I want to build a twin turbo 355ci sbc. I have some questions about Turboing a v8.

1st: Can I you use a Carburator with a turbo?

2nd: (topic subject) If so, does the carburator come before the turbo or does it sit on the intake like a N/A setup?

3rd: What size Carbs would you use for a dual 4bl setup?

4th: Ideal Cam?

5th: Ideal Compression ratio?

6th: Ideal size/type Turbo? I was thinking a sequental (sorry for the spelling) turbo setup with a small turbo on one side and a large one on the other coming togeather in a sealed intake pice right above the dual 4bls.

I have read many posts about this but none have the answer to "what is the proper setup?".
Many thanks for reading.
- Phil Johnson graemlins/beers.gif

Originally posted by gman:
I want to build a twin turbo 355ci sbc. I have some questions about Turboing a v8.

1st: Can I you use a Carburator with a turbo?

2nd: (topic subject) If so, does the carburator come before the turbo or does it sit on the intake like a N/A setup?

3rd: What size Carbs would you use for a dual 4bl setup?

4th: Ideal Cam?

5th: Ideal Compression ratio?

6th: Ideal size/type Turbo? I was thinking a sequental (sorry for the spelling) turbo setup with a small turbo on one side and a large one on the other coming togeather in a sealed intake pice right above the dual 4bls.

I have read many posts about this but none have the answer to "what is the proper setup?".
Many thanks for reading.
- Phil Johnson graemlins/beers.gif 1. Yes, you can use a carb with a turbo
2. Yes, it sits on the intake like a N/A engine
3. Why do you plan on using dual carbs? All you need is one good one.
4. Depends on set up/combo and usage. I'd suggest talking to UDHarold or equivalent/company such as Comp Cams, Crane, Crower, etc.
5. See #4
6. Sorry, can't help you there, but, I'm sure someone else here can
Good luck with your project, and I hope all goes well graemlins/thumbsup.gif

I agree with LXS about the single carb, otherwise youll have to convert 2 carbs to a blow-thru setup..also, the turbo size depends on the power you want to achieve. I assume youre planning on pump gas, so i would probably suggest a pair of T3's running abotu 4-5 psi each. The sequential setup is a waste of time...94-98 supras come with that setup stock, and anyone who tries to make decent power switches them out for bigger twins or a honkin' single. If youre worried about lag, Keep the exhaust A/R smaller, btu be aware that it could limit your top end. Also, i woild keep compression at abotu 8.5:1, and your cam will have a wide LSA (around 114) to help keep in the cylinder pressure....Once you find otu the intended usage, you can go from there...

Thank you for your replies. Please keep posting info if you can my fellow Chevy Freaks! (I mean that in a good way).
graemlins/beers.gif

EDIT:
What do you mean by converting a carb to "blow thru"?

All you need to blow thru a Holley carb is the styrafoam type floats. The hollow brass or plastic ones will crush. If the carb shafts are tight no special seals are needed. No air box is needed up to 45 lbs boost. If you want the most power possible go with 6:1 compression and a bunch of boost. Horsepower comes from burning lots of fuel with air, not from the compression ratio. While one carb makes things simpler, it is a restriction to air flow. Two carbs will also give better distribution. A mini tunnel ram, if you can imagine such a manifold, gives the ports and runners the ability to store up pressurized fuel/air mixture above the valves waiting for the valve to open and allow it to rush in. If you are thinking low boost (4-7 lbs) 8:1 compression and a single carb will work.

What size CFM carb to use for low bost set up with 8.7:1 compression? I curently have a Edelbrock RPM Performer intake, Holly 750cfm vacume secondaries, and a 2" spacer under the carb. Can I reuse any of these? Should I go with a bigger carb? does a carb need any type of extra fuel pressure device like a fuel injected car does, or does the carb automaticly add more fuel because of the pressence of boost? What size squirters to use? I think I've got the #31 squirters in there. The carb came with #28 and the car REALLY stumbled off the line. now it's better, but will it get worse with boost?
Thank you for all your replies graemlins/thumbsup.gif

If you use a marine type (sealed) fuel pump you can run boost pressure to the top of the fuel pump diaphragm to increase fuel pressure as boost goes up. The manifold will work (lose the spacer) you'll need a double pumper or the secondaries won't open, and any stumble or backfire you have must be fixed before you do any turbo work. graemlins/thumbsup.gif

what about the MSD fuel pump voltage booster (http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=4783&prmenbr=361)? is this only for fuel injected systems? I trust MSD products but is this for my setup? I'd hate to spend that much and it not work.
graemlins/beers.gif