Inliners International Forums General Discussion Blown and Injected Turbo Basics - Engine Planning

I'm trying to educate myself on installing a turbo with my 250 in my '68 Camaro. It'll be a street setup, bored 0.030", mild cam, improved exhaust and intake, TKO-500 or T-5 trans, 3.08 gears. Probably will be staying between 1500-3500 RPM. Looking for decent MPG (20+) with as much HP and Torque and fun as I can economically get. I have a few questions.

1. Will a turbo increase or decrease MPG?
2. What kind of cost am I looking at?
3. What improvements in HP and Torque should be anticipated?
4. GUT CHECK,,,,,is this a good idea considering the parameters of my plan discribed above?

your plan is good but alittle off target.

improved intake/exhaust is good and the mild cam also for a turbo setup.

the stick trans, 1500-3500 range and decent mileage are not good.

now to answer some of your questions:
1. a turbo will most likely decrease mileage.
2. cost of around 2000.00 all done with a carb. realistic
3.30-50% increase mainly in torq because of your low rpm level. a 250 will run much better in the 3000-6000 range for power. in this range the hp will come up sharply. and still provide good economy in the 1500-2500 range.
tom

These are the same questions I'm curious about except I've got a 4100lb truck in the equation. How will this affect me, especially #4?

witherer
2000 - 4800 RPM range is doable.
Pick a cam with about 204 degrees duration @ .050
Wide lobe center,115 .
I agree w/Tom auto trans is much better especially w/a turbo.
4 speed auto w/a lock up torque converter.

Use a smaller exhaust housing for the turbo.

I can see making 300 HP easy /w/a ton of torque of around 380-450 ft lbs. While running on pump gas & 15 lbs of boost.
I always recommend alky injection.
And some sort of knock retard system Like a J&S Safegaurd system.
http://www.jandssafeguard.com/

If you are light on the gas ,,,you could get above 20 MPG,,,, but w/a turbo,,,it will be very hard not to step on it, :-)

Brad,
it is a great idea,but it is not cheap.
You really need to go with fuel injection.

MBHD

witherer, I would put more cam and more gear personally. 220 at 50 w/ 115 lsa as mentioned, 3.55's with the big overdrive of the t-5. I think you'll like the car better.

And I second the motion for alky injection. If you are going to forgo the intercooler, I would say it's mandatory. My brother has a snow performance one at it works good.

I looked at the knock retard. It looks pretty cool.

I think witherer is looking for low RPM engine range ,,,wants a lot of torque.Plus gas mileage of 20 MPG or better..

220 Degrees duration @ .050 on a 250 CI engine.,would not be a good cam for low RPM range & 20 MPG.

Two cents thrown.

MBHD

Hi everyone- new member and new to L-6's-
I have questions along the same line. My idea is for an odd vehicle- 90 c1500 5spd. 3.73 gears (currently running a holley tbi'd 355 w/ (2) 60 #/hr's.) I have a ton of questions for anyone w/ info- first, can I adapt my tbi, cpu, harness, etc, or at least use bits and pieces on a 292? Just looking to build something different, looking for 300-350hp and similar torque (all my borg warner tranny will handle) for light towing and street use. Mileage is not a concern, but cost is. And I know the stick is a poor choice for the turbo, but I have to row my own!

If you have the underhood room, a drawthrough setup from the old 301" transams would be a snap, mounted sideways. Those turbos are good for 300 or maybe 330 horse worth of air. The turbine housing is a .82 A/R T3, and should be good to 4500, maybe 5000 on a 250".

Check out pics of turbo'd slants at slantsix.org. There are pics of that setup on a slant.

Dave

HI Dave, I'm over here trying to figure out a turbo size for a 292 chevy 6. I found one in a late sixties 3/4 ton chevy truck with a t-400 behind it. I'm trying to buy it now. If I don't get that one I'm going to build a 250. I think I saw that a 301 turbo setup in Leo Santucci's book. I want to do some headwork/valves, a cam, fuel inject it and build the exhaust header for a turbo.

I'm still in the chassis design stage, and the 500 cad is still in the wings.......john

Boogiemanz1-
For a street 292, a 60-1 with a .69 to .95 turbine housing (or similarly-sized T04B variant) will run real well, with a wide LSA cam (114+), mild lift, headwork, and a GOOD ignition. That combo will make lots of useable torque all day long.

As a side note- Spa turbo makes a cast turbo manifold for the chevy that is affordable.

Thanks for the info Jeff. Is your 4.2 turbo'd?
I bought a GM familiarization book and vhs tape on the 4200 engine.....I'm getting real interested in that myself........john

It's 'in process'... I'm in the process of fabbing mny parts.

Tlowe on this board also has the turbo manifolds. Better price, too.

I think the 4.2 may prove to be a more cost effective engine to build I saw a wrecked trailblazer on a repo site that went for 1200.00 and ran like new. Nodular crank powdered metal rods, DOHC with variable valve timing.....oughta run with a turbo on it........john

the word had it that Glen Self had the 4.2 @ 1400 turboed. He also had it in a Nova wagon.
I had a video link but no idea what i did with it.

http://www.1320video.com/dragweek.php

It is on 3/4 the way through the video.

Click on Day 2 link w/pic of Red Nova


MBHD

8.82 @ 155 MPH

MBHD