Car: 1990 305 TBI w/700R4

What is the most (crank) horsepower the stock tuned computer can handle with bolt-ons? And how would it behave with a new intake manifold and or exhaust manifold?

 

Its not that simple. Since TBI is a MAP based wet flow system I'd say a new intake would throw it off quite a bit depending on how different the intake is from the one the ECM is set up for. Exhaust changes would have less affect on the tune.

 

honestly. the max it can support stock is basically stock.

now i ran my 350 with a 305 computer for a few years and i didnt have any problems. but i had 350 injectors in it. it may have run lean but i could take it to 5500 rpms..

i went with a 350 caprice computer and didnt feel any difference

i went with a 305 performance chip on the 305 computer and it felt better.

if you went with the peformer tbi intake and some headers you would not need chip work. but chip work would benefit the car anyway.

you can buy the ebl and do some VE learns and get better power and more fuel economy too.

 

So I should focus on doing a full exhaust headers back and leave the intake manifold alone? I have an open element air filter currently but was considering a new intake manifold.

How much does it cost to get my ECM tuned? I've heard it's bloody expensive! I was hoping to avoid spending the extra $ since I'm sort of on a budget.

 

You could do exhaust and still probably be ok on the stock tune. Exhaust alone wont get you too much though power wise. I will mention that I went from a bored out stock TBI manifold to a Weiand Speed Warrior dual plane and my tune was way off. I basically had to start over.

I've never heard of anyone offering tuning for our cars beside mail order places like tbichips. If you are willing to put in the effort you can tune the ECM yourself for a few hundred dollars in prom burning equipment. For a while I was doing this and honestly it works pretty well. Another option is the EBL system mentioned by UnderCover which I now use, but that is a little more expensive. EBL does have a ton of features and is way better than swapping proms though.

 

if your on a budget keep that stock 305 tbi all stock and reap the rewards of pretty good gas mileage and just drive drive drive!

but these cars benefit from having the exhaust upgraded tremendously.

 

What sort of gains goes one get with that TBI performer intake?

How much gains are we talking? I'm not really after high horsepower, just enough to get me as close to 6 seconds or under to 60 mph as possible.

 

I am pretty sure there is an old thread here where someone mentioned dyno results before and after the TBI performer intake. I believe everything about the car was stock with the only mod being that intake. The difference was just a few horsepower. Hardly worth the effort IMO. I don't think you are going to get to your goal with just exhaust.

 

Well at least the intake manifold and full exhaust will make it sound better along with a reasonable performance increase. I plan on doing pullies, plugs, wires, ignition, and a better open element filter+intake as well. What else could I do while under a budget?

Sucks that all my money will go to paint and bodywork. But, at least it will look good.

 

really as long as it looks good and sounds good screw the performance part of it.

I wouldnt bother with the intake either.

just put some sort of modified air cleaner on it. headers, full exhaust. do the ultimate tbi mods. and call it good.

 

Someone will say it sooner or later. save your $$$ for now maybe invest in gold and buy a 350 crate engine and begin the journey later. You will be happy you did.

 

Stock ECM can handle more power than most on here would lead you to believe. You just need a healthy fuel system to do it. The stock pumps are notouriously weak and most stock regulators do not even deliver the specified 11 PSI of fuel pressure. I would suggest a TPI pump and adjustable fuel pressure regulator at a minimum. At the very minimum the stock ECM can handle headers, a full exhaust, ported stock throttle body, cold air intake setup, and 1.6:1 full roller rockers.

As for making your car perform, concentrate on the basics first. No sense on trying to make power if you can't put what you have to the road.

Lower Control Arm Relocation kit
Locking Differential
GEARS

After that, I would beef up the transmission

Transgo Shift Kit
Corvette Servo
1996 4.3 S10 Torque converter
Largest aftermarket transmission cooler you can in series with the stock in-radiator cooler. Plumb it in after the stock cooler on the return side line. Let the hot fluid hit the radiator first to cool it down then on to the extra cooler

Get your engine into the best state of tune you can before attempting bolt-ons.

AC Delco Plugs
Quality set of low resistance wires
Quality Distributor cap
Quality Rotor
New Fuel Filter
New PCV Valve
Change all the fluids
170*F thermostat
Low Temp Cooling fan switch

From there I would do the following.

TPI Fuel Pump & Adjustable regulator
Ultimate TBI moded TBI
Flowmatched Injectors
1.6:1 self aligning full roller rockers
SLP Tri-Y headers are my personal preference, but haven't been made in years
Full exhaust from the headers out, I would run 2.5" off headers, into a flowmaster Y and high flow 3" cat and single 3" straight through muffler. Forget that crossflow crap if you want power.

I also gained about 15 RWHP @ 5,000 rpm using a 3 way adjustable timing set, retarding the factory cam 4* with no sacrifice of torque or driveability.

 

I agree. Looking good is definitely high on my list but sound is higher. It did sounded good before the engine went.

I'm sticking with the 305, other than minor bolt-ons I would like to keep it as original as possible. I can always revert the exhaust and intake back to stock if need be.


Wow, that's some good info there thank you. I will archive that in my project file.

 

2.73s with what your running = crap off the line. Its not cheep but 3.42s with posi./LSD will give you best bang for your buck.

 

I know 2.73 gears aren't good for acceleration but it came on the car originally so I gotta keep it. Plus you're right about it's not cheap! I need that money for paint and body.

 

One can find a 3.42 geared rear end from a plethora of V6 cars in this area. Gears make a great bang for the buck mod. You would be surprised how many V6 cars came with a 3.42 posi and how many V8 cars had 2.73 open differentials, stupid idea GM.

 

3.42's don't help with fuel economy though

 

Having regeared multiple vehicles, I disagree. Lower gears help fuel economy the 95% of the time you aren't doing 90 mph down the highway.