Ganey

The OTC 454 3965774 was not supposed to be the LS-7. There was another 454 listed same w/ lower C/R though not available 366250.

gtc131

Yes, the lead time for printing and distribution of manuals, brochures, etc, in the era prior to desktop publishing would have been quite long and as I understand it, the kill decision was made quite late into the production cycle.

From what I've read, the reasons for killing the LS7 production option at that time include: GM's policy of deproliferation of engine options across the board and the nascent push for fuel efficiency, but the one that strikes me as most likely is the hoo-hah created around that time by daily press jounalists about "muscle cars" in general panicking GM management which, by then, was essentially a cabal of corporate accountants anyway.

wer2xu

a cabal of corporate accountants...i like that...
When did GM acquire Holden?

CCrane65

Actually, the LS-7 never made it into a Corvette but there are some in Chevelles. That page above from Chevrolet Service News is not vehicle specific.

I've seen them listed as 450 HP but it was the same ruse they used for the L88.

cc

gtc131

The entire March 70 issue of Chevrolet Service News, apart from 2 sections on the back page, is devoted to the 1970 Corvette, and those 2 non-specific sections are "Servicing Propeller Shaft Front Slip Yokes" & "Auxiliary Battery Option - 1969-70 Camper Equipped Trucks".

The engine specs page is from Section 6.

gtc131

1931. Until then Holden Body Works made bodies for other manufacturers, including Ford.

Ganey

Actually the same engine in a Chevelle & others would make less hp due to the Corvette having the better exhaust.

Entirely different for L-88, HP was rated lower to keep the clueless (like .........) from ordering the highest HP engine.

CCrane65

I agree to some extent but really, 450? From what I've read it would be closer to 630 in a Chevelle and 650 in a Corvette.

The LS-7 was basically a replacement for the L-88.

450hp output is no better than the L89s in 1967 which were immediately re-labeled 435.

The most you give up to exhaust is 15-20 hp.

cc

Ganey

A high power BB loses a lot more than that w/ manifolds instead of headers! The nos. you have are too high.

OTC crate "LS-7" 12 C/R on dyno w/ headers
HP 489 @ 6000
TQ 481 @ 4000

CCrane65

Yes but, we weren't talking about headers, the OP was saying the previous owner built it as factory installed with per 1970 Chevrolet specifications.

The guy modified the crate engine.

cc

68/70Vette

..Noticed that two of the postings alluded to the LS6 or LS7 being gas gusslers.

I built a piece part L88 with the only modifications being that I had the piston domes milled down to lower compression from 12.5:1 to ~11.5:1The engine delivered good gas mileage numbers. However, I did have a 3.08:1 rear end diff ratio. I could drive to Las Vegas on one tank of gas, and have some left over. owever, the L88 cam and 3.08 made the car difficult to drive on the street since it had such low torque at low engine rpms. After coming for a stop at an intersection, it took a lot of clutch slip to get the car rolling. This streetability problem was solved with a Richmond 5 speed (then sold as a Doug Nash 4+1).

TheSkunkWorks

Seems to me, one reason the LS6 or LS7 would guzzle more gas than an L88 is that 0.25" longer stroke.

wer2xu

and the fact that I am trying to teach myself how to tune a holley.

gtc131

With the 3.08 rear and M22 box I am getting worst 4.57 US mpg (!!!!) best 14.74 US mpg. It runs 98ron premium fuel.

I have had the (now hydraulic) clutch replaced to McLeod Street/Strip and that's quite heavy underfoot. Yes, launching is a bit wild and the cam doesn't like city traffic, but on the highway it's a great car to drive.

I should add that cooling is not an issue. It still has the original GM clutch fan and shroud, albeit with 7 blades (no aircon).

gtc131

I gave up. I'm taking her in for a tune this very day.

TimAT

I feel your pain- I've got the M-22 with 4:11's on that crate LS-7 with the ZL-1 cam and aluminum heads topped with an 850 Demon. I'd get a woody if I got 5. And that's on VP 110 fuel.

I had problems with cooling over 70 MPH- got the year of manufacture plates which let me remove the front plate and bracket, and no more cooling problems. The factory L-88 radiator was installed in '71 with a piece/part shroud.

gtc131

I run an 850 Holley. My mechanic reckons it's overcarbed -- he wants to put a 780 on it -- but I like it like it is

I have never had overheating problems at any point. The guy who built the engine (i.e. the car's previous owner) was very proud of the fact that it runs cool as the proverbial cucumber. He is a stickler for the GM factory setup, including correct cowling and fender skirt sleeves.

I was on a Club run on Sydney's the hottest February day on record when it hit 44C (111F) in the shade, and the Vette just sat on 195 degrees all day, even when idling in the traffic. The other guys on the run with me could not believe it. In fact, a lot of guys, with small blocks, avoided the run when they heard the predicted temperature simply because they feared a boil over.

Plates-wise, I have the only type of NSW plate that will fit without bending:

AB73

Dont mean to hijack your thread gtc131 but like you I have tried tracking down the original factory specs for the crate LS7 with little luck. Even in this thread there seems to be inconsistant results, perhaps due to confusion between the two engines, the crate engine and the proposed option engine.

BTW nice to see another LS7 owner down this way.

Cheers
Tony

TimAT

Chevy put the 850 cfm carb on the L-88's. FWIW, I've had everything on mine from a 650 to a 2x4 setup that worked out just over 1200 cfm. The 650 was bad to the bone off of a stoplight, but ran out of air before 5000- labored hard to make 6500. 750 wasn't too bad- lost some low end and gained it back on top. the 850 is good - kind of a balance between not having low end torque and a really good top end. The 2x4's were unreal- great down low and would really come alive and pull hard.
I don't think 850 is too much for what you're running. Mine works real well overall. Maybe you need to work out some jetting or power valve issues?

Your front plate looks the same as what we run here. I never had any problems at low speed, just at hiway speed. And it wasn't anything bad- it'd just get up to 210.

gtc131

Yes, it's crossed my mind (briefly!) to research and write the "definitive" essay on the LS7, however without having access to GM internal documentation of the era -- especially inter-office memos where discussions between department heads can be overheard -- and without interviewing the people involved at the time, I'd be simply regurgitating the theories, myths and contradictions that we are already familiar with.

Cheers, mate!