Have a bone stock 4.8l. Going with 2 small turbos and I'm sure I'll have a cam speced. Anyone think it's possible to get 500ftlbs at or below 2000rpm's? Plan is to drop it into a 98 4x4 3/4 ton in place of a big block. Want big block low end but better fuel economy. I'll use factory manifolds as well as stock 862 heads.

 

not shure but the best I ever got was 420 at 2800 with a radix and 5.3

 

What psi was that? I'd like to run 7lbs.

 

I dont know... to make that much tq it will take a lot of boost with a 4.8 that may make 200 ft lbs at that RPM. I think it will be hard to hit that boost level at such a low rpm, but who am I to say its impossible. I'll let the more experienced turbo guys toss their opinion into the ring.

I guess at the end of the day my thinking would be this. If you can get the load on it I bet its possible... but real world environment it will be hard. Take a ford ecoboost or BMW twin turbo 3.0 for example... they claim stupid tq down low, but I think the tune will call for a downshift or revs will climb too fast to actually see their claimed tq at such a low rpm. Again I'll let an expert chime in here.

 

forget it... you wont make 500 with 7lbs at any rpm.

 

Maybe 10 psi? That's kinda trying to copy is the ecoboost. That's at the flywheel not rear wheel. Should have said that sorry.

 

Yup maybe. The truck is going to be actually hitting 10 PSI at that RPM.

 

I would rethink your goals, let the engine rev. Old big block heads died early, which is why they made torque so early (its more like a lack of torque late). LS heads are much better. Once the boost comes on you can push through the converter to wherever you want basically. 500ftlbs at 3500 is much more attainable and less likely to bend rods or detonate.

 

I made 500 ft-lbs to the wheels on a dyno jet last fall but at 4400 rpm. This was with my setup in my signature except for original Magnacharger heat exchanger and smaller collectors on my headers running 10 psi. With the larger headers and heat exchanger I am sure it is a bit higher by maybe 20 ft lbs or so.

 

Also the Eco boost truck. I drove one for a few days.
1st gear sucked. Was lazy in low gear
2nd gear was a blast.

Back to your goal.
Don't get stuck on low end numbers.
Making the 4.8 breathe better will help its torque.
Plus make torque to low you won't have anything higher up.
And guess where your rpms will be while pulling a load. Not at 2k.