Looking forward to learning something here because I don't know crap and am very aware of that.

I have a 1970 something 440 I want to build for both power and mpg. I'll pause while you compose yourselves...

Now that you have cleaned the coffee off your screen allow me to elaborate. I want around 500 hp ( more is ok too ) and the absolute best mileage I can get. I'm going to run a T56 to get those last two overdrive gears and keep my foot out of it unless I wanna play. That's where the turbo idea comes in.

It's my understanding that two engines of the same hp, one turbo and one not, the turbo gets better mpg. How much I have no clue but 2 mpg for me would be worth it. More is better of course. This will be my daily driver so thats why the focus on mileage.

For my build I'm considering one if those Holly Sniper EFI units for better drivability and tuning. I don't know if my turbo idea is a good one or not, I imagine it's all in the execution. The cam, the compression ratio and the boost I run, and the internal parts I use to keep it together. I do plan on overbuilding the block so I NEVER have to worry about it coming apart on me. I want to do this ONCE.

So to all you forced induction guys I ask this: What can a turbo offer me in terms of the performance I'm after and if it will indeed help achieve my goals, what equipment do I need to be looking at?

 

Turbo won't increase your fuel efficiency, just make power. And you may not need it if you are building an efficient 440.

A fuel efficient engine will have a mild cam, very good heads, good manifolds and fuel injection. You will easily make your 500hp goal with a 440 and a solid, efficient top end with good headers.

Your transmission plan is going in the right direction.

I think turbo big blocks are for making LOTS of power, for your goal an NA build will likely be cheaper, more fuel efficient. If you want to run a turbo on something to make power and get better fuel efficiency find a current gen hemi, slap a holley efi and turbo on it. You will still make more power than your looking for but you get all the modern doodads that help with economy.

Just up your power goal to justify the turbo 440

 

I'm happy to up my hp, just don't wanna lower my mpg being a daily driver and all. So let's say 600 hp with a turbo, what would my MPG realistically be driving it with a light foot? I was only saying 500hp because I know power is fuel, but if higher hp is needed to get the usage if a turbo, then so be it.

 

No idea, there are so many variations with combos you could put together.

What do you get now? Figure you can get 10-15% better out of the engine and another 10-15% with an overdrive trans.

 

It's it driving yet so I don't know what it gets at the moment. 10% gains to me could be worth it to me, and between the overdrive and maybe a mild boost at highway speeds, if I can get 15 or greater id be tickled pink.

 

The bsfc is much higher with forced induction, meaning it takes more fuel per hp in boost. A boosted engine out of boost isn't always the most efficient due to typically lower compression ratios, and the turbo/piping.

 

Good to know and that's something I'll have to keep in mind to build into the engine.

 

Whats the best and worst I could expect from leaving the engine stock and bolting up a turbo, but running appropriately sized intake and such?

 

Steve Dulcich did a basically stock rv 440, single plane street manifold and "rv" performance cam. They made 381/476. Then turbo to something like 480/600 I'll look for the exact numbers/specs later.

Assuming your car has a car engine, not an rv engine you'll do better than him. That engine was anemic, low compression, mediocre cam.

 

Definitely a misconception that adding a turbo will somehow improve MPG. The way you see it come true on factory cars is by going with a smaller engine then adding the turbo to make the HP needed. In your case, to get 500hp, you'd probably be better with a 340 or 360 then add a turbo. For 500hp 440, you would never need to turbo to get that. A 10:1 440 with decent heads and modern valvetrain will do that and then some.

 

Bill Murphy had a 66 fastback mustang he used for Land Speed Racing. After running a bunch of SBF combos and setting alot of records at Maxton. He installed an 80 ish 2.3 he ran it NA then added the draw though turbo. He reported with the turbo it got better mpg on the trip from OH to NC. I agree the key to seeing better MPG is a small engine that struggles at part throttle. The draw though carb might have had something to do with it as well?

 

If the turbo allows you to keep the trans in a more favorable gear it may help your MPG. But a good top end kit can do the same thing. Tons of variables.

@SleeksSticks do you have any details on the engine, what it came out of, compression, cylinder heads, etc?

 

It's probably an engine from a 1975 imperial. That's all I know right now.