70 vs 71 454
Thread Starter
Melting Slicks
Joined: Dec 2007
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From: Olivia mn
70 vs 71 454
hey guys, was just wondering if you can realy tell the performance differance between the two? Is there a differance I have only drove the 71 so thats why I am asking
Drifting
Joined: Oct 2007
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From: Brown Summit North Carolina
I can report that the 71 LtT1 had 40 HP less than the 70 LT-1 but in the real world ,on the street they both performed very close if the rear ratio were the same on both cars according to all I have read.
I assume the same can be said for the 454 cars.
As for value, the 1970 cars seem to bring more than 71 /72
This is due to things like very low production in 70 and the mystic of being the last of the high compression cars.
I assume the same can be said for the 454 cars.
As for value, the 1970 cars seem to bring more than 71 /72
This is due to things like very low production in 70 and the mystic of being the last of the high compression cars.
Melting Slicks
Joined: Nov 2003
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From: St. Charles Mo
CI 5 & 8 Veteran
I have owned two LT-1's. The 70 and a 72 which I recently sold. The 72 engine is identical to the 71 with the lower compression heads. The 70 with it's higher compression out performed the 72 hands down.
Bullshark
Safety Car
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From: Indy Indiana
I thought 71 was the 1st year when 'net' horsepower was the basis of the horsepower rating, wheras 70 was rated 'gross' horsepower.. yes several have said that the difference is negligible. Gross and Net are about 20% different due to factoring in the accessories such as AC and Power Steering in dragging the power output.. Correct me if I am wrong?
Melting Slicks
Joined: Nov 2003
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From: St. Charles Mo
CI 5 & 8 Veteran
I thought 71 was the 1st year when 'net' horsepower was the basis of the horsepower rating, wheras 70 was rated 'gross' horsepower.. yes several have said that the difference is negligible. Gross and Net are about 20% different due to factoring in the accessories such as AC and Power Steering in dragging the power output.. Correct me if I am wrong?
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Burning Brakes
Joined: Jun 2004
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From: Cortlandt Manor New York
The 70 was the last year of higher compression and minimal polution controls. Strictly stock the 2 factors made the 70 a better performing engine. That is not to say that you couldn't make some changes to a later model and improve it to perform the same or better.
Burning Brakes
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From: Kalispell MT
Drifting
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From: Brown Summit North Carolina
David
Team Owner
Joined: Jan 2006
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From: Crossville TN
Those three years [70, 71, & 72] are frequently a point of confusion as to HP numbers. Here's my attempt at a quick summary:
1970 was the last year for high compression engines; HP was rated with SAE gross method. 1971 had reduced compression engines (8.5 for base engines, 9.5 for hi-performance); HP still rated in SAE gross. 1972 used almost identical engines as 1971 BUT...they were rated in SAE net numbers [had to subtract the HP losses for auxillary equipment.
So, not only was 1970 a short-run model year, but it also had the highest horsepower engines possible. 1971's HP was down because of compression loss. 1972's HP was lower strictly because of rating method change.
1970 was the last year for high compression engines; HP was rated with SAE gross method. 1971 had reduced compression engines (8.5 for base engines, 9.5 for hi-performance); HP still rated in SAE gross. 1972 used almost identical engines as 1971 BUT...they were rated in SAE net numbers [had to subtract the HP losses for auxillary equipment.
So, not only was 1970 a short-run model year, but it also had the highest horsepower engines possible. 1971's HP was down because of compression loss. 1972's HP was lower strictly because of rating method change.
Melting Slicks
Joined: Nov 2003
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From: St. Charles Mo
CI 5 & 8 Veteran
Hope things are good for you also. Sorry, but I sold the 72 LT-1 to a friend here in St. Louis a few months ago. One of the St. Louis C3 sharks. It's hard enough keeping up with the ones I have now. 
