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Old 08-24-2003, 11:53 PM
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1970 lt1 350?

i hear that the 1970 lt1 350 has 370 hp stock! can any1 tell me how true this may be?this is the motor im tryin to build!! t/y

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Old 08-25-2003, 01:54 AM
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it did have 370 "gross" horsepower. Gross means measured at the flywheel, with the best timing and fuel curve, no transmission or driveshaft power loss, no power steering pump or alternator to drag away more power. the "net" figures are measured with the engine the car with all accessories, thus the power level will be somewhat less. in 1970, the factory performance wars were still going on, only to be smoldering ruins within the next 2 years, the EPA stepped in, high compression, dual quads, dual exhaust, aluminum high rise intakes, solid lifter cams, all vanished. to build this same engine today on the street would be the same as driving a time bomb, low octane gas on 11:1 compression spells detonation, which spells engine failure, on catastrophy levels.
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Old 08-25-2003, 05:47 AM
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DoubleVision is correct, these late 60's and early 70's engines were pretty much peaked for street use. Solid lifter cams, 11 to 1 forged pistons and a host of other neat severe duty GM parts. The factory rated HP figures were actually under rated, due to insurance constraints. The famed 302 Chevy of Z/28 lineage was very conservatively rated at 290hp. It's hp rating was actually closer to 400.

Vince
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Old 08-25-2003, 01:54 PM
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Actually for comparison reasons I think Gross Hp is better to compare engines.Being as most crate motors are gross hp rated.And most Hotrod mag builds are gross hp.
Basically that Lt1 motor has 40 more horse than the standard 350 vortec crate motor.So your still comparing and in the same car both would have the same acesories and tranny,exhuast etc...so to me gross hp is better for compareing Engine #s.
Either way should run like a raped ape.But bring a jug of race fuel to mix in at fill ups.
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Old 08-25-2003, 05:02 PM
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it could be a 285hp lt1... not all lt1's were the same, sure they had the same basic head desighn but there was a lower compression version with a smaller camshaft and stuff too... but even a 285hp lt1 makes for a good enigne...
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Old 08-25-2003, 05:07 PM
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The LT1 of the early seventies, 70, 71, 72 were all the same HP.

Vince
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Old 08-25-2003, 07:27 PM
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Hi guys,all these old motors are real popular, I would rather say "i have a 302 chevy or a 427 or the like.
I was wondering if anyone can post a link to specific engine specs,say to build a 383 stroker or the like.the best heads, the right size rods,rockers, etc.to give you the desired h.p. i dont want to buy fancy aftermarket heads,I want the casting #s for the goodies, and exactly what to do , 3 angle valve job?what size? how much to cut out to match the ports .cam lift duration.... something lets say .......Tried - Tested - and - True.... thanks guys mike
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Old 08-25-2003, 07:41 PM
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Hey Vince,
When you say that 70, 71, and 72 LT-1's had the same HP, what do you mean? In 72 they are SAE Net figures. Also in 71 and 72 the compression dropped from 11 to 9. The 70 model is listed as 370, the 71 is listed as 330, and the 72 is listed as 255.
Obviously a Z-28 fan, do you have John Hoopers book on Camaros?
Vern
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Old 08-25-2003, 07:54 PM
E.T. divided by $ spent= Speed
 
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mikeweyman,look up "ryan's car page" on google this guy has over 120 differant SBC engine combos in charts on his site.I'm sure you'll find what ya want there.
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Old 08-25-2003, 09:03 PM
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The LT1's of the early seventies (70, 71, 72) were in the Z/28 Camaro and certain Corvettes. They all still had 11 to 1 compression, no LT1 of that time period ever had 9 to 1 compression. That was when Z/28 meant performance.

Vince
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Old 08-25-2003, 10:28 PM
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The 1970 LT-1's were rated 360HP in Camaros & 370HP in Corvettes. All GM production cars got reduced compression in 1971, with the LT-1's rated at 330HP with 9:1 CR. There were no 11:1 production cars after 1970.
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Old 08-26-2003, 10:00 AM
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1970 LT1=very good motor!

My buddy had a '66 Chevy II 4-speed. He put a 11:1 LT1 crate short block in it. He used the Phase 1 Bowtie heads and the second design (offroad) LT1 cam from GM with the GM recommended valve train parts. He also used a Torker 2 intake with a Holley 780 VS. That motor would scream. The second design cam pulled up to about 7500 RPM and you could feel it too. This motor came stock with a very good bottom end also with a forged crank, forged pink rods, and forged pistons. Even though the new Z's run very strong without having to turn a lot of RPM, it was something special to go by someone, shifting into third at about 7200 RPM with duals dumping into twin cherry bombs.
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Old 08-26-2003, 10:30 AM
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I respectfully disagree jimfulco, I have a Chevrolet performance book from that era and it details a 71 Z/28 Camaro with a 375hp LT1 in it.

Vince
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Old 08-26-2003, 01:44 PM
E.T. divided by $ spent= Speed
 
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I kinna thought compression dropped to 9:1 in 1971 too.But maybe I'm wrong.
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Old 08-26-2003, 06:19 PM
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According to everything I have seen...

70 LT1 Z28 is 360 hp

1971 LT1 Z28 is 330hp with 9.0:1


Lots of books have misprints and these figures may not be correct anyways as was stated before. Could be underrated or overrated.

The only number I ever worry about is, the one at the end of the 1/4. Like the old saying goes, you can have 500 horse, but if you can't put it to the ground, what good is it.
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