I have been doign alot of research on the L03 and TBI and so far I haven't seen a single bolt on supercharger or turbocharger for the TBI. Can anyone clarify this for me.

 

To my knowlege, there are no turbos. There have been a few people on these boards to supercharge their TBI's and some have had very good results IIRC. Do i search its come up a few times. If you're looking for that extra jolt to beat the GT's out there it seems that most people have the best luck with a shot of NOS, and its much more cost effictive too. (always a plus)

 

There is a whipple TBI supercharger out there can be used on TBI set-ups but it is expensive and yields only small gains. The money that you put into such a set-up can be spent on another motor that will make more power than your bossted TBI. If you want some boost just add a small shot of giggle juice.

 

Paxton used to make one, there was a guy on here a while ago that had it and I think he was going 14.10. I bet you could take that vortech carb bonnet and covert it to accept a tbi though if you really wanted to.

 

There was somebody on here, I wanna say within the last month, thta posted his supercharged tbi, and he was running pretty good IIRC. Somewhere in the 12s I think. Like the guys suggested, try a search and you will find it.

 

Holley/Weiand makes a roots style for the trucks, it should bolt in ok. but you will need a 3" cowl.

you can also use the universal short nose version, and space the pulley's correctly, along with an adaptor plate.

you can also use a cent. supercharger, and a carb hat.

the problem with all of these option, is getting it fuelled properly, you will need a new fuel pump, and a FMU at mininum.

 

when i had my tbi car dynoe'd this summer, I asked the guy at the shop what he thought of supercharging a tbi, he said they tried doing a 350 truck and it didn't work out at all.

Just my input.

Ty

 

did you ask the important questions? before you toss out an idea because it didn't work for someone else, you need to know what caused it to not work.

how did they boost reference the fuel delivery? how did they modify the timing curve, since alot of roots blowers like lots of initial timing, and then either a flat timing or reverse curve. what didn't work well? WOT not all that? part throttle driving was good? it wouldn't idle?

i really think that a roots blower with TBI, if you execute it right, would work very well.

 

I think a nice setup would be a roots blower with a tbi sitting on top with an adapter plate. That's one way to end the best manifold debate, lol. I myself am going the nitrous route. The way these cars respond to nitrous is rediculous. I believe if you have the right setup a 100-125 hp shot can yeild you a drop of over 2 seconds. It's just crazy how much they cravy N2O.

 

personally dewey, i forget the details. but i figured i'd throw it out because these guys are very capable. I think it was a vortec style supercharger tho.

TP

 

Granted the Paxton kit that I have on my car is no longer available you could easily adapt a kit for the TBI truck and make it work. I originally paid $2,400 for my super charger kit back in 1995. The car was running low 13's on the street (down from high 16's) when I pulled it off of the street and went full race.

Question that always comes up is; could you put a blower on a later model 350 and make better power? Sure you could, but at the time that I purchased my car I paid 12.5K brand new (still have the original sticker) and to get a Z28 would have cost at minimum an additional 5k.

The current motor has 95k miles and has had a supercharger installed since 1995. It does not leak a drop of oil or smoke at all.
In the interest of going faster I do plan on replacing the LO3 with a new GM Goodwrench 330hp 350 and using my intake, blower and TBI combo to make 500 hp to get me into the low 11's.

I will miss however letting the car that I just beat know that they just lost to a 305! The look on peoples faces is worth the price of admission.

MD

 

Here is a picture of my set up.

MD

 

how did you get the extra fuel into the motor?

 

Racer, what fuel pump are you running?

the reason i tend to like the roots route with TBI, has to do with the location of the injectors, with a carb hat and a cent. SC'er, you have to raise the fuel pressure 1:1 for every pound of boost, you also have to raise it even more to make up for the lack of the factory computers ability to see more the atmospheric pressure. so if you are running 12# of boost, with 12# of FP stock, you will end up probably running something like 30# of fuel pressure under full boost. (granted the injectors really only see's the stock fuel pressure + whatever you add via a FMU)

with a roots blower however, since the injectors are not seeing any of that pressurized air, you don't need to run the extra fuel pressure to over come the air pressure.

just something to think about. both ways have their ups and downs, just like everything.

 

The supercharger kit came with an FMU unit that raises fuel pressure as the boost rises. I am running 25 psi of fuel pressure at idle.

The fuel pump I am using came with the kit too. I am not sure what kind it is.

MD

 

Racer, you won't be able to swap the intake over to the 330HO engine. Unless your 305 is running Vortec heads.

Steve

 

The other issue witht he carb hat is the throttle body itself. You have injector pods in the way, etc which are being blown on pretty hard. If you wanna go that route, get a big monoblade TB and run mpfi, or mount large injectors elsewhere on the manifold.

I had considered doing some stuff with the stock TBI throttle body, but its just a bad design..

The roots blowe as mentioned above, will prolly work great. Just run a FMU & BTM.

