GMC Truck Forum banner

1 - 13 of 13 Posts

·
HAPPY NEW YEAR
Joined
·
3,599 Posts
Discussion Starter #1
Alright guys I have a few questions about my 1995 straight 350 TBI/ 5.7 L. First of all, we all know its a slow mother. Will my TBI have more HP than say a 94 or under? A friend also told me, that in the long run, I can squeeze more horsepower out of my engine, than a vortech?

Also, what is the difference between my engine and a vortech? I really am new to engines and I love watching the way they work! If you can elaborate on the differences, that would be great.

Lastly, whats a "classic" hp/torque mod for my engine? Im only 16, not really interested in the superchargers, etc. Maybe something like headers? I really dont know just throw your ideas out there! Thanks again for any replies!

griffin
 

·
thats right
Joined
·
1,399 Posts
ok your friends are just flat dumb. they dont know what the hell they are talking about.

NO you cannot get more power out of a TBI than a vortec. and no your truck's motor is identicle to the 93 and 94 models. the 88-93.5's were SLIGHTLY different and had 5-10 more HP.

the differences......um you need to look at all kinds of motors and just imagine whats going on. with a carb, fuel and air are mixed in a bowl then dumped into the intake. with a TBI the same is happening, except now the fuel is sprayed into the top of the intake to mix with the air as it goes to the cylinders.

the vortec uses multiport injection injecting fuel at each cylinder right next to the valve. this type of injection has the most capability of making power. its most efficient.

the vortec motors get their name from their heads. the vortec heads help add about 20-30 hp, the multiport added the other 25. the heads on a TBI are boat anchors at best as most engine buffs would describe them. i dont know alot about how the vortec heads do it, but i think they mix the air and fuel in a special way.

yeah you could do some motor mods like headers, catback exhaust, pulleys. but in order to really add some power you need new heads, a cam, and some custom tuning. IMO its flat out a waste of money to mod a TBI that much. they just suck honestly. they are great, reliable truck motors. i miss mine because it was so simple. they make good lowend power where you need it, but they cannot make high end power. hell they redline at 4800 rpm. these new LS1 based 5.3s make their peak torque at 4800 and pull through 6000........if i were you i would leave the motor stock and appreciate the simplicty and reliabilty. believe me you will be pissed at yourself from wasting money on something trying to make it what it can't be later on.
 

·
Registered
Joined
·
1,816 Posts
The thing about the vortec heads is that they flow alot better, and the fuel is not mixed with the air until its practically in the cylinder, making it more efficient and powerful. With a TBI its mixed at the top of the engine, and goes thru all kinds of twists and turns that muck it up and prevent good atomization of the fuel, hurting power and efficiency.

I do'nt have any money, or i'd probably put some money into mine, namely new intake manifold, heads, cam and long tube headers, the stock parts are junk. And doing that would mean custom tuning the computer, which is also a fair amount of work. Someday.... I think and have heard of it being possible to get 350hp out of a TBI, BUT that requires alot of work and $$, but I think it would be fun to do.

I think they made 210 hp 300 tq up to '94, then for 95 it went to 200 hp 310 tq, but i'm not totally positive about that. The lack of power above 4500 rpm is because of the heads, intake manifold and TBI unit (glorified 2 barrel carbuerator), they simply don't flow enough.

Other than their lack of power and gas mileage...they're great. Very reliable, they last just about forever if you take care of them (159k and counting on my 350, 300,000+ on my dads 454), and they're really easy to fix when they do break (how many car computers do you know that you can read the trouble codes with a paper clip?)

I see you've got straight pipes listed in your sig, what exactly do you have? If you don't have enough backpressure, as in no mufflers and cats, then you're going to kill your low end power.
 

