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Old 09-24-2005, 01:01 PM
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Turbocharging a 350 chevy

Hey folks, another turbo question ... This time about doing a Chevy small block instead of the big block a while back. I'm looking at the possibility of doing a turbo setup on my S10 and retaining the carburator setup. I figure I could just use a pressure plenum to do that, but the question is, what turbo to use. I'm looking to use something that is readily available, that is, Powerstroke, Cummins, or Duramax turbo. I've heard the Powerstrokes are easier to deal with since they're Garrett turbos, but from what I understand, the Cummins is able to make more torque than the others with a much smaller displacement. Some specifications on my engine since I know those matter also:

350 - .060 overbore = 360 cid
2-bolt ARP main bolts
SCAT I-beam rods (550 hp rated), floating pins, capscrew ARP bolts
Forged, unturned crank
ATI balancer, SFI
B&M flexplate, SFI
Wiesco pistons, 10.2:1 compression (I know its a little high)
882 heads, bowl ported and polished real shiny on exhaust, gasket matched intake and light polishing, no bowl work, 2.02/1.60 valves
cam: 243/243 @.050 mech. flat tappet w/ .517 lift on both
Magnum roller tip rockers
Crane kool poly locks
RPM Air Gap intake
750 mechanical secondary carb (for pressurized box)
MSD BTM ignition box

For the intercooler setup, I'm probably going to go with an air-water setup so it's more compact up front of the truck (driver's fenderwell area).
Also, will use water/alcohol injection.

I don't intend to get things much more than 8psi boost with 93 octane, but maybe 11 psi or so with some race gas and the intercooler/h2o injection.

Maybe Chris would have some helpful info on why I SHOULD NOT use the carb/box deal.

Thanks.

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#2 Yesterday, 12:55 PM
Siggy_Freud
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re: Turbo 350 Chevy

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Carbed systems are going to be much harder to tune with a Turbo'd setup. You also will not have the ability to run a knock sensor to determine at what point the boost is too much for the timing/mixture. I would seriously think about an FI setup if your planning on running a Turbo'd engine.

Secondly, I dont think your boost goals of 8-11 PSI really warrant a water/alky injection setup. As far as I've read, thats somewhat old technology and isn't as efficient as other more modern setups. Running a good intercooler and keeping your mixture and timing correct, you shouldn't have much trouble with 8+ PSI.

Also, you are starting with some really high compression to be running a Turbo. It would be better to shoot for 9:1 or perhaps a tad bit higher for your intended boost range.

I am sure Chris will jump in with much more information (and possibly correct me on some things lol).

#3 Today, 01:59 PM
radracer43
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re: Turbo 350 Chevy

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Thanks for the reply. I think that I may need to make a new post though because after taking a second glance, it appears that my thread is in relation to the TH-350 transmission.

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Old 09-24-2005, 01:05 PM
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I couldn't figure out how to change the thread title, so I just made a new one. The above post is copied from the original thread.

Looking for some help on how much compression is too much for a turbocharged v-8 application as well as what kinds of issues would I run into by turbocharging a carb'd engine? I plan on giving a shot at building an air box for the carb to sit in before I shell out the $600+ on a Vortech/Paxton unit.

For clarity, I'm using GM Iron heads, and intend to run ~ 10.2:1 compression PUMP GAS. Will use water-air intercooler and water injection.
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Old 09-24-2005, 01:47 PM
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There are more and more people using carbs on turbo applications. From what I understand, the carb boxes are old technology and aren't really used anymore. Now guys use blow-through carbs. CSU (carburetor solutions unlimited) is apparently a great place to get a blow through carb. They know what they're doing. If you don't want to buy a new one, you can modify a carb yourself to work with blow through. I don't know exactly how to do it; but that info must be out there somewhere. Carbs can work well with turbos. You will probably need a wide band 02 sensor to tune it; but it can be done.

The best place for turbo information I've found is here:
turbo mustangs forum
They have a section just for turbo small block chevies. Also, they have a big section just for blow-through setups. Check it out.
Also, here's the link for csu:
CSU blow-through carbs
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Old 09-25-2005, 01:43 PM
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Hello,

Over 10 CR with factory iron heads is a BAD idea with a turbo. You will have detonation problems. But, whatever floats your boat on that.

The carb box will work fine, but a bonnet will be better. Carb setups are particularly sensitive to bonnet design and it is worth the money to get a good one. I am loosing alot of boost in my funky built bonnet on my engine. It looses over 2psi just due to turbulence in the bonnet, but my design is really horrible for anything other than looks.

A carb is fine for a turbo engine as long as you do your homework and build it right. If you are trying to use a vacuum secondary carb, I would drop that for a double pumper. It will work alot better from what I have read and seen.

EFI is definately a better choice, but it is also expensive so I understand. There are alot of guys running carbs with good results.
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Old 09-25-2005, 07:30 PM
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Thanks a lot for the input. The turbo mustang forum has really been informative and helped me understand all the things necessary to do a carb/turbo setup. Guess I'll be going with flattops (9:1) and just deal with having a milder cam than I originally wanted, at least until I get my turbo stuff together. Thanks again.
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