LT4 True LT4 HP

[soggytaco]

Maybe someone can help me? I have read that the 340 HP the LT 4 is rated at is just a min. and that most LT4s have much more HP. Most fall in the 350 to 375 range. Is this true and if it is what accounts for such a big HP range in similar power engines

 

[Edmond]

There used to be a member here that was with an independent shop that actually tested a number of stock LT4's. The range very even wider than what you thought. I want to say his name was Stan something while his co-worker, I think, was David Fulcher. It's been a couple of years. But anyway, they dyno'd LT4's and the range was usually from the 330 to 350 range but a few even deviated as far as 390.

 

[D.Rose]

http://www.corvetteactioncenter.com/specs/c4/1996/96perf.html

 

[Edmond]

http://www.corvetteactioncenter.com/specs/c4/1996/96perf.html

Yeah, that's the article. I also seem to recall reading that Stan did an article that was somewhat indept about the LT4 being underrated.

 

[B17Crew]

That’s a great write up, I don’t understand why Road & Track and Car & Driver 1/4 mile times are so poor. They both did the 1/4 in 13.7. LT4’s handily run low 13s.

My best run to date is 13.2 @ 107. Launched at around 1,200 rpm with stock Goodyear GSCs, 30 psi at all four corners, a full 20 gallon tank of Sunoco 94 and a bit of wheelspin off the line. Track elevation is approx 820 or 890 ft. above sea level, can’t remember exactly. I have a K&N air filter, doubt that that contributes much if anything.

I’ve never had mine dynoed but I expect it to be in the high 290 or 300 rwhp range.

B17Crew

 

[Vettelt193]

That’s a great write up, I don’t understand why Road & Track and Car & Driver 1/4 mile times are so poor. They both did the 1/4 in 13.7. LT4’s handily run low 13s.

My best run to date is 13.2 @ 107. Launched at around 1,200 rpm with stock Goodyear GSCs, 30 psi at all four corners, a full 20 gallon tank of Sunoco 94 and a bit of wheelspin off the line. Track elevation is approx 820 or 890 ft. above sea level, can’t remember exactly. I have a K&N air filter, doubt that that contributes much if anything.

I’ve never had mine dynoed but I expect it to be in the high 290 or 300 rwhp range.

B17Crew

I've heard rumors that chevy gave the car mags de-tuned LT4's for testing... so they wouldn't show off the extra power.

The main reason for this is the development cost of the LT4 was very low, versus the millions spent on the LT5 and LS1. Imagine how much cheaper the C5 would have been if it was LT4 powered...

 

[B17Crew]

I've heard rumors that chevy gave the car mags de-tuned LT4's for testing... so they wouldn't show off the extra power.

The main reason for this is the development cost of the LT4 was very low, versus the millions spent on the LT5 and LS1. Imagine how much cheaper the C5 would have been if it was LT4 powered...

Hopefully this underground rating of the LT4 will be a desired novelty down the road. Maybe it will help with value retention in 10 to 15 years. I plan on keeping mine for a long time. I love this car!

B17Crew

 

[Vettelt193]

Hopefully this underground rating of the LT4 will be a desired novelty down the road. Maybe it will help with value retention in 10 to 15 years. I plan on keeping mine for a long time. I love this car!

B17Crew

Yeah, unlike some other engine options that were limited in number the LT4 is desirable...

It also should be pretty easy to get parts for the long haul because the Gen II small block didn't change that much from the Gen 1 so most parts work in both.

 

[jcs44]

I've looked at most of the articles and research on this topic, and it appears that most stock LT4's will dyno at 290-300 at the rear wheels which works back to around 345-355hp at the crank.

 

[code5coupe]

Last year, a friend and I dyno'd our Corvettes on the same morning, the same dyno. His was a stock LS1, manual trans....rated by GM at 345hp.

His rwhp was 316
Mine was 311.

If the LT4 is underated, then the LS1 is also underated.
Personally, I think this 350 - 390hp LT4 thing is a bunch of baloney.

But, if it makes someone feel better to say "It's rated at 330 but really makes 380." then what's the harm?

