Ls7

[Tag W.]

Re: Ls7

I leave to tend to Thanksgiving preparations and come back to some great info and comments.So as I understand it it was possible that an LS7 was used as warranty replacement(in some form).This was in early 1970's as I understand.Thanks everyone

[Terry M.]

Re: Ls7

I leave to tend to Thanksgiving preparations and come back to some great info and comments.So as I understand it it was possible that an LS7 was used as warranty replacement(in some form).This was in early 1970's as I understand.Thanks everyone

Remember Tag -- it is not the original motor, regardless of how desirable the replacement might be. To some folks, and maybe you, that doesn't matter, but it will reduce your or your heirs' pool of buyers when that time comes.

[Clem Z.]

Re: Ls7

back in the 70s sunoco 260 was available and you could run engines like the LS-7 on the street but now you would need racing gas because of the 12.5:1 CR.

[Joe L.]

Re: Ls7

I leave to tend to Thanksgiving preparations and come back to some great info and comments.So as I understand it it was possible that an LS7 was used as warranty replacement(in some form).This was in early 1970's as I understand.Thanks everyone

Tag------

The 1970 LS-7 engine assembly was available in SERVICE under GM #3965774. Although this is a late 1969 part number, I cannot find that it was actually available in REGULAR SERVICE until ABOUT 1975. So, it's possible that it was an earlier unused part number that was "plucked out" and assigned in the mid 70's OR it's possible that it was available prior to that time through some special parts channel. I don't think that warranty replacement would have been one of them, though. Since the engine was never available in PRODUCTION, GM would have had no reason to make it available as a warranty replacement. That's not to say that it could not have been used for warranty replacement but, if so, I would say that it would have to have been supplied through regular SERVICE channels. So, now we're back to it's first SERVICE availability about 1975.

But, it gets even more complicated. The original 1970 LS-7 was to have included aluminum cylinder heads, the same ones used for 1969 L-88. However, the GM #3965774 LS-7 engine assembly had cast iron heads. Otherwise, though, it was pretty much configured as the original LS-7 engine assembly would have been if it had been released. The suffix code for the 3965774 engine is "XCH"

I think there's a very good possibility that 1970 Corvette LS-7 engines, as they were supposed to be originally configured, were manufactured in the late 1969-early 1970 period and of some part number unknown to me. Just what happened to these engines, assuming they were actually manufactured, I have no idea. I do KNOW that a partial engine assembly ("short block") was manufactured and available under GM #3981824. The "window" of availability of this piece was very short, though---from ABOUT February 1970 until January, 1971.

Notwithstanding the above, a lot of the "mystery" behind the engine you are referring to can easily be solved. Simply check for the block casting date. The block has to have such a date and it should be found on the bellhousing flange. Also, if the engine was originally supplied as a complete engine, there should be a stamping on the block stamp pad on the front of the right side cylinder bank OR on a small machined area just above the timing cover. Report this information and the picture might become a lot clearer.

[Dick W.]

Re: Ls7

A little off topic, but I do know of one '69 L/88 that has been around the show circuit that has a homemade LS 7 in it. '69 512 block with 454 crank and LS-7 pistons. Virtually undetectable. One stout ride

[Clem Z.]

Re: Ls7

A little off topic, but I do know of one '69 L/88 that has been around the show circuit that has a homemade LS 7 in it. '69 512 block with 454 crank and LS-7 pistons. Virtually undetectable. One stout ride

i know were there are a couple of them one new and one used. the used one was taken out of a friends chevelle when he could no longer get gasoline to drive on the street and he put the 396 back in. another one is under a guys work bench never fired.

[Graeme B.]

Re: Ls7

Many years ago I had a 69 L-71 (my first one) and the engine seized a piston. The engine was replaced under waranty with a LS-6 as the owner knew the Dealer. Motor was stamped on the pad CE xxxxx.(can't remember the number offhand.

[Michael H.]

Re: Ls7

[quote=Clem Zahrobsky (45134);523277]

we can also add the words "cylinder case" to add to the confusion.

GM also refered to this as a partial engine assy or 1/2 engine assy. Occasionally the block was refered to as a "cylinder and case assembly.

We just called it a short block.

[Michael H.]

Re: Ls7

Tag------

The 1970 LS-7 engine assembly was available in SERVICE under GM #3965774. Although this is a late 1969 part number, I cannot find that it was actually available in REGULAR SERVICE until ABOUT 1975. .

