Ok, I'm a new corvette owner (3 months). 1996 LT4 w/ 21k miles.
I've been reading and research performance parts.

The only SIGNIFICANT "bolt-on" performance I can find is an Electric water pump (+10-12rhp). It seems these cars are already designed very well.

Examples: Exhaust upgrade, maybe +3rhp (for $1000). SLP intake upgrade, maybe +3rhp (for $300). 58mm TB, no gain on stock. Injectors, no gain on stock. etc... etc... etc...

It seems (besides Opti under H20 pump) these cars are designed very well for performance....

Corvettes are awesome!! Lovin' it.....


(this doesn't speak of internal engine upgrades, which of course would be an upgrade to any engine)

 

Try the Hot Cam...it's bolt-on.
Or 4.10 gears.
Or an aluminum flywheel.

Any of those three will give you more seat-of-the-pants acceleration than an electric water pump will.

(Electric water pumps don't increase horsepower, they simply take a more labyrinthine route in their power requirements. The engine still has to supply additional power to run the alternator (which is powering the pump) instead of powering the pump directly. The only way an electric pump can free up hp is if it pumps less water than the stock pump.....ain't no free lunches)

Larry
code5coupe

 

Well said, Larry.

Although I don't have 'em, I think you'll find many people here will reply that the 4.10 gears will give you the biggest "kick in the pants" for the buck. There is a place local to me who will do 4.10s out the door for just a touch over $600. Then again, that's ALL they do, so I'm sure they're efficient in the process.

As for exhaust, I added a Corsa not for a power increase, but for the aesthetic improvement I felt it made over the stock tips and for the better sound at WOT.

When it comes right down to it, you've got to do what makes YOU happy and what you think is best for YOUR car, your wants, and your needs. The LT4 is plenty capable as-is - even for an 11 year old car - don't ignore the great gains to be made in suspension and brake upgrades!

 

IMHO long tube headers, electric waterpump, and possibaly 1.7 scorpian roller rockers with new springs (if you consider springs and rockers bolt on. ) Other then that, go 4.10 gears, cam and have the heads ported. You already have the larger valves. But you are right, the LT1-4 has a good exhaust and intake. Not much to be gained with either of these.

 

Best upgrades IMO are..
Ported Heads and Custom Cam (Not Cheap but 65-100hp gain with complementing mods)
Nitrous (Complete Setup about 2k for everything, up to 150hp on stock engine)
LT Headers (About $1100-1200, 15hp gain)
Supercharger (about $4000+, 100-125hp gain)

Other things
Gears (Lower ET's)
Sticky Tires (Better Traction, Lower ET's)
Bigger TB (Mostly to complement other mods)
Exhaust (Higher Gain on early C4's but will also complement other mods)
Custom PCM Tune (10+ gain and very necessary when doing bigger mods like heads and cam or Nitrous)
Electric WP (Those that have switched to the EWP have reported a 6-10hp gain and that eliminating the mechaincal pump has a gain high enough to offset the increased draw on the electrical system)
Pulleys (6-8hp)
1.6 or 1.7RR (10-13hp)
X-pipe (5-10hp)
Good Driving


I probably left out a few and some may disagree with my opinions here.

 

My first mod on any M6 LTx car would be 4.10 gears.

 

Oh yeah, good catch. Removed.

 

and question a lot of the other member suggestions.

 

This is "kinda" true, but mostly this is very misleading and basically wrong information....

While it is true the electric water pump still takes power and there is no free lunch.......what is different is the electric water pump runs at a constant speed while the mechanically driven ones vary with engine speed....

Benefit number one is the electric water pump is going full speed when the engine is at idle.....great cooling

Benefit number two is the electric water pump is still going this same speed when the engine is at redline......this is where/how the electric water pump SAVES horsepower!!!!!!

 

Lets not start the Elec WP arguement again!!


Leave it at the elec WP seems to add 6-8rhp on the dynos, true?

but LT4Bud is "more" correct.....

 

When an electric water pump is running, it is running at one speed, and they can design that motor to be its most efficent at that one speed. As an mechanical water pump is running, it is running based on engine rpm, and it has to be able to move sufficent amounts of water at 800rpm - 6400rpm. Its not going to be as efficent when the rpms increase.

Where as it may take 3hp to turn the alternator to provide the electricity to power the electric motor, as the rpms increase the mechanical pump may sap .05% or 15hp to turn.


The mods I would suggest would be these:

Hurst shifter and Hurst shifter ball. (no improvement in power, but really has a great feel. I wish I had done it sooner.)
Hella E-spec 100/80W headlights. (Again, no improvement in power, but makes the car much more enjoyable to drive at night/dusk.)
Headers. (10 hp? increase)
Electric Waterpump. (5 - 10 rwhp increase.)
Underdrive pulley (The only underdrive pulley I know of is the 10% pulley from ATI).

I personally recommend staying away from the lightweight flywheel. Some people have them on the board and don't have any problems, but when I had one in my car, it made the transmission sound like it had rocks and was falling apart when on the highway in 6th. I Hated it. I would stay out of 6th just so I didn't have to hear it.

Some cars dont seem to have problems with it, but the ones that do its really bad. You could easily spend $2000 if you swapped and found out you didnt like the way it sounded, and then swapped back to the stock flywheel (which is $800). In my opion its not worth the risk, and you can do other things to the car for more power with less risk. I would rather save the money and apply it to internal engine work.

I bought my car with an alum flywheel, and it really wore on me. I hated it so much that I bought a stock flywheel and had it put in.

 

4.10's are without a doubt are the best starting point to improve the fun factor of an LT4....

 

Although it wasn't my 1st mod, it should have been.

 

Awesome!

Question,
what brand of gears did you go with? (Dana-spicer?)

 

Dana 44/4.10 Viper gears...at least that's what it says on the receipt. AZ Differential in Phx did the internals (and supplied the parts) and the ZFDoc did the swap.

 

Sam - check out Rearend Specialties in San Jose. They did the 4.10's on my old LT4 as well as my old Mustang. The use Richmond gears, which will whine at first, but once they're broken in, they are great.

As for bolt-ons..... if I had to start over with a stock LT4:

EM headers
RT cats
Corsa Catback
4.10 gears
Hurst shifter
Electric water pump
1.7 rockers
Custom cold-air intake (modify the Callaway Honker to fit)
Custom tune


The above mods should get you around 330-340rwhp.

 

ported heads and the hot cam with the 4.10 gears and you won't be sorry,it will scream.melrose headers are just as good as EM maybe a little less expensive.also a good tune.

 

Has anyone actually modified a Callaway Honker to fit an LT4???

I called Callaway about a month ago and asked them about doing this and if they thought it would work.........basically they had no comment except that it wasn't designed for a C4 and they had no plans for a C4 design....

TELL ME MORE!!!!! PHOTOS!!!!!

 

I believe that the question dealt with "BOLT-ON" improvements. Everyone gave good advice, but the only 'bolt-on" improvements I can think of are LT headers, RT cats, and a good cat-back exhaust. This will gain you around 20 rwhp. P.S. don't buy an airfoil or Vortex "ram-air" or you will be totally flamed. Decals on the other hand.....

 

a lot of you have said pulleys but i thought they didnt make any underdrive pulleys for LT4 cars? i called march and a coupole different companies and they said the LT4 had different pulleys and ones made for an LT1 would not work. i verified this by finding out the pulleys on the LT1 and LT4 DO indeed have different part numbers from the factory.

About the 1.7 rockers..... is this just a simple swap in a LT4? can this be done with the heads on?