I just made 450 through a 9", auto trans, with cats and 1 3/4 longtubes with the mamofied setup below...using a very reasonable cam...very nice drivability.

https://ls1tech.com/forums/dynamometer-results-comparisons/1601398-my-450whp-mamofied-1le-ss.html

 

I wouldn't worry about hp numbers. Just put on a good set of ported ls6 heads and a proven cam and you'll like it. You probably need to worry more about torque for road racing to get you moving coming out of the turns. JMO

 

In my ls1 I'm running a 383 kit with standard heads machined, 240's cam, 11.5 comp and under drive pulley kit, makes 460 hp and 884 ft/lb through a t-56 and 4.1:1 gears. Have a look at tsp, you can build a killer bottom end for only about 3.5 k, few hundred for your heads ported and then just add a cam and a tune

 

884 lbft of torque is really impressive even for a 383...lol
Predator-z probably has an el torro cam, a design of his that quite a few people have had good success with, and a set of badass worked 243s like livernois stage 3s or cartek 4xs. Stock casting heads can make great power if the right people work on them.
Just about any of the site sponsors here could set you up a package to meet your goal

 

Your biggest issue is probably going to be getting an exhaust to flow well enough to make that kind of power since you are in an M3 - your exhaust options will probably be quite limited (I don't know that for a fact, but probably a safe bet). Anyway, here is my build thread, I made 470/419 with it, and the setup traps 122 with a full weight Camaro.

https://ls1tech.com/forums/generatio...ld-thread.html

If you have any other questions about the build PM me. I doubt I will check back on this thread. Good luck.

 

What machine work was done to the heads?

 

Op if you're still in need of a powerful head/cam/ intake combination let me know. I have several different cams that would work great. We work with several head porters depending on the situation and application and the customers budget. Either of my street heat stage 2 cams with a nice set of ported heads will make average power for days and on a road course that average power is king.

 

I would do a headgasket set with a small size cam and nice valve job and call it a day. To many people over build their cars for road race duty.

I realize this is a M3 and not an Fbody but if you NEED to add any power and thats if you evem need to at all, cam-only will be plenty. You don't want to build the **** out of the motor to go flying *** down the straight away and burning the **** out of your brakes and tires just to turn around and do the same thing at the next corner. You should be focusing on driving faster not making the car go faster. It will be more rewarding that way too.

Just keep the power level close to stock as possible and focus on cutting better laps, that is why you got into road racing right? To challenge yourself?

Now if this was a street car.... go crazy, do as much as you want. 500rwhp is no easy feat for a 346, like your basically going to have to spec a perfect combo, even if your chassis might be a little more forgiving on the dyno (what differential unit are you using? Don't know much about M3 swaps). I assume that M3 will dyno about the same a 10-bolt or a LSX rx-7 so it will pull down good numbers but that is way to much for what I would want on a car that I took on HPDE events. A healthy ls1 with bolt ons MAYBE a 220-224 cam that is more than enough power to get that M3 moving and will have a nice power band too.

Put your money in tires.

 

450's very possible, i made Almost 420 rw with an F13 cam , and a set of long tubes, and intake and tune.. or you could find the deal of the CENTURY like a BNIB Procharger kit for $1,200...

 

Go boost if your looking for 500s,not easy to jit that # with h/c,or do a h/c ls3, blocks are getting cheaper these days,i would go boost,wish i would have from the start

 

Or you could go cam-only and make these numbers:

 

I still think your going in the wrong direction band aiding your lap times with brute power on the straits. You should be learning to drive your car to the limit. But I guess what I'm saying is less cool.

 

Or both!