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1970 vs 1971 LT1 Engine

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Old 11-17-2003, 05:30 PM   #1
jims427
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Default 1970 vs 1971 LT1 Engine

Other than the compression ratio what were the differences between the 1970 and 1971 LT1 Engine? If I remember the listed hp was 370 vs 330.
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Old 11-17-2003, 06:36 PM   #2
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Default 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.
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Old 11-17-2003, 06:54 PM   #3
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Default 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.
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Old 11-17-2003, 07:22 PM   #4
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Default 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.
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Old 11-17-2003, 07:26 PM   #5
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Default 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
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Old 11-17-2003, 07:38 PM   #6
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Default Re: 1970 vs 1971 LT1 Engine (MI81)

On the street it means nothing. The one in good repair will blow the doors off the other
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Old 11-18-2003, 01:18 PM   #7
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Default 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).
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Old 11-18-2003, 07:47 PM   #8
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Default 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.
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Old 11-18-2003, 10:02 PM   #9
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Default Re: 1970 vs 1971 LT1 Engine (Gordonm)

Quote:
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.
:iagree:
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Old 11-19-2003, 01:10 AM   #10
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Default 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.
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