He will give it a good home and it's still close by.Bullshark
Melting Slicks
Joined: Nov 2004
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From: Nevada City California
We need to correct some mis-information that has been stated above by previous posters.
Yes, there definitely is a difference between the three years that the LS-5 engine was offered as an option on the Corvette.
1970 LS-5 is 390 hp (gross) & 500 ft lbs of torque. Comp ratio is 10.25 to 1. Net hp is unpublished.
1971 LS-5 is 365 hp (gross) & 475 ft lbs of torque. Comp ratio is 8.5 to 1. Net hp is 285.
1972 LS-5 is 350 hp (gross) & 475 ft lbs of torque. Comp ratio is 8.5 to 1. Net hp is 270.
1970 engine uses TCS and re-calibrated distributor for emissions.
1971 engine uses CEC and re-calibrated distributor, for emissions.
1972 engine uses TCS and re-calibrated carburetor, distributor and A.I.R. emissions system. Timing specs are different from 1971.
Yes, there definitely is a difference between the three years that the LS-5 engine was offered as an option on the Corvette.
1970 LS-5 is 390 hp (gross) & 500 ft lbs of torque. Comp ratio is 10.25 to 1. Net hp is unpublished.
1971 LS-5 is 365 hp (gross) & 475 ft lbs of torque. Comp ratio is 8.5 to 1. Net hp is 285.
1972 LS-5 is 350 hp (gross) & 475 ft lbs of torque. Comp ratio is 8.5 to 1. Net hp is 270.
1970 engine uses TCS and re-calibrated distributor for emissions.
1971 engine uses CEC and re-calibrated distributor, for emissions.
1972 engine uses TCS and re-calibrated carburetor, distributor and A.I.R. emissions system. Timing specs are different from 1971.
Drifting
Joined: Jun 2003
Posts: 1,455
Likes: 5
From: Upstate South Carolina
We need to correct some mis-information that has been stated above by previous posters.
Yes, there definitely is a difference between the three years that the LS-5 engine was offered as an option on the Corvette.
1970 LS-5 is 390 hp (gross) & 500 ft lbs of torque. Comp ratio is 10.25 to 1. Net hp is unpublished.
1971 LS-5 is 365 hp (gross) & 475 ft lbs of torque. Comp ratio is 8.5 to 1. Net hp is 285.
1972 LS-5 is 350 hp (gross) & 475 ft lbs of torque. Comp ratio is 8.5 to 1. Net hp is 270.
1970 engine uses TCS and re-calibrated distributor for emissions.
1971 engine uses CEC and re-calibrated distributor, for emissions.
1972 engine uses TCS and re-calibrated carburetor, distributor and A.I.R. emissions system. Timing specs are different from 1971.
Yes, there definitely is a difference between the three years that the LS-5 engine was offered as an option on the Corvette.
1970 LS-5 is 390 hp (gross) & 500 ft lbs of torque. Comp ratio is 10.25 to 1. Net hp is unpublished.
1971 LS-5 is 365 hp (gross) & 475 ft lbs of torque. Comp ratio is 8.5 to 1. Net hp is 285.
1972 LS-5 is 350 hp (gross) & 475 ft lbs of torque. Comp ratio is 8.5 to 1. Net hp is 270.
1970 engine uses TCS and re-calibrated distributor for emissions.
1971 engine uses CEC and re-calibrated distributor, for emissions.
1972 engine uses TCS and re-calibrated carburetor, distributor and A.I.R. emissions system. Timing specs are different from 1971.
Actual horsepower went down each year for all engines between 70 and 72:71 LT-1 275 net (330 gross)
72 LT-1 255 net
71 base 210 net (270 gross)
72 base 200 net
Melting Slicks
Joined: Nov 2003
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From: St. Charles Mo
CI 5 & 8 Veteran
Mark, what changed from 71 to 72 on the LT-1's that resulted in a 20 hp loss? I can't think of anything except the T.I ignition or possibly timing and that doesn't count in my way of thinking.
