Jachin99

What mods would i need to get to that kind of hp. would it still be a good street car or would it be too much to handle at that point. Would it still be able to take turns and handle alright or would it just want to fly out from under me. thanx.

MasterZ28

new camshaf and heads should get you up to 100HP more than your current hp numbers.
are you interested in turbos or superchargers? they can give you bigger numbers or you can build your way up with basic mods right into getting a complete new aftermarket suspension system.

JakeRobb

The amount of horsepower generated by your engine is not directly related to your car's ability to handle. There are suspension modifications that a lot of guys will make that are specifically intended to improve off-the-line traction at the drag strip, and most of those modifications will hurt your handling ability.

There are a bunch of ways to get to 425hp, but first, we need to know if you want 425hp at the engine (bhp, which is how cars are rated from the factory) or at the wheels (rwhp, which is what you get when you measure horsepower on a chassis dynamometer).

Once you have your 425hp, what do you want to do with it? Are you building a race car? If so, what kind of racing? Or are you just making a fun driver for the street? How much do you want to spend?

I'll go ahead and assume that you want 425rwhp, and that you want it for a street-driven car. There are six possible approaches:

1. Nitrous
This is by far the easiest way. Assuming your car is in good running condition and making average power for an LS1 with your mods, a 150-shot will put you a bit past 425 at the wheels -- probably closer to 440-450. This will put a large strain on your engine, and without further modification will most likely eventually burn through a piston, but you could go years without that happening.

2. Camshaft upgrade
To get an honest 425hp, you're going to have to go with a fairly aggressive cam. It will be a bit lopey at idle and not very nice to drive at low RPM, but it will make beautiful sounds and go like a rocket at high RPM.

The most I've seen out of a street-driven cam-only LS1 was 414rwhp, and that was through a manual transmission with full bolt-ons and a dual exhaust.

3. Heads and camshaft upgrade
By also upgrading the cylinder heads, you can go with a less aggressive cam for more a streetable result. You can have your stock heads ported, or you can buy a whole new set. Either way, plan on doing a cam too.

4. Stroker motor
By changing to a different crankshaft, you can increase your engine's displacement, going from the stock 346 cubic inches to 383, 396, or more. Plan on doing heads and a cam too.

5. Supercharger
With a supercharger, 425hp would be cake. There are kits available that make this fairly easy.

6. Turbocharger
There are also turbo kits. You can build your own setup for a lot less money, but it's not an easy task. All other things being equal, a turbo setup will be more efficient (i.e. make more power) than a supercharger setup.

Regardless of which of the above you choose, there will be supporting modifications you'll want to (and in some cases, need to) make. Fuel injectors and a fuel pump are a must, along with getting your PCM tuned to take advantage of the modifications. Headers, a Y-pipe, and a catback exhaust are highly recommended (or, for even better results, switch to a true dual exhaust setup with an X-pipe).

There are also a number of bolt-on modifications you should consider. I see that you already have an airbox lid. Other things to consider are underdrive pulleys, and an LS6 intake manifold (or, if you're going with a turbo or supercharger, the FAST LSX).

In all cases, 425hp is enough power to put your rear end at risk. If you mount a set of drag radials or slicks and do any hard launches at the drag strip, it could break. You can reinforce the stock one for a few hundred bucks, but it will still be relatively fragile. $2000-2500 on a 12-bolt or Dana 60 rear end will fix that.

Your stock transmission should handle that power level reasonably well, but you should consider upgrading that too. We have a supporting vendor here, Cahall Performance Transmissions, that will do a performance rebuild for $800 plus the cost of whatever hard parts might need to be replaced. That's the way I'd go if I were you -- Frank Cahall is very good.

I guess that's a good enough place to start. Let us know which of the above interests you, and we can go into more detail.

slomarao

you can do it with just a cam but its going to be a big one. My advice would be heads and cam.

Jachin99

My goal is to have a fast street car. im looking for around 425 at the wheels but if i fall a little short of that number, i can live with it. I have a NX express wet universal gm kit just laying around but if i were to put it on, i wouldnt want it to be my only power adder, so lets shoot for the 425 number without it with an engine/drivetrain strong enough to handle a 100 shot at the track every now and then ( probly a couple of times a year at the most). Can it be done with ported stock heads, a mild cam and this exhaust and intake?

http://www.texas-speed.com/shop/item...id=181&catid=8

http://www.sdparts.com/product/FAS54...ottleBody.aspx

I know with the nitrous i would need to upgrade the entire drivetrain. what parts should i look for? Btw i would like to keep this as cheap and easy as possible. i dont have all the cash to do this now, but im just planing everything out so i can get it all as i go along and dont make any wrong purchases. thanx

danhr

i have 415 rwhp though a 9" and my car is very streetable.... I still get 27 mpg.

I just have a cam and bolt ons

JakeRobb

Ported stock heads and a cam will definitely do the trick. When you say "mild" cam, what do you mean? Easy to drive on the street? There are some cams available that sacrifice almost nothing in drivability while offering huge power gains.

I wouldn't bother with the LSX intake for the power levels you're planning. An LS6 intake will be a lot less expensive and should be fine.

Pacesetter headers are fine, but they don't have equal-length primaries, which means they are not the best for power. Also, they're made of mild steel, so they will rust. Personally, I'm a fan of QTP. These are made of stainless steel and use equal-length primaries. It's more expensive, but worth it IMO. If you do get Pacesetters, make sure you get the ceramic coated option.

