best reasonably affordable 3-5l engine for na tuning?

[aspetuck]

I would like to tune an engine between around 3 and 5 liters. I don't want to resort to forced induction, although as a last resort I'd consider supercharging. I'd be aiming at around 125-150 hp/l on high octane gasoline, but probably wouldn't use it on the street. That being said I dont want to rebuild it every 1000 miles. There's obviously nothing cheap about getting this much power out of the displacement n/a but I'd like to at least start with a platform that's not crazy expensive. What would be some options?

[Lycoming]

Sounds like you'll have to look for something high-revving. BMW I-6's are the first thing that come to my mind.

[flynfrog]

lsx!

[TurboLag]

S62B50 from a E39 M5 should fit the bill..

[FoxHound]

Sounds like you'll have to look for something high-revving. BMW I-6's are the first thing that come to my mind.

They're the first engines that sprung to my mind too. Fairly cheap to buy, but the issue of tunning can be prohibitively expensive. A friend got a stock 3.2 litre M3 engine and once you've removed the cat, and installed a racing air filter you are looking at 20/35 bhp increase for a reasonable amount of cash. After this, it becomes harder to extract "cheap" power from the engine.
Not sure of the specifics, but M engines are in a fairly high state of tune out the box.

He is considering forced induction as the cost is far cheaper and the gains (torque and bhp) are huge.

Nissans 3.5 litre V6 is one I'd look at...as used in the 350z.
It has loads of potential, and is run in a low state of tune for longevity. Increasing compression ratio's etc will see decent gains, then you can look at aftermarket nismo parts which are comparatively cheap when compared to BMW.
Sounds good too

[andylaurence]

That's a range of 375-750bhp. Quite a range! What's your performance targets? The Nissan/Renault VQ35/VQ37 from the Nissan 350Z/370Z is supposedly a lightweight engine (I know no figures) and revs to ~7500rpm in standard form. Getting to the lower end of your horsepower target (375bhp) wouldn't be much hassle, although 440bhp for your specific hp requirements won't be so easy. The engine's used as a base for the World Series by Renault and makes 480bhp there, but that's not cheap...

[Greg Locock]

I doubt he has any targets, looking at his previous threads he's gone from developing a plastic engine, to adding a pair of cylinders to an existing engine, to this.

[tathan]

I doubt he has any targets, looking at his previous threads he's gone from developing a plastic engine, to adding a pair of cylinders to an existing engine, to this.

You can really tell when school's out for easter

I don't know why you'd avoid charging the engine unless class rules dictated. For bang-for-buck specific output a 2JZ or an RB will knock spots off most things, certainly compared to extracting more power from e.g. an M3 engine (said as an M3 owner).