LT4 LT4 "real" HP

[jcs44]

I know that we all believe that the LT4 motor was underrated at 330 hp. I would like to hear from any of you who have had a dyno test done on a stock LT4. I read of one a couple of days ago that tested at 365hp at the crank and this was claimed to be pretty typical.

Thanks, John

LT4 Vert, blk/blk

 

[Skant]

From my research, it looks like 360hp or so is the most typical. It is claimed that there was wide variation in stock horse power on the LT4. Ranging from 330hp to nearly 400hp. But the extreme ends of that range were rare.

- Skant

 

[nearmiss]

As a relatively new owner of an LT4, I'm pretty surprised that there should be this wide variation in stock HP. I don't doubt that its true, but doesn't it kindof imply a lack of manufacturing quality control? Either that or there is a really wide range of state of tune out there. Any body got a good explanation why this variation exists?

- nearmiss

 

[6 Shooter]

LT4 HP - This 1's had a few lengthy discussions . . .

The performance figures and specifications listed below were compiled by Forum Member, Stan A (Stan Adelman) of Auto Performance Test Lab located in Atlanta, Georgia. The Corvette Action Center would like to thank Stan for allowing us to post his Performance Review Data here.
Regarding the stock LT4 horsepower numbers, Stan explains:

The LT4 really can vary in Horsepower and torque. Like I said, the average one on the street comes in between 350hp to 360hp. We have tested over 125 LT4 units since 1996 and found that less than 25% of the units come in under 345hp. About 15% come in between 360hp and 375hp. About 10% range between 375hp and 385hp. 2% have been found to hit the very low 390hp range. This is all stock from Bowling Green. Keep in mind that the torque also increases too. One unit came in on the dyno at 392hp/426lbs-ft torque @5850rpm. Very rare but still present out there. This is why there have been reports of LT4s running with or past ZR1-LT5 cars over the years. Basically, the LT4 will out run the LS1 in 75% of all cases.​

​

Here's the link . . .

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

Later . . . . . .
6 Shooter

 

[Gary04Z06]

Mine dyno'ed with 298rwhp a few months ago. Only mods were, K&N filter, muffler elims, and hypertech programmer (turn fans on earlier) 160deg t-stat.

 

[UB2 SLOW]

I saw a stock one dyno at 301 rwhp about a year ago. That comes out to about 354 hp.

 

[Vettelt193]

As a relatively new owner of an LT4, I'm pretty surprised that there should be this wide variation in stock HP. I don't doubt that its true, but doesn't it kindof imply a lack of manufacturing quality control? Either that or there is a really wide range of state of tune out there. Any body got a good explanation why this variation exists?

- nearmiss

GM has a 5% quality control standard on engine power (so figure +2.5% and -2.5%).... They purposely under-rated the LT4 (to protect the ZR1 owners, and to make sure they didn't look stupid spending millions on the LS1 platform). so figure it should have been rated at 345-350 HP... with this in mind, The normal high end would be in the 360 range, the normal low end would be 340 range.... GM also has a good track record when it comes to giving you the HP that they advertise... meaning, if GM says you are getting 350 HP, you usually get 350+ HP, not 'close to' 350 HP (this is how ford does business... their track record is to advertise a power output, then get within the range plus or minus)

 

[wx briefer]

I have yet to see any significant variation in HP with stock LT4. I have compared 4 with dyno pulls and there is no more than 2 or 3 HP difference. For me to believe the stories of wide variation, I would have to see it for myself. Stock will yield right at 300 RWHP (SAE corrected on a dynojet chassis dyno). If one opens up the intake, installs HOT cam, headers, and hi flow cats w/ good aftermarket exhaust, you can expect 340 RWHP with stock programming. Throw a little LT1 editing in there and one can get another 15 to 20 HP. If anyone has a difference of opinion, please back it up with a dyno pull sheet.

 

[jcs44]

I have yet to see any significant variation in HP with stock LT4. I have compared 4 with dyno pulls and there is no more than 2 or 3 HP difference. For me to believe the stories of wide variation, I would have to see it for myself. Stock will yield right at 300 RWHP (SAE corrected on a dynojet chassis dyno). If one opens up the intake, installs HOT cam, headers, and hi flow cats w/ good aftermarket exhaust, you can expect 340 RWHP with stock programming. Throw a little LT1 editing in there and one can get another 15 to 20 HP. If anyone has a difference of opinion, please back it up with a dyno pull sheet.

Thanks. This would appear to track with what several others have stated as well. 300RWHP equates to about 353 HP at the crank, right? And, +/- 2% would make the probable range in the neighborhood of 345-360.

