Turbo requirement for 350 SBB

[gs_jimmy]

In the middle of a small block Buick turbo project. Looking to figure out turbo size on the boost requirements.

Rebuilt SBB 350 (8.5:1 cr, iron heads, GS cam)

Induction

- Holley blow thru carb
- Stock type single 3.8 turbo set-up
- front mount inter cooler
- Ford EDIS coil on plug (w/MSD 6A?)
- TH200R4 (stall?)
- true dual exaust - no cat (obviously will run a single down pipe to the X pipe, dual from there)

Mostly just updating the whole '69 motor to an '87 GN type set-up.

Next year will figure out the SFI system to complete the deal.

Vehicle is a 3500 lb 1969 GS California
3.31 12 bolt rear (Chevy style)
Currently running Stage 1 455 & 4 speed
"Passes everything but gas stations"

My goal is very simular performance, with the 22-25 MPG of a turbo car.

Had this car since 1982 and would really like to drive it more.

Any tech advice would be great (other than drop a SBC in it )

Thanks,

Jim

[ITSNOTAGN]

anything you can find from a 67-gtq and up will work just fine. That turbo, or a 70gtq or gts would be absolutely perfect for a nice weekend cruiser, and wouldnt require a big stall. Anything from 2400-3000 would be nice and controllable, and would still hit pretty hard. With the gtq you would be looking at around 26-2800 for a good 10psi, gts would be in the 28-3000 for 10psi. Otherwise, i would really like to see a Borg Warner S374 on there. It has been proven to do 700+whp on a stock LS2, and spools about as fast as a 70-small 76mm turbo. Also the wide compressor map would really boost that midrange tq output. At any rate im assuming your not building a wild track car, and i wouldnt doubt seeing 550ft-lbs out of that setup, with close to 500-525whp, on pump gas and about 12psi.
My vote, 70mm gts or a BW S374, with the BW for bigger power, the 70mm for cheaper, cruising.
Gary

[Louie L.]

Coil on plug will not ever work with a 6AL box. I also do not see how you can make COP work on a carb motor. Maybe if you could use one of those MSD boxes made for a carburated LS1. There will be quite a bit of research needed to pull that off.

[SRGN]

I'll let you know what works, I already have the mockup and one header done GN accessories, turbo bracket, turbo flange. I'm installing a GN drivetrain right now to get the chassis and electronics sorted out for when I get the 350 SBB done. I have a TE45A I was going to try, looks like a close match for airflow with stockish heads.

[ITSNOTAGN]

oh yeah, if your using a 3-bolt flange, and have a te45, i would use it. that will take you to some power, and just upgrade to a 70mm or so later.
Gary

[87natl]

I love that you are doing this with a SBB, keep us updated, and good luck!

[gs_jimmy]

Thanks for all the input. I may need to scale back a little. Serp system stays, most likely need to reuse the HEI set-up to get this back on the street.

Still working out the pass side exaust. Drivers side is the original manifold, will route under the block (stock Y pipe style) then mate into the pass side like a TR. Still need the turbo mount bracket to figure out how to make the header set up. Anyone got an old crusty BUICK 350 header?

Jim

[SRGN]

Jim, I bought flanges from Mark Burton(Justa350) over on V8Buick. Very nice pieces, were around a hundred bucks. The port locations on the SBB are close to SBC, you can buy a pair of cheap chevy turbo headers on ebay and be halfway there. That's what I used for the driver's side, pass side is being fabbed up over the next couple months as time allows. I had a junk passenger header for a GN I hacked up for the turbo flange, it'll be a log and I'm using the SBC header crossover. Most distributors won't clear the serp belt bracketry without major surgery unless you use the champion A/C delete bracket. I will be using a stock GN cam sensor for cam signal, and I'm trying to find a crank trigger that works easily. I have a TA intake that's getting injector bungs welded in. Will be using a BS3 for management.

[gs_jimmy]

SRGN


I looked at the BS system also. Do you think it is possible (practical) to go to the trouble of creating a '87 SFI setup using sheet aluminum for the SBB? Could use a junk manifold to get the front end of the manifold then build out the rear to insure the correct sized plentium area.

This will allow for a mass air unit in the stock location along with direct port injection.

The other simpler option would be a 90* mass airflow elbow and the use of a modified 4bbl T/A manifold. Then match the intercooler piping to the new Mass Airflow inlet. I'd imagine that the serp system clearance will be fine.

As for a distributor, would the stock small cap points unit work (pertronix upgrade) or should I try to use the cam sensor/crank sensor set up? Will the BS3 system allow for the computor management of the engine?

[SRGN]

Originally Posted by gs_jimmy

SRGN


I looked at the BS system also. Do you think it is possible (practical) to go to the trouble of creating a '87 SFI setup using sheet aluminum for the SBB? Could use a junk manifold to get the front end of the manifold then build out the rear to insure the correct sized plentium area.

For the time you'll spend making it work, then attempting to equalize airflow, it's not the most practical option.

Originally Posted by GS Jimmy

This will allow for a mass air unit in the stock location along with direct port injection.

Your next idea covers this. Putting a mass air anywhere upstream of the turbo will work, but I'm biased towards speed density for the ease of tuning.

Originally Posted by GS Jimmy

The other simpler option would be a 90* mass airflow elbow and the use of a modified 4bbl T/A manifold. Then match the intercooler piping to the new Mass Airflow inlet. I'd imagine that the serp system clearance will be fine.

This is what I'm using. The elbows that bolts to the 4bbl flange are readily available, and I'm going to weld injector bungs into my TA intake.

Originally Posted by GS Jimmy

As for a distributor, would the stock small cap points unit work (pertronix upgrade) or should I try to use the cam sensor/crank sensor set up? Will the BS3 system allow for the computor management of the engine?

The BS3 will control CNP or distributor ignitions. I haven't had a chance to try my small cap Mallory distributor to see if it clears the belt tensioner, if you're thinking about using a distributor I can try it on my mockup engine in the next couple weeks. I may have a trigger wheel for my stock 350 balancer made, just haven't had time to sit down and draw it up on autocad yet(newborn babies take up a lot more time than I originally thought). I think efi with cam/crank sensors is the way to go for me, to get going on the project a blow through carb with distributor will take up a lot less time. I was originally going to try the blow through, but I have to do everything the hard way

[gs_jimmy]

Art,

The points style small cap does not clear. So, I'm back to the cam sensor/crank sensor & running distribtorless. That brings in the Ford EDIS coil on plug (see V8Buick forum). Since we already know that the cam sensor is going to work (based on the signal) I think we're halfway there.

Still need an aluminum manifold for my 350 Buick, a little grungy is Ok since it has to be converted to SFI. I did like your idea on the Big Shot system, would take the guesswork out of the fuel delivery.

How are you mounting the computer system? Thinking that it could be placed behind the glove box door for access.

Last dumb question, regarding the SBB block, if the HP level is kept reasonable (500-600) are you seeing a need for a girdle and or hard block? I realize if I push too hard I could see some movement in the mains. I'll be using the high nickel '69 block (after I kill a '78 production motor).

Thanks,

Jim
'69 GS California