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71 LT-1 vs. 72 LT-1

J

jmp

Guest
Hey all!

Just wondering if someone could fill me in on the differences between the 71 and 72 LT-1s? Or at least point me to a site that describes the differences?

Thanks!
 
7

72LT1Steve

Guest
Joseph;

Differences between the two years is not much. Fiber optics were gone in '72. With the alarm system now being standard. '72 LT-1's engines were rated at 255HP as compared to '71 where they were rated at 330HP. This was not due to any mechanical change, but more because of rating criteria. In '72 horse power was "net" rated at the rear wheels rather "gross" rated at the flywheel. Of course the interior console data plates reflected this different information as well.

In '72 Chevrolet began it's engine designation in the VIN number's. You should find an "L" designator in the 5th position for the LT-1 350. "K" would represent the base motor 350 and "W" for the 454 motor.

'72 was the only year that air conditioning could be ordered with the LT-1 package, and this was for only about 1/2 to the last 1/3 of the year or so, with approximately 240 cars being so equipped. In conjunction with this option, the standard 6500 red line tach was not used, but replaced with a 5600 red line tach. The front turn signal lenses were amber in '72 and clear in '71. I have heard of some '71 cars having amber lenses as well, but have'nt seen a any to date.

And finally paint colors options changed somewhat, with five of them changing (at least name wise).

Hope this gives you some idea.

Take care Steve
'72 LT-1 Roadster
 
R

RalleyRed

Guest
I agree with everything Steve mentioned bar one,

And I maybe wrong, but I don't think so.

Both motor's were rated at the flywheel, the difference was that the 72's up ( all the accessories mounted as were the muffler's )

While the earlier car's had none of this to steal HP.

Both are very nice Vette's.

Rick
 
D

DkBG

Guest
Your both right ! Your saying the same thing in different ways .
 
R

RalleyRed

Guest
DkGB,

I believe there is a difference between measuing hp at the flywheel and measuring it at the rearwheel's.

Again, I'm rarely sure of anything these day's but I don't think they had chassis dyno back in 72.

Please correct me if I'm wrong.

:upthumbs

I'm alway's willing to learn new stuff.

Thank's,

Rick
 
I

inferno-vette

Guest
I'm sure that Steve is right because If you dyno an engine at the flywheel and then at the rear wheels you can see a difference of 20-25% loss due to the drive train........in this case 330 gross hp-23%= 255 net hp.
Paul
 

rainman

Well-known member
Joined
Feb 23, 2002
Messages
130
Location
San Diego, CA
Corvette
02 Z06, 65 L-76
The 1971 Chevrolet sales broshure for the corvette listed both gross and net hp for all four engine options. The broshure shows the LT-1 for that year with 275 net hp.
 
J

jmp

Guest
torque

I'm a little confused about something... On the plate on the center console of my 72 LT-1, it lists the torque as 360 ft/lbs. But I've seen 72 specs on the web listing the torque as 280 @ 4000 rpm. I'm going with what my car says! And I guess I'll check the heaps of manuals that came with the car when I get home tonight, but if someone else can chime in here...
 
J

jmp

Guest
torque answer

Ok, it turns out both figures are correct. The 360 number is gross, while the 280 is net. This according to Motor Trend's June 1972 issue. This issue also says that the gross hp rating for the 72 LT-1 is 330 (net 255).

Here's some performance stats:
0-30 2.9
0-60 6.9
1/4 mile 14.3 @ 92 mph
Gas Mileage 9-12 mpg

WTF? The gas mileage for the 454 is 13-15 mpg! That's better than the base 350 too!
 
G

gdh

Guest
I concur with the above stats. and on a long trip last year I averaged about 13 mpg.
 
0

0018

Guest
jmp said:
Hey all!

Just wondering if someone could fill me in on the differences between the 71 and 72 LT-1s? Or at least point me to a site that describes the differences?

Thanks!
 
Joined
May 29, 2002
Messages
8,652
Location
Missoura Ozarks
Corvette
2012 💯 4LT GS Roadster
Sounds Like the 71 LT-1 had the Stuff ! :r
 
0

0018

Guest
jmp said:
Hey all!

Just wondering if someone could fill me in on the differences between the 71 and 72 LT-1s? Or at least point me to a site that describes the differences?

Thanks!
 
