lt4obsesses

I have a 96 lt4. I am wondering about how to achieve 400 bhp. I am not a bottomless pit of money. I also want the aspiration to be al natural. Anyone here achieved this and how did you do it? Oh, yes, and how much did it cost you?

My thoughts are intake, exhaust, and cam with ecu tune. 160 thermostat of course. I believe the rest of the drive train will handle this type of power, am I right? Also, not being an engineer, what is a good streetable cam for this goal? I plan on taking my time, and doing most of the work myself.

bobmic93

What is BHP? If your looking for 400crank hp ,I think your plan can obtain that. For rear wheel hp youll need to have your heads ported also. Theres alot of LT4 that run mid 12s with 4.10 gears and headers. Its a great motor.

lt4obsesses

BHP is "brake horsepower" same as rear wheel horsepower. I want to keep the 3.54 gears. I am not really looking for a drag racer, just a mean c4.

Zix

400 BHP is pretty easy to attain on the LT4.

-Headers (EM, TPIS, Melrose, etc...)
-Cat-back Exhaust (not *really* needed, but sounds great!)
-Cam - the CC305, or Crane GM847 cams are very streetable and work well
-Tune (PCMforless or Ed Wright)

That should get you pretty close, if you get the heads worked over a little as well that'll easily put you over the top though, and it's not a bad time to do it considering the rest of the engine is already apart!!

The rest of the drive-line will be fine as long as you don't do any high-rpm clutch dumps on slicks!

Zix

I always though BHP was the same as FWHP, not RWHP. If you're looking for RWHP then you'll certainly need to have the heads worked over! I'd get in contact with Lloyd Elliot, or Advanced Induction...they should be able to get you to your goal.

vader86

Brake HP is the same thing as Crank or Flywheel HP, the terms now are used interchangably.

It is not the same as RWHP.

lt4obsesses

Thanks for the tips. It's good to know that I was on the right track. And thank you for clearing up the rwhp/bhp thing.:o

ScaryFast

There is a big difference on a LT1/4 car between 400 rwhp and chp.

If you're looking for 400 hp at the crank, the mods listed above will get you close (as stated by Strick). If you're looking for 400 at the wheels you have a long way to go.

You'll need to add ported heads to your list.
Most likely you'll need a fairly aggressive cam (more than the hotcam).
Headers are a must.
Larger TB is a must, at least 52 mm, maybe 58 mm

I would guesstimate $3500-5000 in parts, labor is cheap if you do it yourself

Depending on where you live and how you drive, those HP numbers will probably require some better cooling, both oil and water. A bigger radiator with an oil cooler is another $500.

There is another whole list of "while you're in there" mods. if you start the project.

Good luck, let us know what you decide.

rickneworleansla

Good read here.

http://en.wikipedia.org/wiki/Horsepower

DeBaGo

I disagree. I had a Lt4 trans am with only mod over stock Lt4 head and intake was the hotcam. It dynoed in the low 300's and I know of others that have seen around 320-ish at the wheels. My car also still had stock exhaust manifolds at the time. Never dynoed with long tubes, but car ran 12.5-12.7 at Gainesville. A stock Lt4 with lt headers and a nice cam should easily start getting towards 350-370 range. I thing the 400 goal can be achieved for under 2500.

ScaryFast

BTW, I built an LT1 to have more than 400 rwhp, blew it up on the track, and turned it into a 383 with well over that...

You can do the labor yourself as long as you have the tools. You'll need to pull the motor and have lots of room to spread out the parts. It's not hard if you are careful and take your time (what isn't?) and the guys on the forum can talk you through every step of the way if you have questions.

I added my signature to this post with a list of my parts. Your heads already have the 1.6 RR if I'm not mistaken.

rickneworleansla

I'm learning this now preparing for the heads and cam. I already have cooling, exhaust, headers, 52mm TB, etc.. Try adding up the price for new larger injectors, 58mm TB, new timing chain, new opti, new EWP, ported manifold + heads, cam, labor, and rental car, since it's my daily driver. This stuff can get expensive. Not all of it is necessary but... And then what if I don't do the bottom end now and brake something.

ScaryFast

We're saying the same thing...you have seen around 320 rwhp at the wheels with a cam. Add headers for $800 and you're up to 335. A more aggressive cam than a hotcam (for $300) and you're at 350-370. So to get to 400 you port the heads for about $1500-1800. A TB is about $250. Looks like a little over $3000 without valvetrain and stiffer springs to support the cam, gaskets, sealers, head bolts, header bolts, exhaust, blah blah blah.

You'll easily get to $500 on a job like this in extras.

ScaryFast

Oh yeah, I forgot about the injectors. For a 350 you can get away with stock 24#, but I'd upgrade to the FMS 24# or 30# ($230) for safety. Running lean will kill a motor.

Keep in mind the FMS 24# are really about 26# on a vette, our fuel pressure is higher.

Oh, and Rick don't worry too much about the bottom end. For my first build I used a bone stock 2 bolt LT1 motor and didn't do anything but clean it up. It handled the additional power of the heads and cam just fine on the track. I fried a rod bearing because I didn't add an oil cooler. Just plain stupid...

ScaryFast

Here's my post on the exact subject from two years ago.

Note post number 3 from Zix

Sound familiar?

Pay close attention to the 11th post from 500hp. I followed this recipe almost exactly and got over 400 rwhp.

Also, Masterspykiller on page two has some additional input.

And lastly, notice my last post at the bottom about finishing the car over a weekend. HA! Took over a month.

http://forums.corvetteforum.com/show....php?t=1195485

lt4obsesses

Your heads already have the 1.6 RR if I'm not mistaken.[/QUOTE]

Yes, the lt4 heads are equipped with aluminum comp cam roller rockers with beehive springs and are angled valves. The heads produce a 10.8/1 cr. The sae advertised hp is 330. Some say it's more like 345, but that's all conjecture. So I'm really only looking for 70-80 ponies.

So far, I've just modified the intake and added Bosch Platinum 4 plugs. This "seems" to have helped my throttle response and low end torque a little bit. But until I dyno, who knows? My next move is a 160 therm. and 8.5 mm superconductor wires. Then maybe the MSD coil. I figure that adding cam will be better if I have the spark light up the fuel. Then LT headers w/ high flow cats & mufflers. Maybe no cats since my state doesn't check that stuff The plan is to set up everything else for the cam swap, since the cam will require ecu tune. I really don't want to take the heads off if I don't have to. At least not this year.

Zix

The LT4 came with 28.8lb injectors, so for a basic heads/cam upgrade they should be able to handle things just fine. On an LT1 then yes you should probably upgrade them.

jonecap

My car dyno'd 329rwhp after long tube headers, high flow cats, catback, electric water pump, and dyno tune....oh...don't forget the airfoil...and the k&n. I've been told that cars with a lower gear like mine will typically show less power on the dyno...not sure I can explain why.

If you figure a 15% driveline loss to the wheels, that works out to 378 crank horsepower with the stock heads, stock cam, and 82,000 miles. If you are more conservative on the driveline loss estimate and figure 10% driveline loss, that's 362rwhp. I suspect a cam change would net atleast 400 horsepower at the crank with no other changes than the tune.

ScaryFast

Saw this on the FS forum - new hotcam for sale.

http://forums.corvetteforum.com/show....php?t=1654878

bobmic93

$2500 No way! Especially if hes paying for labor. Heads are big money.