m1982

Hi all
I just wanted to hear if any know how big a difference there is between the 1970 LS-5 high compression performance vs. 1971 LS-5 low compression. The 1970 model is suposed to have the highst torque of any stock corvette 500 at 3400 rpm. Is it right and how does it perform with the later 454´s.
Any info would be great, I have not been able to find any old mag-tests of the 1970 454 even not in the corvettearchive.

m1982

Are there no 1970 454/390 LS-5 people out there? :rolleyes: Or anybody that know of a test a 1970 LS-5? :seeya

1Bad69

according to corvette fever from june 1995:
Torque Horsepower
70Ls5-500 390
71Ls5-465 365
72Ls5-465 270
73Ls4-395 275
74Ls4-395 270
it did not list any 1/4 mile times or performance data..



[Modified by 1bad69, 1:43 PM 1/20/2002]

Turbo-Jet

dropping compression to 8.5:1 for 71 lost 25 GROSS hp. not that much.
my 72 makes 390 NET lb-ft of torque. the 500 lb-ft is not comparable to the 1972+ engine rating method.

livin

I read that the 71's drop in compression did not make a very noticeable difference on the street, and the drop in compression allowed the use of lower octane fuel. :)
I read that in 'Illustrated Buyers Guide', by Michael Antonick.

Turbo-Jet

correct. enlarging the chambers unshroaded the valves, which improved combustion efficiency. able to gain back some of the losses this way.

m1982

Anybody knows what kind of 0-60 times one could hope for with a 170 or 71 LS5. :cool:

zwede

You're looking at low 6's to high 5's.

70 Vette

Here is what I found in my archives:

1970 LS5 with auto trans and 3.08 gears, 15.00 sec quarter mile (Car & Driver, Sep 1970)

1971 LS5 with auto trans and 3.08 gears, 14.65 sec quarter mile (Car & Driver, Jun 71)

Of course driver ability, weather conditions etc can make a huge difference.

SuperFast80

No 1970 LS-5 :( but here are a couple 1971 and 1972 tests:

Car and Driver, June 1971:



Motor Trend, June 1972:

Chuck Harmon

When I saw this article again it amazes me just how fast the new Vettes are. In 1973, I thought the days of performance were over for good. I once wished that they would stop making Vettes (even though I would buy 3 more :)) because the new ones really watered down the performance reputation of the older ones. The new z06 Vettes are fully 3 seconds faster to 100 than this very quick shifting test was able to do, and still idle about as smoothly as an L48!

The 71 LS6 Vette really was one fantastic car. I just really wish they had released the 1970 version of the L89 and L88. With the extra 27 cubes and 4 barrel only, they were renamed LS6 and LS7. 1970 would really be the benchmark year today if they had!

Chuck

m1982

I think that only 98 octane pump fuel would be possible to get around here (Holland), so would that be allright for a 1970 LS5 with 10.25 compression? :confused:

70 Vette

From what I have read, you have two choices: either add the octane booster to your tank each time you fill up, or harden the valve seats and put in lower compression pistons. You'd want about 9.5 - 9.8:1.

Chuck Harmon

When they dropped the compression to make way for unleaded gas down the road, they only had the 87 octane of our regular unleaded in mind, not the 92-94 available today (except California :( ) Our gas used to be quoted in Research octane numbers, not the average of Research and Motor octane numbers as is required today. I believe they still quote just the higher Research number in Europe which is why it appears that they have better gas.

10.25 with aluminum heads on 92+ octane is not a problem on the street unless you are pushing the motor for an extended period. If you go to the track, fill up there with race gas. Unleaded gas has much less carbon build-up than the leaded gas. This helps avoid knock or ping for two reasons: (1) Less build-up means lower actual real world compression, and (2) no glowing charcoal briquettes inside the combustion chamber pre-igniting the fuel.

Chuck



[Modified by Chuck Harmon, 1:57 PM 1/23/2002]