·
Registered
Joined
·
1,895 Posts
Jeff said:
....IMO its flat out a waste of money to mod a TBI that much. they just suck honestly. they are great, reliable truck motors. i miss mine because it was so simple. they make good lowend power where you need it, but they cannot make high end power. hell they redline at 4800 rpm. these new LS1 based 5.3s make their peak torque at 4800 and pull through 6000........if i were you i would leave the motor stock and appreciate the simplicty and reliabilty. believe me you will be pissed at yourself from wasting money on something trying to make it what it can't be later on.
Jeff...Did you even have any mods on your old truck? I didn't think you did, so I'm curious what you're basing all of your information off of? You always preach that the TBI's are easy to work on, but what have you actually done to one? :think:

Redline at 4800? The absolute redline is 4500, but they shift at 4200. If you saw 4800 in yours, your valves were not happy.

I would much rather have my peak torque down low where it is useable during everyday driving. How much time do you spend cruising at 4800?



Griffin...It is people like this that inspired me to mod my TBI. Most people talk down on it because they throw money at it, without knowing what to do. Then they complain that they wasted all of their money, and it can't get out of its own way. I have "wasted" some money on mine, and it's much better than it once was.

Judging by your age, I'm guessing that you don't have alot of money to put into it. If you don't want to tear into the motor, the TBI's respond very well to simple bolt-ons. Depending on your budget, I can offer a few suggestions.
The frst things i would suggest are....
160* thermostat ($6)
14"x4" open element air cleaner ($40)
2.25" dual exhaust ($150)
CATCO catalytic convertor ($60)
Magnaflow or Dynomax muffler ($60)
Hooker Competition Series headers ($320)

After increasing the airflow, both on the intake and exhaust sides, you need more fuel to take full advantage of it. You can make your stock fuel pressure regulator adjustable in under 30 minutes, or you can buy an aftermarket unit for $70. At this time, I would also get a TBI spacer ($60) and injector pod spacer ($20). March Power pullies helped me out too. You can find them for about $50.

Now, you're ready to get into the motor. The stock intake manifold flows very poorly over 3500rpms, but it is matched to the weak factory cam, which dies out at 4200, not 4800, like Jeff previously stated. 600rpms may not sound like much of a difference, but you're approaching valve float at those numbers. Edelbrock makes a replacement intake #3704, that will cure the poor flow of the stock piece. It sells for $200. Since you have the intake off, you might as well swap the cam. The Crane 2030 would be a nice improvement over the tiny stock cam.

Somewhere in the middle of all that, I would work on the tranny and rear end. At a bare minimum, get a TransGo shift kit. You would also benefit from a higher stall convertor, but this would depend on your rear end gear ratio. You probably have a 3.42, which is great for highway driving, but if performance is your goal, you need at least a 4.10.

These are just the basics. There are several things you can do to get more power out of your TBI. It just comes down to picking the right parts, and turning some screws.
 

·
HAPPY NEW YEAR
Joined
·
3,599 Posts
Discussion Starter #5
thanks 91_bowtie for the extensive and educational post!

Despite being shot down about the TBI, I am still very interested in modding the motor, but one of my questions is, will aftermarket HP mods decrease the reliability of the engine?
Example: Making changes to the computer for the benefit of hp, etc.

I see you've got straight pipes listed in your sig, what exactly do you have?
Ok, I don't know much about exhaust, this is what I have been told I have: It is one thick pipe straight from the engine, no muffler, but just a cadalytic converter, it then branches off into two pipes, I believe to be 2.25" into duals. (Y-pipe) It has a low growly grumble to it, but I would like for it to get alot louder and pop! I am about to get a mod for the exhaust. I buy this motor that is installed right after the cadalytic converter and you flip a switch inside your truck and it makes to pipes like open headers (loud as [email protected])

Also, one last question is, I would like to basically get my engines HP/Torque up to the level of a stock vortech. Knowing this, how much horsepower/torque is my engine putting out (95 350 tbi 5.7) vs. the stock vortech 350 5.7? Thanks again guys for any help!

griffin
 

·
Registered
Joined
·
1,816 Posts
Your exhaust sounds fine to me, the cat should make enough backpressure to keep your engine happy.

well, the vortec 5.7 makes 255hp and 325 tq stock, and you're making 200ish hp and 310ish tq if your engine is running correctly, maybe a bit more with the exhaust. I don't know where to go from there :)
 

·
Registered
Joined
·
658 Posts
damn this shit makes me want to dump hella money into my old 1992 TBI just to prove people who talk bad about them wrong....
 