0

0018

Guest
Having owned all 3 years of LT-1s, the 1970 is without a doubt the fastest. Rated at 370 H.P., this high compression small block put out over 430 horsepower. The 370 H.P. rating was an insurance dodge. Government emission regulations eventually killed the LT-1. The Compression ratio was reduced from 11:1 to 9:1 in 1971 to be compatible with the new unleaded gas. Ignition timing was reduced from 12 degrees advance, to 8 degrees on the '71s, to 4 degrees on the '72. Valve timing was also retarded to meet the new emission laws. The LT-1 was becoming "too tame" to carry on the legend it started in 1970. I personally am glad Zora decided to pull the plug on the engine he wanted for so long. I would hate to see the anemic engines of the mid and late '70s being badged as LT-1s. I have heard of early '71 LT-1s being equipped with leftover '70 high compression engines. All three years are great cars, and worthy of the LT-1 designation. Unfortunately Uncle Sam and the environmentalists had to put a damper on our fun. Maybe its a blessing in disquise, if the LT-1 was to become a common Corvette, like the L-82, that wouldnt be much fun either. Drive 'em. Drive 'em hard! Thats why Zora built 'em in the first place....FUN!!!
 
0

0018

Guest
inferno-vette said:
I'm sure that Steve is right because If you dyno an engine at the flywheel and then at the rear wheels you can see a difference of 20-25% loss due to the drive train........in this case 330 gross hp-23%= 255 net hp.
Paul
 
0

0018

Guest
Re: Re: 71 LT-1 vs. 72 LT-1

0018 said:

The 1971 LT-1 had more poop than the '72. More horsepower too, however you measure it. Not to mention the Transisor Ignition, and advanced ignition and valve timing. Like the Packard ad used to say "ask the man who owns one." Ive owned 'em all and the 1970 is the fastest. I presently own an original Ontario Orange '72 coupe with 49,000 actual miles, and love every inch and ounce of it!! (But I must admit, its the slowest LT-1) as if it really matters. Its still too fast for a 48 year "kid" after a few cold ones, so I call a taxi. Cab Drivers are more understanding than my wife. So who has a '70 LT-1 Roadster for sale??
 
Joined
May 29, 2002
Messages
8,652
Location
Missoura Ozarks
Corvette
2012 💯 4LT GS Roadster
330 HP with 10.8:1 compression and a 6,300 RPM Redline . . .

That's why I like the LT4 so much, push the petal down and let them ponies go !!! :_rock
 
0

0018

Guest
rainman said:
The 1971 Chevrolet sales broshure for the corvette listed both gross and net hp for all four engine options. The broshure shows the LT-1 for that year with 275 net hp.

The 275 net hp seems about right for a '71 LT-1. 1971s are noticeably a tad faster than the '72, which is rated at 255 hp. There are minor differences between the two engines. The '72 had decreased ignition and valve timing to meet the ever tightening government emission regulations. Also the transistorized iginition was discontinued on LT-1s in '72. The big horsepower reduction took place the year before when the high compression '70 engines were detuned to be compatible with the new unleaded fuel which was to replace leaded fuel by the mid '70s. With the introduction of TPI fuel injection in 1985, horsepower started its upward trend, which now is in excess of 400 hp. Way to go guys!!
 
W

wagonmaster

Guest
Net VS. Gross H.P.

Ok guys here it is.... The '71 was rated with the old Horsepower method. That was flywheel dyno horsepower with NO loss for water pump, alternator, smog pump, etc. '72 was the very first year that the "net" method was used for torque and horsepower. This was a "real world" figure that all the cars would generally meet that factored in all those frictional losses, but was NOT rear wheel horsepower. We surely DID have chassis dynos then, but they weren't used for this. I sold these new in '71 and '72 and was really crushed about the H.P. rating system.
Kinda makes you understand why the new 350 h.p. Corvette is so much faster that the "oldies" with 350 h.p. doesn't it?
The saddest part of all this to me is that the LT-1 would pass the more stringent '73 emissions, but the feds wouldn't allow Chevrolet to adjust the valves at 50,000 miles, and they tested emissions to that point on the test "mule" vehicles from all the manufacturers. If they had allowed the adjustment, we could've had them two more years anyway. ('75 was too tough even with the adjustment) Hope this helps. :upthumbs :beer
Joe
 

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