Larry

 

[JEFNLSA]

Last year, a friend and I dyno'd our Corvettes on the same morning, the same dyno. His was a stock LS1, manual trans....rated by GM at 345hp.

His rwhp was 316
Mine was 311.

If the LT4 is underated, then the LS1 is also underated.
Personally, I think this 350 - 390hp LT4 thing is a bunch of baloney.

But, if it makes someone feel better to say "It's rated at 330 but really makes 380." then what's the harm?

Larry

Welcome Larry. I enjoy your posts on the CF. You are well informed and will be an asset to the CAC. Good to have you aboard.

Jeff

 

[Paul G]

I had my LT4 on the Dyno last summer. We turned out 311 RWHP. Allowing for 18% losses that calculates out to about 380 HP at the crank. Last summer our club, the Crown Point Corvette Club had track day down in Morocco Indiana. I ran against two C5 corvettes. I won both those races. I did get beat by a Z06. He ran a 12.80 to my 13.10. It would have been even closer if didnt spin so much in second gear. We are all just regular guys, none of us are drag race pro's. So it doesnt sound to me like the LS1 walks over the LT4 at all!

[FONT=&quot]BTW I took home the trophy in my class[/FONT]

 

[B17Crew]

I ran against two C5 corvettes. I won both those races. I did get beat by a Z06. He ran a 12.80 to my 13.10.
[FONT=&quot]BTW I took home the trophy in my class[/FONT]

13.10, that’s great! You have me beat by 1 tenth on my best time, I often thought if I could make it to the track more and become consistent, my LT4 would run a 13.1. Now I’m inspired.

What was your trap speed?

B17Crew

 

[Paul G]

13.10, that’s great! You have me beat by 1 tenth on my best time, I often thought if I could make it to the track more and become consistent, my LT4 would run a 13.1. Now I’m inspired.

What was your trap speed?

B17Crew

My trap speed was 106.13 on that run. I am hoping with a better launch and tweeking tire pressure a little maybe we can get in the 12's.

 

[B17Crew]

My trap speed was 106.13 on that run. I am hoping with a better launch and tweeking tire pressure a little maybe we can get in the 12's.

This is great, there’s a consistency with our times and trap speed. They’re so close... it’s good to see another LT4’s times in the same ballpark.

I have yet to adjust tire pressure, I run 30 psi in all four tires.

B17Crew

 

[code5coupe]

Allowing for 18% losses that calculates out to about...

Methinks your 18% is a little high. I can't see where drivetrain losses with a manual gearbox would be more than 15%...and probably a bunch less than that.
I put the crank output of a stock LT4 at 330-340. Just like the factory said.

 

[Greg@NASA]

Well, the Dynojet folks calculated 18% loss, whereas I'd always heard 15%, so I contacted 3 other Dyno operaters, and they ALL said 18% is accurate....there is a lot of drivetrain in an LT-4.

Just my $0.02

 

[jack volkert]

My 96 GS CPE. dynoed out at 307 RWHP totally stock. IMHO, the 330 HP is under rated by at least 20HP.

my .02

Jack

 

[Louis Bartay]

I've heard rumors that chevy gave the car mags de-tuned LT4's for testing... so they wouldn't show off the extra power.

The main reason for this is the development cost of the LT4 was very low, versus the millions spent on the LT5 and LS1. Imagine how much cheaper the C5 would have been if it was LT4 powered...

I have the three magazines from 1996 (somewhere) and if I remember correctly one mag had a 96 LT4 turn 13.33@108MPH the other two were 13.70@105 or so and the reason for the difference was that the slower 1/4 mile times were because the testers did NOT power Shift that was stated in the article (lift the throttle when changing gears and that is REALLY hard on a ZF) With 3:45 rear gears two of the mag's saw a top speed of 168MPH and the third mag did not test top speed they just printed estimated top speed .

 

[B17Crew]

With 3:45 rear gears two of the mag's saw a top speed of 168MPH

168 is moving! Fastest I’ve ever gone was 136... then I got a little nervous. There was still plenty left in the throttle though. It’s just nice to know that the power is there.

B17Crew