1970 vs 1971 LT1 Engine
Heel & Toe
Joined: Jun 2003
Posts: 19
Likes: 2
From: Sharpsburg GA
Re: 1970 vs 1971 LT1 Engine (jims427)
I'm not an expert on these engines, but from what I recall from 15 years ago the major differences were the compression (as you mentioned) and the fact that they went from a solid lifter cam to a hydraulic grind. These two are the major reduction in H.P. rating. I believe the block, heads, and induction are basically the same. Hope this is accurate and helps.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Re: 1970 vs 1971 LT1 Engine (MI81)
Just compression ratio. They had solid lifters from 70-72. The head casting numbers are different and the chamber size is different. The block, crank, rods, cam, and most everything else was the same. The 72 went down to 255 HP but that was from gross to net HP. Basically the same engine from 70-72 except compression ratio.
Melting Slicks
Joined: Mar 2002
Posts: 3,252
Likes: 6
From: The Colony Tx
Re: 1970 vs 1971 LT1 Engine (jims427)
On the engine itself, I am pretty certain it was only compression. The reason AIR was added in 72, was that they moved the red line down so folks wouldn't throw the belt for the A/C.
Heel & Toe
Joined: Jun 2003
Posts: 19
Likes: 2
From: Sharpsburg GA
Re: 1970 vs 1971 LT1 Engine (jims427)
gordonm - Your right, my mistake. i should have researched this before I blurted out the answer - I did find a link that may be helpfull in other questions. http://www.hotrod.com/thehistoryof/62079/index1.html
:bb
:bb
Melting Slicks
Joined: May 2001
Posts: 2,131
Likes: 4
From: May help you? You can sure as hell try!
Re: 1970 vs 1971 LT1 Engine (jims427)
The '71 and '72 had hardened valve seats and lower compression to prepare for the phasing out of leaded fuel. Because of the 11:1 compression, the '70 still required leaded fuel. The '72 was rated at 255HP because the industry moved to the new SAE standard for net horsepower ratings which is less "optimistic" than the earlier gross ratings. Other than that, there is no difference between the '71 and '72 LT-1 other than a sticker on the air cleaner (literally).
Safety Car
Joined: Feb 1999
Posts: 3,631
Likes: 14
From: Fountain Hills AZ
Re: 1970 vs 1971 LT1 Engine (LemansBlue68)
In 1971 GM published both net and gross figures. The `71 Corvette LT-1 was 330 hp gross, 275 hp net. Net ratings for the other engines were also higher in `71 than in `72.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Safety Car
Joined: Apr 2001
Posts: 3,581
Likes: 28
From: Spring, Texas
Re: 1970 vs 1971 LT1 Engine (Gordonm)
Just compression ratio. They had solid lifters from 70-72. The head casting numbers are different and the chamber size is different. The block, crank, rods, cam, and most everything else was the same. The 72 went down to 255 HP but that was from gross to net HP. Basically the same engine from 70-72 except compression ratio.
Drifting
Joined: Jun 2003
Posts: 1,455
Likes: 5
From: Upstate South Carolina
Re: 1970 vs 1971 LT1 Engine (SharkAttack)
LT-1 engines from 70 to 72 were mostly the same, but horsepower, both gross and net, did drop each year as happened to all corvette engines until 1975 when the L-82 had 205hp. :cry Biggest difference in the LT-1's was the compression, but vacuum advance, ignition timing, and other stuff changed each year also leading to the drop in hp.
