LS6 and LS5 Engines

[C3Vette Lady]

Is there any obvious difference in appearance between the LS6 and LS5 engines? How can I tell when I am looking at one if it is for sure a LS6 if the numbers don't match? Do they both have square ports? Thanks!

 

[C3Vette Lady]

LS6 & LS5 Engines

I was referring to LS6 & LS5 engines in C3s, by the way...

 

[RalleyRed]

LS5 has an iron intake and heads

LS6 had an aluminum intake and aluminum heads / with open chambers

I wish I could tell you if the ports were square, I really don't know.
But my guess would be either square or rectangle.

The LS6 also had mechanical lifters (solid lifters).

Very rare car indeed, my book also says that there was no fan shroud and the radio delete plate, both easy to duplicate.

The numbers on the heads and casting dates will help you, but without the stamped numbers to identify the block I don't know how you can be sure what your looking at.
I believe you could buy those heads as a service item over the counter from GM.

Good luck,

Rick

 

[C3Vette Lady]

LS6 vs. LS5

Thanks Rick. My stingray supposedly has an LS6 in it and just wanted to be able to "see it" to know for sure.

 

[RalleyRed]

Lanelle,

Interesting name, one of my sister's name is Janelle more common by far.

You do know that the LS6 was only offered in 71.

Have you checked the casting date on the rear of the motor by the bell housing passenger side.

So you do have the aluminum heads? Next time you have the valve covers off you can check those for date codes too.

If it's an original LS6 that motor is worth an awful lot of money to someone with a documented 71 LS6. Either way it's an awsome motor.
There were only 188 Vettes equipped w/ this motor in 71 only.

Nice find!!

Rick

 

[C3Vette Lady]

LS6

Hi Rick,

I bought this '73 with an LS6 engine in it. Obviously numbers don't match, but it's awesome 'cuz it's fast, 4 speed, big block, and doesn't have to pass smog!!! Ewwwww hoooo!!! ASAP I want to put a 3/4 cam in it too. Already ordered my custom plates for this one: VETRESS Guess I can get by without a blower....lol! This will be my speed toy and my '81 will be my "purdy" daily driver.

If you check the specs on this site for 1970 models, you will find that the LS6 was offered as an option. I was told when I bought it that the engine was from a 1970. Yep, the heads are aluminum!!!

So what is special about the LS6 besides pony power? (Let's see if I can get more happy than I am!!!)

 

[C3Vette Lady]

LS6 Torque?

Does anybody know how much torque the LS6 came with???

 

[C3Vette Lady]

LS6 Confusion

http://www.netvettes.com/1970.html

Oops, it was the website listed above that shows 1970 vettes having the LS6 engine as an option. It says 460 horsepower LS6 454 cu. in. big block tri-carbs.

According to CAC's model center, there is no LS6 listed for 1970 AND the LS6 for 1971 lists the pony power for the LS6 as only 425!

Have to admit I like the other site's h.p. listing better! haha! The guy I purchased the '73 Stingray from said it was a "1970 LS6/high performance top end" engine.

Dazed and confused....

 

[RalleyRed]

The LS6 was only offered in 1971.

The high performance 454 you refered to from 1970 was a LS7 and it never made it into production.
1970 was the only year that another GM had more HP than the Vette. The Chevelle super sport had a 450hp 454.
The most hp you could get in the Vette in 1970 was 390hp. (LS5)

Another thing they have wrong on that site is the 3 carb set-up aka Tri-power. This Tri-power was only available on the 67,68, 69's with either the 400hp or the 435hp Vettes.

Now I guess it is possible that GM offered the LS7 460hp motor as an over the counter item in 1970. You would really need to get those casting numbers I mentioned to know what year the motor was built.

Are there any numbers at all in front of the passenger side head?

You wanted to know what else is special about the LS6 other than the pony power..... nothing really. If I were you I'd crate it up and send it to me, I've got a nice 327 sitting here for you..LOL

Of course I joking!! If you get some numbers off the motor I'll help you figure out what you've got to the best of my ability and anything my book doesn't tell us I'm sure one of the other guys here will be able to help us with.

I'm sure that motor is a riot.

Rick

 

[C3Vette Lady]

LS6

Thanks Rick. I will get over to my mechanic's and look for that number. Dying to find out the info!!! What book is it you have that you keep referring to for looking up corvette info??

