C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Why ?

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Old May 20, 2009 | 11:14 AM
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Default Why ?

What is it about the engine in the link below, that enables it to put out about 100 HP more than the 1996 LT4 corvette engine ?

http://www.crateenginedepot.com/prod...Product_ID=764

Stroke and cam is all I can see.

Last edited by ChrisWhewell; May 20, 2009 at 11:16 AM.
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Old May 20, 2009 | 11:47 AM
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In addition to the cam and stroke (which I did not look at closely...), I am betting that the testing method was different. For the LT4 in the '96, that is measured with all of the accessories attached and being driven. For the crate motor, that is probably just a bare engine on a dyno.
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Old May 20, 2009 | 12:32 PM
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The heads are GM's Fast Burns, which flow relatively well. One site shows them at 254 cfm; another site has them at 266 cfm.

The cam is 222/230 @ .050 with .543/.563 with 1.6s, so it's right around 3+ sizes up from the stock LT4 cam and even more duration and lift than the HotCam.

I couldn't verify the CR since there isn't enough info posted. I'd say, with those parts, the advertised numbers should be on target.

Jake

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Old May 20, 2009 | 12:35 PM
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Originally Posted by JAKE
The heads are GM's Fast Burns, which flow relatively well. One site shows them at 254 cfm; another site has them at 266 cfm.

The cam is 222/230 @ .050 with .543/.563 with 1.6s, so it's right around 3+ sizes up from the stock LT4 cam and even more duration and lift than the HotCam.

I couldn't verify the CR since there isn't enough info posted. I'd say, with those parts, the advertised numbers should be on target.

Jake

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thanks. I think it says CR = 9.7:1 and if you look up the part number given for the rockers, they're 1.5:1

edit: @ 6000 rpm, 76 cfm is the max a single cylinder on a 350 can use at 100% VE.

Last edited by ChrisWhewell; May 20, 2009 at 12:51 PM.
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Old May 20, 2009 | 10:28 PM
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On a dyno with no accessories, more cubes, and bigger cam.

LT4 is 330 with accessories.
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Old May 20, 2009 | 10:56 PM
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Originally Posted by James93LT1
On a dyno with no accessories, more cubes, and bigger cam.

LT4 is 330 with accessories.
that would be my guess.
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Old May 20, 2009 | 11:13 PM
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Default 425 hp LT4 with HOT CAM

in regards to comparing a GM 383 crate engine rated at 450 hp with an
LT series engine, please be advised that YEAR ONE markets an LT1 upgrade kit referred to as the "LT4 Conversion Kit" which includes an
LT4 "HOT CAM"; this combination is rated at (no surprise) 425 hp;
see http://www.yearone.com/pco/G_0907/full.asp?page=76
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Old May 21, 2009 | 08:52 AM
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This is how a crate LT4 was rated

http://www.s-series.org/htm/tech/GMP...ts/014-019.pdf
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Old May 21, 2009 | 11:06 AM
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Originally Posted by James93LT1
thank you. Popping an 846 cam in there would probably add some more power, but how much is anyone's guess. Then, going with a longer stroke, even more. A 383 w/LT4 heads and manifold ran at 10..8:1 compression with reverse cooling could probably get over 450HP

It seems that LT4 was the ultimate refinement of the sbc.
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Old May 21, 2009 | 11:43 AM
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I would doubt the LT4 being the ultimate SBC to be honest. And the loss from accessories is really minmal the water pump has to be used in both cases, power steering minimal unless you are truning the steering wheel same for altenator unless it is charging the battery... Look at the size of the drive belt then make your decisions about losses..
Dave
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