Joe,

I think I have some GM info on the 3965774 engine assembly that was dated at least two or three years earlier than 1975. The first info released to dealers came in a multi page flyer called "Hotline". The first one that I remember for the LS7 was titled "Horsepower To Burn", and it described the assembly and it's components.

In 1971 or 72, I was told that when GM nixed the LS7 option for production cars, the existing engines were stored in a separate warehouse somewhere. Eventually, they were to be sold through P&A at a very reasonable price until all were gone. For some reason, GM decided to continue producing the LS7 engine for over the counter (so to speak) sales.

The earliest information I had about the new LS7 was in late 1970. A group of high perf/HD parts in that 3965XXX part number range were released at the same time.

Add On: Found one dated 25 July 73. It lists absolutely every part and part number used to assemble an LS7 engine including the cyl head and clutch housing dowel pins, block coolant and oil gallery plugs, oil pan bolts etc etc. Many items that were never listed in the parts book.
I know I have earlier Hotline sheets and other GM info that describe the LS7. I'll look.

[Terry M.]

Re: Ls7

There was also a "fitted case" I believe that was the cylinder case and pistons, but nothing else. Yes, if certainly can get confusing.

[Chuck S.]

Re: Ls7

...In 1971 or 72, I was told that when GM nixed the LS7 option for production cars, the existing engines were stored in a separate warehouse somewhere. Eventually, they were to be sold through P&A at a very reasonable price until all were gone. For some reason, GM decided to continue producing the LS7 engine for over the counter (so to speak) sales...

Warehoused engines that were originally intended for production cars should then be stamped with the conventional "machine stamp" that we know well wouldn't they? Unless, of course, the original machine stamps were ground out and the engines restamped "CE" before being released for over-the-counter sales.

I think John H said the CE stamp indicates the year of production...in the case of prestamped, warehoused engines, they would probably have used the year the engines were released for sale.

Tag, what's the machine stamp on this engine? (front right head/block interface area) That info, including the pad condition (whether ground and re-stamped or not) might provide more insight.

[Dick W.]

Re: Ls7

The crate engines destined to be sold by your local dealer had the typical machine codes stamped on them. Bare cylinder cases did not have anything stamped on them. I have blank 351 and 512 blocks with nothing stamped on them. I am unsure about the fitted blocks as to whether they were blank or stamped.

[Michael H.]

Re: Ls7

Warehoused engines that were originally intended for production cars should then be stamped with the conventional "machine stamp" that we know well wouldn't they? .

I don't know about the LS7, Chuck. I don't know if that engine ever had a code. If it did, and if Tonawanda actually assembled some for the car option, (that never existed) they would have had the typical Tonawanda source/date/suf stamp info.

If none were ever built for the 1970 model, and some GM notes indicate that none were, the engines assembled later would probably either be blank or have the CE stamp. Here's why I say none were assembled for production. A note in an internal memo, and eventually in the heavy duty pages of the parts book, mention something about "the LS7 engine being available for service only and those in existance were assembled using existing components". That leans toward saying that the LS7 engine assembly would be available until parts were depleted.
Obviously, some time after that, GM decided to continue making components to build/sell the LS7 for decades. I'll see if I can dig out that note.

My guess is that all LS7 engines built after about 1972 would have had the CE stamp.

Add on: Found it. In a GM paper dated 16 Nov 1970, there's a note that states.... LS-7 "454" Heavy Duty Engines were not produced on the assembly line. Those in existance were built-up from service parts.

[Tag W.]

Re: Ls7

Block casting#3963512,Machine stamp CE165673.Boy,you guys sure have a lot of old info,great education for me,thanks again for the replies.

[Chuck S.]

Re: Ls7

Block casting#3963512,Machine stamp CE165673.Boy,you guys sure have a lot of old info,great education for me,thanks again for the replies.

I believe the year of production is embedded in that CE number somewhere. Only someone that was on the inside at that time probably understands how to read the number. Maybe John H will see your thread and comment.

Regardless whether the engine was installed under warranty or not, as Terry said, it's not the original engine. If you're looking at this car as a potential purchase, then your dilemma is how to set a value on the engine/car package.

The engine alone is valuable; but, without the original engine (or even a documented warranty replacement), the car is devalued, maybe considerably. That's one motive for the seller to claim the LS7 was a warranty replacement...it allows him to maximize the value of the car.

Now if he also had the original engine, both car and LS7 engine would be valuable, separately or together. Without documentation, however, I would say it's pretty much a moot point...the warranty replacement story is an interesting anecdote you may not be able to change into cash when you need to sell. But, you would have a wild ride until selling time.