Need help deciding on what size turbos to get.

[Project69]

New to turbo field so some help would be great. I got my el-chepo headers coming and now i need to buy the turbos. What size would best suit my needs? Im guessing some info is needed.

Im looking for atleast 650rwhp, with good street manners, yes its gonna be intercooled also. Ive got a 383 with forged crank and pistons. 5140 rods. 9.5:1 compression. its gonna be carbed. Any size and company reccomendations?

Also if you need any info let me know.

Thanks

[DeltaT]

It's worth getting Corky Bell's book on turbocharging, "Maximum Boost". It has a lot of sizing and layout info, materials, intercooling and more.

Jim

[matty b]

whats your budget on them? theres a cheap not so modern style turbo that works just fine IMO and then there is the gt ball bearing hottest thing since 14 in brakes turbos. Cost is about twice for the cool ones that spool faster. Also are you looking for 650 wheel hp or 650 crank hp? And what kind of power band do these need to stay in? I ask cause you could get a smaller turbo that will be pushed a bit harder but will come on like a roots blower but you may have traction issues or you can go for a larger exhaust side that will really keep truckin at the top end. So I guess what is gonna be your main use of the car and what engine characteristics do you want? The carb and Im assuming distributor based timing is gonna cost you some hp cause to be safe youll have to run safe settings that can be compensated for with efi. Really a degree of timing can be worth 10-20 hp so your gonna have to push the turbos more and keep it rich and low on timing to make the power and stay safe. Fill in those blanks and I can probably get you in the ballpark if not the infield so to speak. As far as suppliers I only run Garrett turbos so take it for what its worth.

[Texas Hotrod]

650 rwhp won't be a problem, even with a conservative tune.
I built a system using Master Power T-70s on a 406 small block. It has excellent throttle response and little/no lag. It'll light the tires in 2nd at a slow roll and spin 'em in high gear, and that's w/drag radials.
The bigger cubes makes up for no-boost power, and when it spools up, it hits hard (scary fast).
You can't just throw on a set of turbos and expect it all to work, but boost is boost. The more you make, the better it'll go (and the easier it'll blow). The whole car has to be a complete package. If you put down 600+HP, the tranny, axle, suspension, brakes, etc... all have to be able to take it.
Then there's the electronics and the fuel system.
One major problem that I see is your compression is way too high. You need a maximum of 8:1, less is actually better.

Any pics of your project matty b???

[ZZ4Blazer]

I agree 9.5:1 is a little bit high, but 8.1 is a bit low as well. From the research I've done, even small increases in compression make a noticeable difference in spool and response. Id shoot for 8.5-9.0:1 with aluminum heads. I would go lower if you plan on iron, but I wouldnt recommend them.

Generically sizing, around a pair of T60's. There are litterally hundreds of turbo combos you could run now a days. Between different blade designs, housings, ball bearing or not, etc etc.

Turbos will make a ton of tq, Id shift them to come on a little later in the midrange with a little larger exhuast housing. Little bit of lag, but should help get you moving for better traction. But, when they come on hard its "like getting hit in the ass by a freight train". I dont have my turbo project running yet, again thats just from the info that I've researched. Id rather have the midrange/top end power personally. Depending how your combo is built, should also give you very "stock like" driveability just cruising and out of boost.

theturboforum.com has a ton of info as well.

[my72vette454]

I have had my twin turbo 468 powered vette on the road for over three years and I love the way it works. Keep in mind that my car is not a drag racer but just a street cruiser. I got 14/15 mpg before the turbo install and if you drive it decent, it will get the same mileage. The boost comes on about 2500 rpm's and when it hits you better be paying attention as it does come on like "being hit in the ass by a freight train". But around town driving is a dream as it behaves like a mild 8.5 comp big block, you can even get on it a little and nothing unexpected happens. The wife is scared of it now but I told her, just dont floor it and hold it there to the count of 2 and you will be fine.