LS-7 engine

Too bad there was never a PRODUCTION all alum LS7.
Seems kind of strange none were built, since there were at least 71 all alum ZL1 engines built and sold to the public (69 ZL1 69 Camaros and 2 ZL1 69 Corvettes).
UNFORTUNATELY I do not have any pictures, but at one of the annual Chevellabration events (maybe about 2008???) someone had a 1970 Chevelle with an all alum 454 (GM alum block and heads). The APPEARANCE was as factory as you could get. Seems like (but I cannot remembe for sure) it was also a factory air cond car. Regardless of real or built, that would be the car to have today!!!!!!!!!!! And, with all that said, if I had the financial ability, our 70 Chevelle convertible would have an all alum 496. Oh well--------------------

[Patrick B.]

Re: 1970 LS-7 engine

The mystery and confusion about the LS7 is simply a matter of GM using and reusing the same name for two different engines. In the plans way in advance of the 70 model year, the LS7 name was given to the 454 successor of the L88. Several other 454 engines were planned and given names like LJ2. In the face of 1970 EPA requirements and the manpower needed to certify compliance, all of the planned 454 engines except the LS5 fell by the wayside in a messy way documented by a series of changes and cancellations still residing in the 70 AIM. The last effort to provide a SHP 454 was a new engine that had not been named in the earlier 1970 plans. It was a simplification of the LJ2, removing the 3X2 carb setup, and was nearly identical to the already certified Chevelle LS6 with the addition of closed chamber aluminum heads. At the time the sales brochures and the supplement to the 1970 Chevrolet Chassis Service Manual, both describing a SHP street engine, were written, it needed a name. GM simply recycled the LS7 name for it since the 454 L88 was gone. Unfortunately, the SHP LS7 was never certified either and was cancelled after one prototype had been manufactured and displayed to the press. Later, when the 454 race parts were being sold by GM Performance, they recycled the LS7 name again since the aborted SHP 454 was gone too.

The process was sloppy and traces of aborted plans for both engines can be found in GM documents. I am sure they would be surprised that super enthusiasts like us would find this a subject for debate 50 years later.