 

[RalleyRed]

Lanelle,

The book I've got is called

Vette-Vues

Factbook
of the
1968-1972 Stingray

Written by M.F. Dobbins

You asked about torque for the LS6

It's 475 ftlb's at 4000rpms

 

[C3Vette Lady]

Nos. off block to determine LS6 or what

Hey Rick,

I got the numbers off the block and on the passenger side they are M128 and on the driver side they are 14015445 then over a bit is G2P. Can you please look them up for me and tell me what I have?

Thanks a bunch and Happy New Year-
Lanelle

 

[BigBrakeFuelie]

There were LS6`s made and produced for the public in 1970.They were put in the Chevelle and listed at 450 Hp.In 71 they were put into the Vette and listed at 425hp.

 

[JohnZ]

The 14015445 block was used only in '75-'87 trucks - yours was cast on December 12, 1978. LS5's used the 3963512 ('70-'71) and 3999289 ('72), and LS6's ('71) used the 3963512.

 

[C3Vette Lady]

Engine Nos. off '73

Hey John Z,

Thanks for your info. Was wondering what the source of your info was and if ya got it out of a fact book? Any idea of the h.p. or torque? This engine has square port heads and aluminum intake. Maybe this is why my belts weren't fitting.....lol!

Thanks,
Lanelle

 

[C3Vette Lady]

Truck motor depression......

Well this has turned out to be pretty depressing if I have a truck 454 in my '73. Hope this isn't a hint of how the rest of my NEW YEAR is going to be.....ugh! :cry

Lanelle

 

[BigBrakeFuelie]

I`m sure it has lots of torque.So it will still be very effective for usable power.I thought about putting a 383 stroker in mine basically a truck engine.

 

[Tom Bryant]

Just because the block started life as a truck motor doesn't mean that it hasn't been built to LS6 or a higher performance level. All truck and low performance big blocks used oval port heads. Only the Special High Performance (396ci/360, 375and 425hp, 427ci/425,435 and 450hp, 454ci/425 and 450hp) and H.D. big blocks (L88, LS7) used the rectangular port heads that you are calling square port. Aluminum rec port heads were available on L88, L89(435 hp w/ aluminum heads), ZL1, 1971 LS6 and listed as optional on some late '60s 375 horse 396s in Camaro although I have never actually seen one. The other aluminum head listings were for 1970 LS6 and LS7 intended for Corvettes but didn't make it to production. Over the counter LS7s had iron heads. Some of these engines were not avavaible in Corvette. Most were grossly underated in their published factory horsepower ratings. Some of these engines could be bought over the counter as complete assemblys and all of these engines could be bought as partial assemblys and pieced together to complete engines from the parts department at your Chevy dealer.


To find out what you have you will need to contact previous owners to find out just who built the engine and what parts, GM and aftermarket, were used. The big difference between the Chevelle 450 hp LS6 of 1970 and the Corvette 425 horsepower LS6 of 1971 is that the compression ratio was lowered for 1971 and aluminum heads replaced the 1970 iron ones for a lighter weight in the Corvette.

Read this thread for more discussion on the LS6. I don't recall right off the top of my head what the torque ratings for the LS6s were but that doesn't do you any good until you know what parts are actually inside your engine.

Hope you are sucessful in contacting the person that built your engine.

Tom

 

[tonyk72]

Lanelle, just curious as to what made you think you had an LS-6 in the first place? Did you just recently purchase this 'vette and the seller told you it had an LS-6 motor? I know I'd be fumin' if that was the case...

 

[JohnZ]

Re: Engine Nos. off '73

Hey John Z,

Thanks for your info. Was wondering what the source of your info was and if ya got it out of a fact book? Any idea of the h.p. or torque? This engine has square port heads and aluminum intake. Maybe this is why my belts weren't fitting.....lol!

Thanks,
Lanelle

Lanelle - I have many different sources I've accumulated over the years that I cross-check, but I depend primarily on the NCRS Spec and Technical/Judging Guides, which are more accurate than any of the other reference books out there.

As Tom said, all hot 454's start from essentially the same basic block, and a truck block is an excellent foundation for a built-up engine. Your top end (heads and intake) are hi-perf items, and whoever built the engine (if you can find him) or the previous owner should be able to tell you what other pieces are in it. Just enjoy it and don't worry about the "numbers".