 

[boulderlt4]

I have a 96 LT4 with almost 25K miles. It has a K&N air filter, other than that...bone stock.

I just took it down to the dyno to get some baseline numbers, as I am about to do some work on it.

It ran 294.6rwhp (@ 5750 rpm), with 315rwt. Top run was 307.2 rwhp, with 327 rwt.

Explains why I haven't lost to a LS1 yet!!!

 

[sj20343]

boulderlt4,


What kind of work are you about to do to your LT4? I am a fairly new owner of an LT4 myself, and would like to do some work on mine as well. Not being an expert, I'm not sure what to do to increase performance.

 

[kblack_LT4]

My Dyno results

I'm looking at my dyno sheets right now done at LD Motorsports May 22, 2004. It has an x-pipe, K&N open filter, and corsa mufflers. The three dyno pulls were:

HP Torque
302.5 309.7
300.4 305.3
303.4 309.2

I agree, these are in the normal range. I wish I had some of the higher torque ratings some had. I am planning on a few mods but I want to get some baseline times in first. Maybe its because of some past cars I've had, but this car doesn't pull as hard as them, or feel as strong (and it isn't). I am hoping that with the mods it will have that Z06 type pull I'm looking for.

Ken

 

[stgry1]

. It has an x-pipe, K&N open filter, and corsa mufflers.

Hey Ken, were did u get your x-pipe??

 

[Gary04Z06]

Hey Ken, were did u get your x-pipe??

Dave at R-D racing has one he was going to use on his race car for sale.
It's a Dr. Gas 2.5" x-pipe for $100, if anyone is interested.
Call him at: Dave Cooper
R-D Racing Enterprises, Inc
573-756-6954 Office
573-756-6372 Fab Shop
dcooper@r-dracing.com


Tell him Gary says hi........

 

[kblack_LT4]

The x-pipe purchase

Hey Ken, were did u get your x-pipe??

\

Sorry to be so late but I've been out of town. I got it off ebay, they are on there a lot. Do a search for x-pipe, there are magno flows in different diameters for about what I paid for mine ($57), lots cheaper than retail! Best of luck.

My home email is kblack@geusnet.com

Ken

 

[NC-LT4]

Where is the x pipe located? Before/ after the resonator? Or does it replace the resonator?
Thanks for the info.

 

[kblack_LT4]

LT4 HP & X-pipe

Where is the x pipe located? Before/ after the resonator? Or does it replace the resonator?
Thanks for the info.

I removed my resonator and installed in place of it. This required that the muffler shop add a short section of pipe to it to make up the leangth but it wasn't much. They used clamps that were installed sideways up front and welded it in the rear as the clearance was to tight for clamps there. So it removes the resonator (in my case it is what I wanted) and replaces it. My lift gets installed this week in my shop, if you email me, next week I can take some pictures and send them if you'd like.

Hope this helps.

Ken Home email is kblack@geusent.com

 

[Shriker]

I have seen several stock LT4's dyno and have seen many dyno sheets posted on boards like this and others. The VAST majority of LT4's dyno between 290 and 300 rwhp stock. I have heard of some being way strong and have seen the section of this site claiming that but from what I have seen, read and experienced (which is alot of real world cars), they were almost all within that ten rwhp range.

Mine made 293 rwhp and 305 lb/ft stock. With cut lid , EM longtubes, B&B Xpipe and catback it made 317 rwhp and 327 rwt. Now with the addition of worked heads, Hot Cam, 1.7 rr's, ported intake, 52mm TB , Mezeire electric water pump and custom tune it has made 380 rwhp 350rwt with 4.10 gears (which show 5-7 less than stock gears on the dyno)......still very streetable

 

[cgtarga1]

re:LT4 mods

I have yet to see any significant variation in HP with stock LT4. I have compared 4 with dyno pulls and there is no more than 2 or 3 HP difference. For me to believe the stories of wide variation, I would have to see it for myself. Stock will yield right at 300 RWHP (SAE corrected on a dynojet chassis dyno). If one opens up the intake, installs HOT cam, headers, and hi flow cats w/ good aftermarket exhaust, you can expect 340 RWHP with stock programming. Throw a little LT1 editing in there and one can get another 15 to 20 HP. If anyone has a difference of opinion, please back it up with a dyno pull sheet.

I too have an LT4 with corsas, and a hot cam. I only have 314 hp. What do you mean by 'opens up the intake'? Do you feel the headers or hi=flow cats should be next? thanks

 

[lt46spd]

Horsepower

Just had my stock LT4 except for K&N air filter dyno at 360hp. Added a Borla cat back exhaust and new dyno hp at 380. No brag just fact.