LT4 LT1 vs. LT4

[snow0925]

I recently read an article in Car and Driver (1996 issue) that stated the LT1 engine was the same (performance wise) as the LT4. Thay stated that 0-60 and quarter mile times were identical. The only difference was an increase in top speed of 7mph. Needles to say they were very disappointed. Has anyone driven both....are their findings correct or is there really a little more punch in the LT4. Please let me know because I'm considering buying a LT4...however if there is really no difference I'll get a LT1 and save a few bucks.
Many Thanks

 

[Vettelt193]

I have owned both... had a '93 LT1, and now a 96 LT4... The LT4 is WAY WAY BETTER! It has a ton of low end torque, not to mention the torque curve is almost flat... more power on top... everything is better... you can feel the power all over the power band...

-Rumor has it that the car mags were given cars with reduced power to test... this was to protect the C5's LS1 and the ZR1's LT5... the development cost of the LT4 was very low, and they spend millions on the LS1... also, just a year earlier the ZR1 option was around 30 grand... the LT4 was only around $1,500. Basically, chevy had to make it seem like LT4's only had 330 HP, when they really have much more, so they de-tuned LT4's for the magazines.

 

[Edmond]

You never can really trust what those magazine guys say anyways.:L

 

[secondchance]

When you have LT1 redlining @ 5700 and LT4 redlining at 6300, regardless of any magazine article, you will feel and see the diffrence. By the same token, LT5 redlining at 7200, you can certainly feel and measure the difference.
I vote for LT4.

 

[6 Shooter]

I recently read an article in Car and Driver (1996 issue) that stated the LT1 engine was the same (performance wise) as the LT4. Thay stated that 0-60 and quarter mile times were identical. The only difference was an increase in top speed of 7mph. Needles to say they were very disappointed. Has anyone driven both....are their findings correct or is there really a little more punch in the LT4. Please let me know because I'm considering buying a LT4...however if there is really no difference I'll get a LT1 and save a few bucks.
Many Thanks

I've owned both also, there is a Large Difference . . .

I wonder if they were comparing the LT4 to a stock LT1.

 

[secondchance]

By the way, I remember the particular article. Horse power is only a part of an equation in acceleration. LT1s were rated 340 lb-ft @ 4000 where as LT4s were rated 300 lb-ft @4500. What this implies is that LT1s are marginally stronger until higher rev where LT4 starts to show its horse power advantage. With 30 hp advantage and peak torque occuring higher in rpm, you will not see a clear advantage in e.t. But you probably will see slightly higher trap speed. True advantage is in the feel of the acceleration. LT4 probably shows its superiority at higher speed.

 

[Edmond]

Here is an article written by one of our guys, Stan A:

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

It's an excellent article; I've spoken to Stan a few times and he is a very knowledgeable man about automobiles.

 

[compyelc4]

My neighbor has a well-kept LT4. It has a few more miles on it than my '95 LT-1. I have not noticed a significant seat-of-the-pants feel leaving the line, but that little cuss does get me on the upper band........like you say. I'm running the 308 rear. Don't know what he has in his.

The LT-4 definitely looks classier, if you prefer blue over my Bignanner! His wheels.........now that's another story. I'm not sure I care for them. The strips.......those are cool!

 

[6 Shooter]

Don't know what . . .

I'm running the 308 rear. Don't know what he has in his.

3.45 (LT4)

http://corvetteactioncenter.com/specs/c4/1996/96overview.html

 

[Edmond]

I think with a few bolt ons, you'll be running neck and neck with C5's with no problem.

LT4 is definitely a great engine that I think will stand the test of time. Then again, would they put a crappy engine in a 'Vette?

 

[Vettelt193]

I think with a few bolt ons, you'll be running neck and neck with C5's with no problem.

Neck and neck? I kill C5's all the time... there are many reasons for this...

