Hi, I have a '71 big block that did not come with the original motor (had a small in it) trying to restore car to original condition.  The inside dash says 454 425 horse which would make it an LS6.  I would like to what else I can do  to verify that it is a LS6.  I looked for bill sheet by gas tank and did not find one.  It also has a rear stabilizer bar.  Does this indicate it might be a ZR2?  I would like to find out if I need aluminum or cast heads, keep getting mixed info on that.  Any help would be appreciated.   Thanks

The 1971 Corvette would develop into a more balanced -- though tamer -- performer as the Seventies wore on and the engineers came to grips with the flurry of federal regulations before them. Due to a decrease in compression ratio for 1971, the 1971 Corvettes's base small-block engine ran on mild 8:5:1 compression and was down to 270 bhp at 4,800 rpm. To this end, the potent LT1 small block withered to 9.0:1 and dropped from 370 bhp to 330 bhp. These respective compression numbers also applied to a brace of 454s. The LS5 came in with 365 bhp at 4800 rpm, and a new aluminum-head big-block called LS6 boasted 425 bhp at 5,600 rpm. Clearly, 1971 Corvette engines weren't weak. If they seemed so at the time, it was only in relation to the prodigious power outputs enthusiasts had grown used to in the previously unregulated era of muscle cars.

The ZR1 option available exclusively with the LT1 is significant for engineering, though not many saw production. It was a special racing package that included the solid-lifter small-block engine, heavy-duty four-speed transmission, power brakes, aluminum radiator, and a revised suspension with special springs, shocks, stabilizer bar, and spindle-strut shafts. Since it was competition equipment, the ZR1 could not be ordered with power windows, power steering, air conditioning, a rear-window defogger, wheel covers, or a radio. But the ZR1 package was quite expensive, and few Corvettes were so equipped.

A similar ZR2 package was listed for the big LS6 engine and was just as rare. Per GM policy, 1971 Corvette engines were detuned to run on low-lead fuel -- save the LS6 454, which belatedly bowed with 425 bhp on premium gas. Installations totaled just 188, including a mere 12 cars with a $1,747 ZR2 package, basically the ZR1 with the big-block V-8. This would be the only year for both the LS6 engine and the associated ZR2 equipment.

corvette440hp2009-02-02 08:36:09

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Paul, it did use aluminum heads on the LS6.

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Here is the complete article........  http://auto.howstuffworks.com/1971-corvette.htm corvette440hp2009-02-02 08:40:52

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All big blocks had a rear stabilizer bar, but the ZR2 option would have been larger than "standard".
The LS6 did have aluminuminum heads.
What is the tach redline?
What trans does it have, or has that been changed also?
The ZR2 would not have an auto trans.
LS6s would also have HD brakes, transistor ignition, aluminuminum radiator, metal fan shroud, but no power windows, no rear defog, no A/C, no power steering, no radio, and no alarm system.
hth
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(dang...guess I should've read Larry's post a little more closely...) Adams' Apple2009-02-02 08:52:48

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Joel Adams
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The 71 LS6 did opt. power steering. If you look on the frame, right behind the drivers side rear tire, on top of the frame, there will be a number stamped into the frame. This should match the V.I.N. I have a 71 convertible LS6. If you want to E-Mail me Randrighetto@aol.com perhaps I could help you with info.

I have a LS6 vette. E-mail me @randrighetto@aol.com