jjc839

Yes, 250hp at sea level, that's how aircraft engines are rated.

Atomic

iTrader: (42)

Heres basically the most badass NA LS engine out there, RHS Turn Key 502c/810hp | Golen Engine

And its still not even close at 2500rpm. However if you look at the dyno graph, it does make 550ftlb at 3500rpm. You might could make something like this work if you use a smaller diameter prop with a higher pitch or more blades so you can turn more rpm, but as far as your original goal of 350@2500rpm or even 250@2500rpm does not look doable with an NA LS...

sand man

how much are the speed reduction units?

you might get an alumnium LS engine and youll save 80lbs compared to the Iron block .

2500 RPM @ .75 reductun will give 3333 RPMs engine speed

LS motors can stay there for a along time and prduce a decent amount of power

LS7 would be the best to go with

dry sump ready , light weight rods , has the displacment , and with simple mods will get you close to what you want

here is the dyno

its almost 230hp at 3000rpms

and on 3500rpms it has more than 250hp

Dyno LS7 Engine (17802397) HP, Torque RPM Chart | GM Performance Parts


with 2" headers , a custom cam , and a good tune , you should move the curve where you want

blackcash

I know a guy who thinks he's perfected an LS reduction drive. And he's wrapping an RV-10 around it. I have his card in my flight bag at work. I can not see a feasible way to make enough power, reliably, with that low of RPM. And I'm not up on FAA rules, but I know Transport Canada would never allow an STC for it, so you're stuck as Experimental. Which kind of sucks, because a 182 with an LS3 would be great.

An O-540 is roughly 440 pounds dry, I imagine an LS3 is not far off. Definitely under 500. But since the 540 only makes 300 or so, and the LS3 is 400 or so, you've already beaten the weight vs. power. Without throwing the W&B off too much.

jjc839

Ya, I just wish I knew more about engine design, it just seems to me that an O-470 should be able to be outperformed with a little smaller modern engine (say an LS stroker of some sort in the low to mid 400ci range) especially from the efficiency aspect of modern injection and tuneability.

An RV-10 should be a rocket with that motor, there are several out there cruising at 200mph on 235hp. There was an RV-6 or 7 for sale in Canada recently with a 4.3 chevy v6, carbureted with a PSRU that claimed 175mph cruise on 7.5gph.

It just drives me nuts that a new cessna 172 is ~$350k and you are essentially getting the exact same thing from 1956, just some updated avionics. That's why I really like some of the stuff being done in the experimental world.

blackcash

I was just talking about this the other day, that how much further ahead we'd be if the big companies would keep up to experimentals and home builts. The problem lies in the cost of something becoming certified by the FAA. However the FAA has delegated certification to the ultralight manufacturers to do in-house. It's on a trial run, but if it proves successful it may find its way up to Cessna, Piper etc.

The company I work for has six 172's, two are 69's the rest are 74's. You're right, you can hop in one of those, then go hop in a 2013 model and the only difference? Glass panel. Which shouldn't be in a 172, but that's another discussion.

Isak81

I would go with a stroked 6.0 and top it with the smallest runner heads i could find. It would keep the velocity up at low rpms. A good intake and professional designed headers would get you close. Having some one build tuned headers for your engine setup would bring the torque curve down.

smoggist

Just tossing this out there, but what about a reverse split cam? They've proven to make great power in the lower RPMs. Combine that with the small runner heads mentioned above on a Stroker an I'd think that would make pretty good power down low.