-- Joe

 

Hey racer, just stupid question, but since we are on a topic that is a bit out there anyway (cost of a blower kit some were in the 2k+ while a decent set of heads can be had for around 600-700 new), but what kind of gas mileage did you get before you went full race? I know it is a silly question, but i am curious.

 

The fuel mileage was about the same as long as I did not punch it at every light. Blower makes most of the boost in the higher RPM range.

About the first part of your post, are you implying that by simply changing the heads on a L03 it would get you in the mid 13's? I was running mid 13's with the blower with stock heads and cam and the installation of the blower was no where near as involved as changing heads would have been. My main goal all along has been to only install parts that would be able to be used on a bigger motor down the road.

MD

 

No, but i was implying that there are cheaper ways to get the motor to run quicker, although they may not be easier. I would normally think that forced induction would be after basics like heads, cam, gears, suspension, exaust, ect to get the most out of the supercharger.

 

Jokerman,

You are correct if you plan on keeping the current engine. My goal has always been to get the most from the LO3 without actually "getting into" the motor. I used the money that I would have spent on heads and cam to set up the suspension, rearend, transmission and exhaust to handle the power of a bigger engine.

It all comes down to what your final goal is, but most importantly is to set up a plan in the beginning so that you do not waste money on parts that will not ultimatly contribute to your final goal.

MD

 

Good call Racer

I was told to do the same. Get a 350 and build it up and just leave the 305 in the T/A until I am ready to drop the new built engine in the bay. I plan on doing either that or saving up enough money for a pre-suped crate 350. I figure that would be my best bet instead of dumping a whackload of cash into a motor that has been driven by 4 other people.

 

Racer3313,
What kind of specs are looking at for your next engine, and do you plan on keeping the 2bbl tbi? I am just curious because I have been looking into either supercharging mine or going with a commander 950 system. Anything to get more air. The supercharger would yield more gains obviously, but I'm not too sure how well it would work with my setup and stock ecm/map sensor.

 

Racer, I too would like to know your set up.

I like the idea of keeping the original motor since my car is in such good shape. A numbers matching 305 that is running 13's or lower is my idea of a damn good time.

When you bolted yours on, is that all you put on, was the stuff from the kit? All internals were kept stock?

Another question, did you have any clearance problems, because if possible I want to keep the stock hood.

 

ThraxXx,

I have a 91 Firebird Formula 305TBI with a Paxton SN-92 (and modified impeller) that I installed in 1992. On street tires it runs the 1/4 in 13.82 @ 103, 60ft in 1.97, 0-60 in 5.43 with 328hp and 355lb.ft of torque. It's a delight to just sit behind the wheel.

Don Moore

Here are the mods -

1991 Pontiac Firebird Formula 305 TBI
Purchased 7-16-90.
54396 original miles (10-15-03).
Synthetic oils and grease.

Modifications

Edelbrock TBI Performer intake.
TBI modified by Turbo City to flow 565 CFM.
TBI bonnet 1-inch spacer.
Auto Meter air/fuel ratio monitor.
Crane roller tip/needle bearing fulcrum Gold Race Rockers.
SLP cam - Dur. @ 0.050 0.209/0.214, Lift 0.471/0.490, 112° CL.
K&N fender mounted air filter.
SLP Tri-Y 1 5/8th-inch headers MCCI coated inside and out.
Flowmaster two chamber cross flow muffler.
Custom 3” Cat-Back exhaust system.
Random Technology 3-inch catalytic converter.
Auburn posi.
Richmond 4.10 gears.
TA Performance Products rear end cover.
Dacco 3000 flash stall torque converter.
Hayden transmission oil cooler.
Darrel Young 700R4 TV Valve 0.521.
Fairbanks 2-4 Billet Servo (700R4)
B&M megashifter.
Paxton supercharger (modified for 6.5psi boost).
Adjustable vacuum controlled fuel pressure regulator-external to TBI.
Corvette fuel pump-inside tank.
Vacuum-Boost & Fuel Pressure gauges-mounted inside car (isolator mounted on firewall).
ADS custom chip (primary), Hypertech Thermomaster (secondary).
160° thermostat.
MSD 6AL ignition.
MSD Blaster 2 coil
MSD tach adapter.
MSD adjustable timing control.
MSD Pro-Billet Distributor.
Bosch platinum plugs.
Accel 8mm spark plug wires.
Trunk mounted battery.
BF Goodrich Radial T/A 265/50 HR15 Front.
BF Goodrich Radial T/A 275/60 SR15 Rear.
Crager Drag Star polished aluminum wheels, 15x8.
Monroe adjustable air shocks, rear.
South Side Machine weld on Sub Frame Connectors.
Cloyes double true roller timing chain set.
Cyberdyne speedometer calibration box.
Mildly tinted windows.
Repainted stock Bright Red w/BASF basecoat-clearcoat 5/2003.

 

When I originally bolted on the supercharger all I did was the kit. As I have stated earlier the motor is stock below the intake.

I believe the stock hood would fit unless you did a spacer on the TBI.

MD

 

I am hoping to get a mild 350 and keep my injection and blower intact. I just want a 350 that is rated at 300 hp or more.

MD