5.3L LM7 Swap into OBS

[L31MaxExpress]

I'd like to see the 350 make 400hp or so with just a cam and springs. The 350 in it's day was an awesome motor and for certain applications it still is, but to make the 400hp mark with a stock bore not very worked over 350 is unheard of. Advancements in design and cyl head flow are what ultimately doomed the 350. Yes you can get a worked over 350 to compete with a stock LS. But it takes a lot more work to get to that point.

I am shelving my 350 to swap in a LS for one simple fact, my truck is 26 almost 27yrs old. It's got an antiquated EFI system on it, it has 180k miles on a very well worn 350 and on a good day made 210hp at most. The LS I am swapping in while yes displacement wise it is 27 CI smaller it pushes out 270-295hp/315-335ftlbs in stock form, and with the mods I am planning I will see in NA form ~450hp/475ftlbs, Boosting it (Turbo) i'll see 600-700hp give or take. You cannot do that on a 350 as cheap as the LS. I think all in all in NA form I will have ~$2500 into the complete swap which includes trans (Th400), converter (3000stall), Cam (BTR Turbo Stg3), Valvetrain(BTR), Tuning(either myself or a local guy).

The LS is far from gutless. At this point stock for stock it is the 350 that will get walked.

400 hp is pretty easy with a Vortec 350. Cam and headers almost gets you there even with the truck intake. How high are you going to have to spin that 5.3 to get to 475 hp? 6,500? 6,800? Not exactly the torque curve I would want in a truck.

 

[0xDEADBEEF]

400 hp is pretty easy with a Vortec 350. Cam and headers almost gets you there even with the truck intake. How high are you going to have to spin that 5.3 to get to 475 hp? 6,500? 6,800? Not exactly the torque curve I would want in a truck.

LS is not super torquey off-idle, I think everyone agrees, but the LS torque curve in general is nice and it's got a nice mid-range pull that doesn't fall off quickly. Different strokes for different folks.

 

[L31MaxExpress]

LS is not super torquey off-idle, I think everyone agrees, but the LS torque curve in general is nice and it's got a nice mid-range pull that doesn't fall off quickly. Different strokes for different folks.

I'll stick with my 383. Lots of torque everywhere. 11:1 compression with 210cc heads flowing ~300 cfm and a smallish roller cam. Wraps up to 6,200 very quickly.

 

[0xDEADBEEF]

I'll stick with my 383. Lots of torque everywhere. 11:1 compression with 210cc heads flowing ~300 cfm and a smallish roller cam. Wraps up to 6,200 very quickly.

I feel like that's an apples/oranges comparison, but I'm sure it's no slouch. How would it compare to a 6.2?

 

[618 Syndicate]

I feel like that's an apples/oranges comparison, but I'm sure it's no slouch. How would it compare to a 6.2?

Or a 5.3 based 363 stroker.
A small block is a great motor, and so is the LS platform. Old tech is rarely superior to new, but some folks are unwilling to embrace change.

 

[618 Syndicate]

400 hp is pretty easy with a Vortec 350. Cam and headers almost gets you there even with the truck intake. How high are you going to have to spin that 5.3 to get to 475 hp? 6,500? 6,800? Not exactly the torque curve I would want in a truck.

I suppose that depends on what the truck is being asked to do.

 

[Wh4t3v3rs]

I'll stick with my 383. Lots of torque everywhere. 11:1 compression with 210cc heads flowing ~300 cfm and a smallish roller cam. Wraps up to 6,200 very quickly.

I can appreciate that build... had an 82 short bed with 383 PDM 220 cc heads, crower rods, ross pistons, comp roller cam, jezel belt drive....it was a beast! Love the 383, but if we are gonna keep up with the times and build a stroker, I'm gonna have to take the 6.0l stoked to a 408..... thats gonna give a 383 all it wants and some more..... imo

 

[L31MaxExpress]

I can appreciate that build... had an 82 short bed with 383 PDM 220 cc heads, crower rods, ross pistons, comp roller cam, jezel belt drive....it was a beast! Love the 383, but if we are gonna keep up with the times and build a stroker, I'm gonna have to take the 6.0l stoked to a 408..... thats gonna give a 383 all it wants and some more..... imo

At that point a SBC 427 would work at kicking the 408 in its pants. Dart 400 block stroked would be cheaper than a 408. Look at what even the 410 sprint car engines make for power NA.

 

[Wh4t3v3rs]

At that point a SBC 427 would work at kicking the 408 in its pants. Dart 400 block stroked would be cheaper than a 408. Look at what even the 410 sprint car engines make for power NA.

"I call" with the LS7 7.0l ..... apples to apples. The LS is here to stay!

 

[Erik the Awful]

I'd like to see the 350 make 400hp or so with just a cam and springs. The 350 in it's day was an awesome motor and for certain applications it still is, but to make the 400hp mark with a stock bore not very worked over 350 is unheard of.

Out of curiosity, what does it take to get a stock 5.3 to 400 lb/ft of torque? I'm not doubting that LS motors are the way forward. I'm a 350 fan simply because they're cheap. Also, I'm hopeful that my stock-headed, 4.000" bore 350 with a cam and springs is around 400hp once it's tuned. Everything I've read says yes.