First question, how do I get to 400hp in a LM7? I have shorty headers, stock cats to a 3in 3out thrush and stopped right there before the axle. I'm thinking intake, cam and tune should be close? Then, what besides tie rod sleeves do i need to hold a 4wd launch? What torque converter do i need? I pull a 16ft car trailer about once a month with various loads. Would like to retain a reasonable budget by using parts off other ls motors if possible. Also am rooting for around 15 mpg if possible. Thanks in advance.

 

What's your budget??

I'd switch to long tubes instead of shortys to give you the best flow. A intake tube for sure, the stock truck intake manifold is perfectly fine.

How big of a cam to you want to go?? That also plays into what stall converter you will want. Most of the mild cams with a good tune should put it real close the 400 crank horsepower.

Also remember that the stock 4L60e is rather weak and likely won't be happy with more power. And the factory G80 diff is not great either, swapping for a better limited slip is a good idea.

 

i plan on 4wd launches do will i have to crack into the front diff too? Budget is fairly low, like less than 700 probably. not planning on longtubes, would like to stay with shorties if possible

 

Cam wise i think i want more torque and really would like a good sound

 

You won't get much with $700, that will likely only cover your camshaft, bolts, gaskets, lifters and minor odds and ends. Don't except big power but some because you'll have to stick with a smaller cam. Then it needs a custom tune done and that's more money.

Front diff is fine, I don't see you needing to 4WD launch this thing with good tires.

 

20x12 wheels with small tires, it spins them now when you launch it, with 100 more horse it should destroy them. Im not worried about the tune in the $700. family friend has a shop and he offered to tune it in trade for some work. Yes he is reputable and has a awd dyno in house. i need 400+ hp. leave the tune out of the cost and tell me how to get there lol

 

I won't tell you much past what I already did.

This is going to take all the research on your part, you won't learn anything if it's just handed to you.

Research cam sizes and what is popular. Your cam selection is going to be slim because you only wish to spend $700 and that won't even come close to being enough to cover the cost of a after market stall converter added on.

 

nitrous bam done

 

Are you talking 400 to the wheels or 400 at the flywheel???

 

I had the comp cams xr275hr 222/224 .566/.568 112 and through stock manifolds and in a lifted truck was at 348, grabted that was in a 6.0 bored .030 over with l92 heads but i honestly think wheel hop/axle wrap were killing my numbers along with a screwed up torque converter.....