-Most C5's (like C4's) are automatic
-C5 has a higher drive train power loss
-LS1 usually has less HP and torque than LT4

I love seeing the look on C5 owners faces when I pass them by! Most of them have no clue what an LT4 is, and I think they just assume it is a ZR1 that just passed them!

note: ZO6's have, and will continue, to outrun my LT4

 

[77-4speed]

The following are the specs on the 97 C5

Engine Specifications
Type Overhead valve, pushrod V8, cast aluminum block and heads, 2 valves/cylinder
Bore 3.90 in.
Stroke 3.62 in.
Displacement 5.68 Liters
Compression Ratio 10.1:1
Horsepower 345 bhp @ 5600 rpm
Torque 350 lb-ft @ 4400 rpm
Redline (RPM) 6,000


How exactly is it that an LT4 could beat a C5 when the only advantage it has is the 300 rpm increase in redline? I guess an automatic could be rolled easily enough, but a stick?

How much power gets to the ground on an LT4? The C5's get about 300hp +/-. Also, the C5 is lighter.

Russ

 

[Vettelt193]

I have understood the C5 has a bigger power loss, about 18% for the 6 speed cars. That puts a '97 around 285 hp at the rear wheel. even less for the automatics.

 

[Gorgon]

From what I understand there were few differences between the LT1 and LT4 and I am thinking about adding these changes to my LT1. I believe, for the most part, that the changes were roller rockers, intake and exhaust?

 

[77-4speed]

An unmodded 97 C5 MN6 puts 295-305 hp to the ground, depending on atomospheric conditions. The drive train loss is only ~13-15%. I've seen quite a few dyno runs on stock C5's above 300hp at the wheels. Now the automatics do have an 18-20% power loss at the wheels.

Russ

 

[6 Shooter]

Differences between the LT1 & LT4 . . .

From what I understand there were few differences between the LT1 and LT4 and I am thinking about adding these changes to my LT1. I believe, for the most part, that the changes were roller rockers, intake and exhaust?

Here they r . . .

http://corvetteactioncenter.com/specs/c4/1996/lt1lt4.html

 

[Vettelt193]

The best link I think that is available is http://home.tir.com/~steveher/lt4.html

I have seen many people try and fail at turning LT1's into LT4's. (I have done this first hand)... There are so many differences between the two... Crankshaft, Camshaft, Pistons, timing chain, rockers intake manifold, injectors, valves... the list goes on and on!
-you cannot make an LT1 into an LT4 without a rebuild... it would be not be worth rebuilding an LT1 to LT4 specs, so not one person to my knowledge has had any success. If you have an LT1, treat it as such, and do modifications to it as an LT1... it is a waste of time trying to turn it into an LT4

 

[RubyDropTop]

Vettelt193 -

What are your feelings on putting the LT4 1.6 roller rockers in an LT1? That would be an alteration that I would think would be worthwhile. What do you think?

 

[Vettelt193]

I love roller rockers! A set of 1.5's gives a power increase the best way, through a reduction of friction... 1.6's are up to the person though... 1.6's will increase your peak hp RPM, so you will gain power, but it will be higher up in the power band... this means you will lose a bit on the bottom (this is where things get shady, since you are swapping to full rollers, the bottom end tends to remain unchanged, or get slightly higher, the top end has bigger increases... the only real way to test is with a set of full roller 1.5's Vs. full roller 1.6's, what should happen is the set of 1.5's will have more power on the bottom, 1.6's more on top)

-My favorite setup for LT1's is 1.6 on the intake, 1.5 on the exhaust.... first of all, some LT1's require new valve springs to go to 1.6 rockers... The only problem with the springs is on the exhaust side, so the mixed set eliminates the need for new springs. (nothing is worse than doing a job twice, because a spring is binding, AND finding a set of springs when the car is apart)
-The mixed set seems to be a happy medium for the LT1. You get better gas mileage, cooler engine from reduced friction, and more power spread fairly evenly accross the powerband.

PS there is a company that sells the mixed set already, I just can't rember, or find which one it is

 

[RubyDropTop]

You mention a problem with the springs on the exhaust side...what is the problem that you are referring to? :confused