Undecided lsx 454 n.a. 700hp vs 408 stroked 2.9 whipple sc

[MAGONSTERZ68]

Any lsx454 owners out there able to chime in on living with LSX454 700hp range and for that matter any 408CU LQ9 Whipple2.9 SC owners sameish pwr?
Car is driven weekends on 200 mile loops to the coast so it see plenty of fwy and out of town cruising time.
On the fence on what power plant to go next, like the thought of both but have never owned either version, current pwr plant is 525HP LS3, its nice just time for more oomph. It will end up going into my 50 chev 1500 3-window stepside p.u. eventually.
Am a fan of bottom end torque and from the looks of it both can do both well.
I know iron block lsx is heavy when its all assembled the LSX 454 weighs about 570 lbs.
LQ9 about 520 dressed, add bout 160 for sc and jewelry, roughly 680? sound about right?

[Vimes]

Both are nice options, but since you're mainly going to be cruising I'll suggest you include a turbocharged 408 in the mix. A turbo tends to get better mileage when cruising as it's sucking power back out of the exhaust. A supercharged engine draws as much as 50HP off the crank, and a large NA engine needs a large amount of fuel all the time.

If you're interested in the LSX engines, Chevy also sells an LSX-376-B15 that's designed from the ground up as a boosted engine. NA it makes 473HP @6000 RPM and 444LB/FT @5000 RPM with a fairly flat torque curve, so it wouldn't take much boost to get into the 700 range. 15lbs of boost on a 473HP engine should get you around 950HP at the crank, so 9lbs should have you right around 750HP.

https://www.chevrolet.com/performanc...sx/lsx-376-b15

As to living with a heavy engine, you're gonna feel it up there. I've owned my share of big blocks and they tend to plow the corners when you're into them. If you go that way you'll want to move as much stuff as you can to the back.

[andrewb70]

Why not put a forged rotating assembly in your LS3, add a turbo friendly cam, like the Summit Racing Ghost cam, and a turbo? For a simple turbo hot side, Holley has a great cast manifold solution.

Another great option would be a LSA with a cam swap.

Andrew

[ryeguy2006a]

I'm not sure what my car makes since I haven't had it on a dyno, but I'm very happy with almost the exact combo that Andrew described. I'm running an LSA supercharged 6.2 with the Summit Ghost cam. Nice rumble at idle, tons of torque and really easy to drive. I turn around 2100 cruising at 75.

[MAGONSTERZ68]

Thanks for the input guys, and i did consider forging ls3 and lsa topping but at this point paired with built sonnax guts 4l60 it a perfect candidate for my 51 chev pick up swap.
I did consider single turbo 6.0 but with the hide away lights, RS hood opener latch and A/C it is a crazy tight fit in front not to mention the hotchkiss handle bars narrowing the room on manifold to fender well sides.
To boot I don't own the bend and weld skills to plumb in the hot or cold side tight enough to keep fender wells for convertible car rigidity and inclimate weather driving.
How is the under hood heat soak with the single turbo? Im firewall and floor insulate to the hilt and don't notice any now n/a.
Wonder if anyone has done a single turbo plumbing with this these handle bar subframe connectors in place, couldn't find online anywhere.

[Vimes]

That would be tight but I think a turbo would be doable up there, if it were put where the air cleaner currently is. There would be extra room if the power steering pump were changed to a remote reservoir. And I couldn't help but notice the huge holes in the hood, one of which would be right over a front mounted turbo so there's heat relief right there. But everything that's been discussed is going to add quite a bit of weight to the nose, which will affect handling.

Remote mounting would also be possible, by putting a turbo where the mufflers are. You'd convert to a single exhaust going from the engine to the turbo, then could run the cold side back to the front of the engine on the other side of the driveshaft. Hit an intercooler from under the car, have the intercooler outlet to the engine on top and you'd likely end up with the same amount of real estate under the hood as you have now. Remote turbos run about 500 degrees cooler than front mounted, and if you don't run high pressure you might not even need an intercooler although I'd still try to run one. For my own project, if I do forced induction it will absolutely be a remote turbo, but then mine's a truck and I have tons more room to work with. This option will also add the least weight to the nose, since the only thing up there would be an intercooler and a little extra piping with the turbo's weight back next to the rear wheels. Overall it'll be heavier, but you might even find the weight balance shifted to the rear by a percent or three.

But I have to ask, a convertible? I've heard of race-prepped convertibles being run at the track, then the doors either won't open or won't close because the body twisted, and the roof no longer seals to the windshield. Even with the extra reinforcement you've added I'd be careful about how much more power I added, particularly low-end grunt, because you don't want to spend the extra time and money, run down the track once or twice, then have to send the car out to be untwisted. You might even want to consider a Vortech supercharger, which is pretty much a turbocharger compressor side mounted to the crankshaft via belt. They don't come on until you've built some RPM, so should be less likely to twist the body around but should be good for a 150-200HP peak on a 400ci-ish engine.

[MAGONSTERZ68]

Thought about rear mounted remote turbo, car is lowered and already drags flatish mufflers and no room between fuel tank and rear axle so ruled it out.
will take a look at the pro charger if i can find a low mount that wont interfere with my suspension mods up top, Vert is not a track car by any means, just added bracing to remove inherent topless flex, so far so good.
Appreciate the the perspective, thx