Pender1

Picked up a bone stock high-mileage L59 to swap into my K5. I'm wondering if 400-450 lbft is a possible/reasonable goal on stock parts (short block and heads). I've got to pull the valvetrain apart anyways, so now's the time to do it if I'm going to change springs, cams, etc. This is a semi-off-road truck with a SM465, so <4000 RPM is the world I'm going to live in.

Ls7colorado

iTrader: (3)

stock cam and a tiny turbo that will spool very quick.
or maybe a LSA type positive displacement supercharger

Any cam swap is going to raise the power but it will be raising the power in the higher RPM range.

if you wanna stay N/A a Tbss intake (or 08-13 5.3 intake) will help some down low, long tube headers, and compression...Even with all that 400ftlbs below 4000rpm is gonna be tough and im talking flywheel numbers
Other than that your gonna need more cubes

Pender1

I'm not opposed to a supercharger, but that would be way down the line. Not enough budget for that in the short term. Not a fan of turbos. I'd prefer to stay N/A for now.

I'm sure 400 is a lofty goal, but it's my "perfect" build for the application. And yes, I'm talking numbers at the crank.

KCS

iTrader: (20)

400ft-lbs might be a little tough with that compression and displacement.

Ls7colorado

iTrader: (3)

What gear and tire size are you running? the right gear will fix your torque problem witch you already know im sure.

Pender1

What would you call an achievable number?

Pender1

Yes and no. You can't make up for no power without sacrificing drivability. Tires and gear may change at any moment, I've already changed them twice.

Ls7colorado

iTrader: (3)

Right but since these engines operate at a higher RPM a lower gear would be necessary to get the engine up to its happy range. Stock is about as good as it gets without forced induction for anything below 3000rpm or so.
You could get a set of 4.8 pistons (flat top) and mill the heads to get the compression up to around 11:1, get a set of long tubes and a 08-13 5.3 intake. That would probabaly get you close to your goal and make the most torque I can think of without shifting the power higher in the RPM range with a cam swap
Maybe someone else has some better Ideas

ddnspider

iTrader: (26)

You need a positive displacement supercharger in your life for off idle to 4k power. Turbo and centrifugal blower are tough to size to make a ton of power that low unless you intentionally size the blower pulley really small or under size the turbo.

Utinator

This cost just a little more than a heads/cam package:
https://boostdistrict.com/collections/truck-kits/5-3

Pender1

Yea, that'd be nice, but way out of my price range.

And good lord do they need to hire a website person. That thing's fugly.

Utinator

My heads/cam swap cost me around $3500-$4000 with labor. I think the parts were around $2500. You can do it for less if you can do the work yourself. The parts for a cam swap are about $1200-$1500 alone. Heads can run anywhere from a few hundred to a couple thousand. It all depends on how you do it.

If you really need that much low end torque, then the roots style blower is your best bet. Those LSA superchargers won't fit in my car. If they did, I'd probably have one. I love torque.

Pender1

My whole thing is I don't want to have to buy new heads. I'm doing all the work myself up to the point that I have a CNC and lathe, though I'd call myself amateur at using either. If it was affordable and fitting it under the hood was the only issue, I'd take a cutoff wheel to my hood in a second. Not like the paint on it is any good anyways.

ddnspider

iTrader: (26)

This can be a done with the right size turbo too...

LSleeper1500

You say K5 so I immediately think of at least a 29" tire up to a 35". With that alone, damn near impossible N/A. Even a decent 6.0 would be tough to get there. Throw a decent turbo on it and roast em.

Pender1

No offense, but what does tire size have to do with crank HP?

LSleeper1500

Missed the crank part. But what're the chances it'll be on engine dyno? Waste of money just to be disappointed honestly with a n/a build

Pender1

It'll never see a dyno most likely in any form. 450 is the max torque I am comfortable putting in before I have to start upgrading other parts of my driveline. So in a perfect world I'd get exactly that and WHP would just be what it is.

LSleeper1500

that much torque won't come from a 4.8/5.3 in NA form unless it's a crazy radical build. 12+ Compression, crazy heads, etc. Boost it or at least go to a 6.0 or 6.2 for those goals if you're staying NA

Ls7colorado

iTrader: (3)

yea because 451ft lbs will destroy everything!!!! lol

Seriously though what engine is in it now?
What do you plan to do with it?