LT4 horsepower
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4th Gear
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LT4 horsepower
I have read that GM under rated the LT4 at 330 hp, and that the correct number is closer to 350-360 crank hp on a stock motor. Is this true?
The Grand Sport Registry has dyno runs from unmodified cars that peak at over 300 rwh.
The Grand Sport Registry has dyno runs from unmodified cars that peak at over 300 rwh.
Le Mans Master
Joined: Oct 2004
Posts: 6,314
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From: South-central Missouri
Supporting data...sota...
Originally Posted by black96lt4
I have read that GM under rated the LT4 at 330 hp, and that the correct number is closer to 350-360 crank hp on a stock motor. Is this true?
(in effect) Dyno tests of 125 LT4s resulted in the following stats (credited to by Stan Adelman of Auto Performance Test Lab in Atlanta, GA.):
Less than 25% of (LT4s) dynoed <345hp,
about 15% fell into the 360 to 375hp range,
about 10% between 375 and 385hp,
2% hit low 390s hp
If I do the math, that means 48% must be in the gap between 345 and 360 hp (the article said average is between 350 and 360hp)
I'm told that every dyno is different, so getting an absolute reading comparision is difficult between machines. But, relative comparisions on the same machine are accurate to a much greater degree. A grain of salt is possibly in order here as well.
Hope this helps.
P.
Race Director
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From: St. Peters MO Sometimes you have to prove yourself by doing alot of killing or alot of dying...
Wasn't it determined a while back that the LT1 was also under rated in the vettes, but not the F-bodies??? I may be wrong on this... it was posted in a thread a while back and I am at work so I don't have time to do a search...
Race Director
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From: Everyday you must choose between the pain of discipline and the pain of regret. Fredericktown, OH
Mine made 305 with Magnaflows and a cold air kit. I don't believe the cold air kit makes any difference sitting still and I doubt the mufflers made much difference either.
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From: Go Dawgs!
YES Its True
bone stock to the air filter and mufflers i pulled 306.1 RWHP / 308.2 RWTQ.....
and it was a hot day and a hot engine
thats 360 CHP and 363 CTQ
Now after welding straight pipes in the place of mufflers and resonator, and a cut airlid- still stock filter, i think i should be in the 316RWHP range which is 372 CHP
Long tubes and high flows should buy me 12-18 RWHP
a LT4hot cam with 1.7RR's should buy me 20-30 RWHP
a DYNO tune should buy me another 10-20 RWHP
so in the end i will be looking in the worst case 360RWHP and best best case 385 RWHP
--Kevin
bone stock to the air filter and mufflers i pulled 306.1 RWHP / 308.2 RWTQ.....
and it was a hot day and a hot engine
thats 360 CHP and 363 CTQ
Now after welding straight pipes in the place of mufflers and resonator, and a cut airlid- still stock filter, i think i should be in the 316RWHP range which is 372 CHP
Long tubes and high flows should buy me 12-18 RWHP
a LT4hot cam with 1.7RR's should buy me 20-30 RWHP
a DYNO tune should buy me another 10-20 RWHP
so in the end i will be looking in the worst case 360RWHP and best best case 385 RWHP
--Kevin
Last edited by A BirdMan Converted; Oct 7, 2005 at 03:40 PM.
Le Mans Master
Joined: Oct 2004
Posts: 6,314
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From: South-central Missouri
"Boulder" as in Colorado???
Originally Posted by boulderlt4
Bone stock mine dynoed 298 rwhp on a mustang dyno.
P.
Safety Car
Joined: Jun 2004
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From: lafayette co
Originally Posted by Paul Workman
I'm guessing you live in Boulder CO? And, if so, was the dyno reading you got on the LT4 also done near the "Mile High City"??? I'm thinking if that is true, then it might have benefitted from a lower elevation run. I lived in Bailey Colorado for 4 years and I know how sluggish my cars were up there compared to here in middle IL.
P.
P.
Car was a lot faster when I lived in Cali. Had to mod the crap out of it when I moved it here, because it felt like a different car.
Le Mans Master
Joined: Oct 2004
Posts: 6,314
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From: South-central Missouri
Making a case for FI, I recon....
Originally Posted by boulderlt4
Those are altitude adjusted numbers.
Car was a lot faster when I lived in Cali. Had to mod the crap out of it when I moved it here, because it felt like a different car.
Car was a lot faster when I lived in Cali. Had to mod the crap out of it when I moved it here, because it felt like a different car.
I'm trying to figure out zakly whicha-way to go w/ my 450-475 hp goal for m LT1, keeping in mind I may be back in Colorado again, living at 8500+ feet. It would prolly take all of a 383, LT headers, and cam just to get back to where I am now at 600 ft AMSL w/ the LT1!
Much as I would rather avoid FI and associated complexities, a SC would offer an immediate hp lift, and I could do the lower end in a year or so. That might be a way to solve the thin air problem.
I'm not making a point...Just sorta thinking out loud, I guess!
P.
That thing must have been built on a wednesday
Instructor
Joined: Dec 2004
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From: Roselle IL
Originally Posted by black96lt4
I have read that GM under rated the LT4 at 330 hp, and that the correct number is closer to 350-360 crank hp on a stock motor. Is this true?
The Grand Sport Registry has dyno runs from unmodified cars that peak at over 300 rwh.
The Grand Sport Registry has dyno runs from unmodified cars that peak at over 300 rwh.
On my dyno, it stated "CF: SAE Smoothing" Is this different than what it states on other dyno sheets?
Thanks
Le Mans Master
Joined: Oct 2000
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From: St. louis, MO
Originally Posted by MetalVette
Lt-1's Rock though. Easier to upgrade. 
The LT-1s are great, but the LT-4s are basicly the same as the LT-1s, the LT-4 is simply already factory upgraded in some areas.