·
Registered
Joined
·
1,895 Posts
Southern Pride said:
thanks 91_bowtie for the extensive and educational post!

Despite being shot down about the TBI, I am still very interested in modding the motor, but one of my questions is, will aftermarket HP mods decrease the reliability of the engine?
Example: Making changes to the computer for the benefit of hp, etc.


Ok, I don't know much about exhaust, this is what I have been told I have: It is one thick pipe straight from the engine, no muffler, but just a cadalytic converter, it then branches off into two pipes, I believe to be 2.25" into duals. (Y-pipe) It has a low growly grumble to it, but I would like for it to get alot louder and pop! I am about to get a mod for the exhaust. I buy this motor that is installed right after the cadalytic converter and you flip a switch inside your truck and it makes to pipes like open headers (loud as [email protected])

Also, one last question is, I would like to basically get my engines HP/Torque up to the level of a stock vortech. Knowing this, how much horsepower/torque is my engine putting out (95 350 tbi 5.7) vs. the stock vortech 350 5.7? Thanks again guys for any help!

griffin


No problem man. That's why I'm here.

No. If anything, the reliablility would become better, as long as the computer is aware of the changes you make.

The exhaust you have now sounds good. You should know that when you open up the cut-out, your low end torque will disappear. If you want it to be loud, put it in front of the convertor. If it's placed after the cat, it won't be nearly as loud.

Those 285 tires are what's killing you. Check the RPO list in your glovebox to find out which gears you have.

GU4=3.08
GU5=3.23
GT7=3.33
GU6=3.42
GT4=3.73
GT5=4.10

Being a Z-71, I bet it's probably the 3.73. If you want the easiest way to ourun a vortec, then to start off, you need to get new gears. With that tall tire, you should be running 4.56's. If you swap the gears, and get all the bolt-ons (headers, spacers, etc) you should be able to outrun a stock vortec. Check out www.turbocity.com and www.cfm-tech.com They have alot of good TBI info.
 

·
Registered
Joined
·
1,895 Posts
Joshs2002Silverado said:
damn this shit makes me want to dump hella money into my old 1992 TBI just to prove people who talk bad about them wrong....
hella money? :LOL:

:think: I never said that was the only reason. I did it because I wanted to, and I knew it could be done. Talking to people who lack mechanical knowledge is just part of the reward. :grin:
 

·
thats right
Joined
·
1,399 Posts
Joshs2002Silverado said:
damn this shit makes me want to dump hella money into my old 1992 TBI just to prove people who talk bad about them wrong....
that was exactly my point. If you know how to do all the work yourself, that helps the cost dramatically. but to each his own. im just sharing what i learned from my experiences. the lesson for me was: picture what you REALLY want in a truck, and save for that without settling for anything less. i wanted a newer truck and im glad i went for it before putting alot more into the 94. good luck with your choice. if you are happy that is ALL that matters

for the record my 94 had 3 bolt on mods. lol headers, catback, and intake :anitoof:
 

·
Registered
Joined
·
658 Posts
Jeff said:
that was exactly my point. If you know how to do all the work yourself, that helps the cost dramatically. but to each his own. im just sharing what i learned from my experiences. the lesson for me was: picture what you REALLY want in a truck, and save for that without settling for anything less. i wanted a newer truck and im glad i went for it before putting alot more into the 94. good luck with your choice. if you are happy that is ALL that matters

for the record my 94 had 3 bolt on mods. lol headers, catback, and intake :anitoof:

yeah well i already have a 2002 and because of warranty issues and my dad i dont want to fuck with it right now....so i think im going to start working on my 92....just have some fun....love that truck
 
1 - 13 of 13 Posts
Top