Inliners International Forums General Discussion Hi Performance Turbo or N/A

I'm almost positive that I've asked about this before but I would like more detailed answers on why.

Which would be better to run for a daily driven fun car? Turbo 250 or high compression N/A 250? Would you be able to make anywhere in the 350-400hp range with a high compression 250 without running race fuel all the time? What are the mpg differences? Which is more reliable?

Snowman,
To my way of thinking a N/A 250 or even a 292 dosn't make enought Torque to make that amount of HP unless you turn a lot of RPM. Remember [Torque X RPM = HP] so you would need a very good head, cam, valve springs, high compression pistons etc. to turn the RPM needed fot that HP.

With a turbo you can use a rebuilt stock 250, I would use forged pistons and intake springs 15 lbs stronger on the seat than stock, but thats all you would need to change. Whatever the stock torque of a 250 is just multiply by the density ratio of the turbo.

IE: 200ft lbs torque X 1.7 = 340 lbs torque (15 lbs boost).

Harry

Just off the top of my head.
A 12 port headed 250 w/ about 10:1 compression mild cam ,good street manners,could be daily driver,made about 320 HP @ about 6000 RPM (dont quote me exactly, going from memory )
That's 320 HP running mechanical FI downdraft throttle bodies $$, 12 port head $$$ & that's on an engine dyno, not HP @ the wheels.

Tlowes make shift thrown together turbo dyno flog made 346 HP @ 5000-5500 RPM (as a guess) & much more torque & torque is what you really want & can really feel (set of the pants feel)
*Note: that was w/only 6 PSI?

I had a 12:1 motor w/ DCOE side draft Webers for a daily driver, & it was a kick a$$ fun car to drive,but really practicle?,not so much , but I made due w/it, & it was my daily driver.I had a blow through Paxton set-up running up to 9 PSI, fun to drive, sure, but it was sluggish down low until 3500 @ up when it was on the cam & boost was up, faster than the 12:1 engine ,but not down low.

The Paxton was ball driven & was RPM limited.
I made different size pulleys so & would have full boost by 1500 RPM, but could only spin the engine to 4000 RPM & w/4:10's, could not run a full 1/4 mile, but was really fast w/those higher boost pulleys.
But faster than the 12:1 engine.

So in short,once you go blower or turbo, you will never ever never want to go back to normally aspirated.
Get that turbo project going!

With a turbo low boost & if you can stay out of boost will be decent on gas & very reliable.

But once you are boosting 12 PS & up, your mileage will not be great.

MBHD

Thanks for the detailed answer guys.

@MBHD, yeah I suspected the answer you guys gave. My boss was heckling me about how "all the young kids just slap on turbochargers and superchargers" so I just thought I'd double check.

If you choose to use a vortec 4200 you will be a lot closer to you goal in stock form.

Take a late model 4200 port the head on the exhaust side and add headers (custom fab job) and you will be very close to 350HP.

This is NA, add a junk yard turbo at 7 psi (very doable on a stock 4200) and you have 425 HP easy and still run pump gas.

well I wanted to use the 250 because it's original to my car. But I have looked into the 4200 before and I might use it in some other project when I'm older. Is the 4200 MPFI stock?

Is the 4200 MPFI stock? <<< yes

snowman4839,

I would not be too concerned about HP numbers.
Torque numbers for your application of the turbo engine is where it is really going to shine when turbocharged

You will make more torque than a stock 4.2 engine when your turbo is on your engine, & depending on your supporting mods to your engine could make more HP.

So, just saying , with moderate boost your engine can make say 300 & more of course HP but the torque can be 320-380 or more depending on your boost level.

I know your are on a tight budget & installing a completely different engine, turbo charging it would not be in the plans of a low dollar budget.
If you do not turbo the 4.2 engine, it will not make the torque output of your 250 turbocharged engine.

So in short, your main overall goal will mostly be making max torque & that is what you feel, torque, & it will be torque in the low RPM range ,easy on parts.

At this point in your life it seems you should not be changing your engine for another engine that was not there from the factory, I say , keep it simple & continue on with your quest.

Goodluck.

MBHD

BTW, the 4.2 engine is a great engine & should be considered an engine on the top of the list for a transplant.

Thanks Hank. It's always good to have some positive reinforcement

I just thought I'd go ahead and ask about the 4.2 because I've seen them around on craiglist for like $1000-$1500 for a complete engine. I expected that it wouldn't be cheap but I'm just examining the other inline options. So now that I've exhausted all other options... Turbo 250 Project, HERE I COME