Along with the headers, you're going to want to upgrade the rest of your exhaust. This is a good option:

http://www.texas-speed.com/shop/item...d=196&catid=56

Finally, don't forget a tune. For the mods you have in mind, a mail-order tune should be fine, but if you want to pay a bit extra, a dyno tune is always best.

When you go to the track, do you plan on using drag radials or slicks? If so, you're going to want to replace your stock 10-bolt rear end with a stronger one. A 12-bolt or Dana 60 is your best bet. Strange and DTS make bolt-in versions of both for your car -- either would be fine. A Dana 60 is a little heavier, a lot stronger, and a bit less expensive than a 12-bolt.

As I said before, you'll also want to send your transmission off to CPT for a performance rebuild. Your stock driveshaft should be fine at these power levels, but while you have everything apart, you'll want to install a driveshaft safety loop.

Jachin99

When i say mild cam i mean something that i can throw in there and only lose a couple of mpgs and still have a car that is easy to drive on the street. With the exhaust im going to try to keep the egr and air bosses and keep the cats, and hope i can still pass emissions, even though an aftermarket exhaust will still have the moved, so if i do go with a true dual setup, i will still need cats. What i want is an exhaust setup that wont restrict my other mods. What i dont want is a setup that is going to rust and guarantee me that ill fail emissions. Which cams should i be looking at and where can i get an ls6 intake and maybe a set of stock heads to port for cheap. havent really thought about the tire setup yet. i guess ill go with something cheap that i can throw on for the track when i go now and then.

danhr

Things to consider...

Mild cam... a 232 cam max.... i'd go w/ a 224 cam to retain driveabilty (like I said in my earlier post, I have 415 rwhp through a 9" and I have a cam only 224 cam)
set of ported 5.3 or ls6 heads
ls6 intake, port/polished stock throttle body, decent set of headers (honestly... don't cheap out on headers... i prefer kooks myself...), decent flowing catback... personal preference here, POSSIBLY new pushrods, valvesprings, and a lid.

Top that off with a good tune (don't waste your $$ on a mail order... it's only like $100 more to get a dyno tune... don't half *** something that's important).

Things you will need to effectively use 425 rwhp:
Converter
built transmission.... lots of ls1 guys use flt and performabuilt
rear end... 9" is a great bang for your buck and is damn near indestructible
driveshaft... the stock aluminum one is very flimsy..... i've broken my fair share with a 325 rwhp car... you are going to have 425 rwhp
tires/suspesion.... you can make an entire new thread for that topic...... it would get fairly indepth

danziger

If this is going to be more of a street car than a track car, I'll vote for a decent MATCHED heads/cam combo with the supporting bolt-ons. I'd also put some money aside for a 3000ish rpm stall and shift kit/cooler/etc.
My old heads/cam combo made 436/420 with a 234/236 nitrous cam and some now obsolete heads. In your A4 car that would be around 420rwhp and there are lots of better component choices out there now.
Your tune will be crucial to the car's performance...

teke184

"like I said in my earlier post, I have 415 rwhp through a 9" and I have a cam only 224 cam"


i think just about anyone will agree that those results are FAR from normal.

most 224 cams fight to aproach 400rwhp with an m6 and stock rear...let alone auto and 9"

JakeRobb

Assuming you're buying bolt-in-ready, pre-assembled rear end kits, I'm going to have to disagree with the 9" being great bang for your buck. Of the three common options (GM 12-bolt, Ford 9", and Dana 60), it is the most expensive, and it's also not the strongest.

A Dana 60 is the least expensive and the strongest of the three. It's also the heaviest, but at only 25 lbs more than a 12-bolt (which is the weakest of the three), that doesn't seem to be a big deal to me.

Regardless, any of the three are more than strong enough to handle 425rwhp. I wouldn't even start worrying about a 12-bolt until 600rwhp, and in most cases it should be good for even more than that through an automatic.

Jachin99

So how much money is it to get the stock heads ported, assuming i already have them off myself, and where can i find an ls6 intake for cheap.

jmmullin

The port work is pretty expensive. I wouldn't recommend dropping them off to a guy that says he'll do them for $500... TSP can run a CNC program on them, but after shipping its about $1000 probably. And then you've still got to upgrade the valve springs too. Might just be best to look around on here or ls1tech.com to wait for someone that is selling a set of 5.3L ported heads. They would match well with the 224r cam that several have mentioned. I never really hear much about the 228r cam, maybe they don't make it anymore but I imagine its driveability and characteristics would be similar to the 224r, only with a slight boost in power/torque. Either cam would probably put you at your goal.

Whoever's putting 415 to the ground with a 9" and cam only, that is SICK. Either you're full of crap or you've got a freak! (or good tuner!)

And you can find an LS6 intake on ebay maybe, or in the for sale ads, from someone that is upgrading to a FAST. LS1tech probably has more stuff for sale and has a higher number of folks interested in GM performance instead of just Camaro/TransAm people.

Chrome383Z

And the car will be a ****ing pig.

425 through an auto is tough cam only. Even if you used a donkey dick cam the car will be a slug. 224/228/230 cars would walk it in the 1/4 all day long.

Some people get caught up in these cams and don't realize how much they lose in the midrange and how short their HP Peak is.

For a MS4ish cam only car to run with say a 230/230 car it will need a 5k stall + 4.56 gears in an AUTO.

A 230ish cam with 3.73/4.10 and 4k stall will run the same and be much streetable. Donkey dick cams are for high school kids.