what cheap upgrades should i do to achieve 300hp and approx 350lbfttq to my lo3? be specific on sizes/dimensions. thanks alot

 

Man i hate to be the bearer of bad news, but the heads and tbi injection on that cubic inch motor will severly limit you, just spray the snot out of it and be done with it.

 

actually instead of asking what i need to do inorder to achieve a certain hp/tq why dont you tell me upgrades and let me know what each one does alone. that way i can determine what is necessary. thanks

 

Allright, i believe you have 170 hp, and 210 ftlbs, say edelbrock intake-10 hp, holly throttle body-10, hedders-15, full exhaust-10, chip-10, k&n air filter-5, underdrive pully kit-10, all of this is a modest given hp gain, you would be lucky to see about 260 flywheel hp, your torque might bump to 275, but once again this is being generous, the heads on your car are a sworl port desighn, verry low quality for hp production, and the tbi induction is not a winner for making hp, it is nearly impossible to tune the computer for a decent cam upgrade, but if you opted for say vortech heads and a holly tbi system you could gain worlds of power and meet your desire quite easily, i hope these details help.

 

thanks alot

 

come to think of it, i carburated a tbi 305 in a 90 i had, i used a edelbrock intake, holly carb, 214 @ .050 cam with .440 lift, hedman hedders, hedman y pipe, fill 3 inch i pipe with 2 1/2 outlet flowmaster, it still wasnt that great over the stock tbi because of the heads and the lack of a stall converter and gears.

 

buy a new engine

 

Use the stock L03 as a boat anchor for your raft as you sail to the crate engine depot.

Now that thats out,, STICKIES!!!!!

 

it is a fun engine if you dont want to go fast, thats why i got rid of mine

 

I have seen people spend quite a bit on these cars and still not get into the 14s that being said the l03 is a great motor to learn on but not one to go fast.

 

i have considered swapping the engine but with what, from where? how difficult are these swaps gonna be? im not too mechanically inclined,but my dad knows a thing or two. any imput is greatly appreciated. lets set the budget at approx $2000 for something near turn-key. with atleast 260hp/320 tq. oh yeah i would like it to work with my 700r4 trans.

 

I hate to be the bearer of bad news, but you are WRONG, the heads and the TBI are NOT limiting his engine at this point.

It is the exhaust from the head ports back and the weany cam.

 

Hey fast355, have you ever used the World SR tourqer heads????? Thanks, Tom

 

To the original poster of this thread please ignore every single post up untill Fast355's post.

The stock ecm is completely tunable for any cam you would want to run, and with the addtion of the EBL you could run any cam made.

You can't add HP from single parts.

The stock TB and heads can support just over 300 hp, Fast has done it.

Start with the stickies, then read......alot

 

Have you guys ever ported heads? If you have ever seen the poor design of a tbi head compared to an earlier head or a tpi head it is a world of difference, you are better off getting a set of junk yard heads, or even a machine shop will have a set of better heads laying around, it is not cost effective to use the tbi heads, sorry but it is the truth.

 

I have not run them. I know several people who have though. They are not any better than stock carb/ TPI heads with 1.94/1.60" valves.

I however DO recomeend the latest ZZ4 aluminum castings. GM has really gone through the paces and these seem to be about maxed out straight from the box. With a little clean up work using sanding rolls, I saw flows of 240+ CFM on the intake side and 180 on the exhaust.
----------

I HAVE ported them and HAVE even ported the SWIRL PORTS.

Most of the flow is still there in the swirl ports. It just enters from the side.

There is not a SINGLE GM head that I would run IF I were worried about Track times only. I would without a doubt run an aftermarket casting.

I put 240 to the wheels with a stock cammed, stock swirl port headed, stock 8.75:1 compression 350 TBI engine. With the factory sized TBI unit and STOCK intake manifold.

 

Pretty much all the earlier heads blew chunks without porting. The LO3 heads are definatly bad, but the TPI heads arnt much better. Poor flow and the chambers suck on pretty much any early SBC head.

Now, world of difference is something like the vortecs, or the higher end aftermarket heads. The difference is immediatly noticable. Raised runner that gives a nice, clean shot at the intake valve, tight chamber, spark plug moved toward the center rather then way off to the side. Heads like that you dont even have to bolt them on to know its going to make more power. Easy to see, right out of the box.

At this point, though, there is a lot that can be done that will really boost the power without having to dig into the motor. Cam, intake, exhaust, tuning, etc. Even junk heads can still make some power on a proper setup. If he where to swap heads, and injection system for that matter, there probably wouldnt be much gains with everything else constant.

 

Thanks fast355, I didnt realize the TPI heads were better than what I have now..I have not done alot of reading on 305 heads..Will do so, and try to sort this out..For now im not at the point where I need heads, but was just curious. To the original poster good luck, and have fun.Tom

 

The TPI heads aren't really that much better than your TBI heads. In some aspects they are worse.

 

Ever notice how people come in with post counts under 500 and flame L03 TBIs?

TBI has more potential then TPI hands down and has been proven many times.

People who make power with TPI engine no longer run TPI they run systems like the HSR tunnel ram or are FI.

Just read the stickies to start off.

 

Definately agree there. Hell my little brothers Astro work van with 200,000 miles on its LB4 4.3 TBI, tired valve springs, dying original fuel pump, pulling around 1,000 lbs of tools in it will do nearly 100 MPH.

https://www.thirdgen.org/forums/atta...m-wot-dash.jpg

 

I dont have alot of post, but I am impressed with my TBI so far..I just have to learn the fine art of chip burning.....

 

just noticed one of the 1st posts on this thread its 170 hp and 255 ft/lb not 210 ft/lbs

 

1993-1995 Truck/Van 305 TBI engines are 180HP/275 TQ

 

but that is due to much better exhaust but lacks the roller valve train

 

The trucks do have a slightly better flowing exhaust that is 3". They DO have Roller cams in the 1992-1995 G-series atleast. I have had 3 of them so far and seen MANY more. 4.3/ 305 and 350. My uncles stock 1994 C1500 350 TBI was a factory roller cam engine as well. They all have the peanut roller grind cam though.

 

what order would you do the upgrades in? list brands, and other specs you reccomend. remember getting an lo3 to the 260-300hp/300-350tq range while still being able to use stock 700r4 trans. thanks alot

 

well 1st off get an open element air cleaner from summit and remove the rear hood seal also get a new breather with it then your car can take in as much air as it could ever need

you should do a full exhaust
headers to high flow cat "or cats" to free flowing catback with tbi's it tends to add a decent amount on its own being how poor the stock tbi exhuast is

you can remove the ac and smog pump and lose weight and free up some rotating mass

you could try a cam like lt-1 or zz-4 cam
some 1.6 rr or even just try the roller rockers on the stock cam to get some more out of it

or get an aftermarket carb/tbi manifold

also you can tune the stock computer for better proformance ive seen gains of 15 hp and 20 ft/lbs alone with just tuneing these cars are setup for gas saveing and smog not proformance

remember hp isnt everything

from there id say go with better rear end gears i put 3.23s in mine and the car really woke up most people go with 3.42 or 3.73s but i wanted decent take off but needed to be good with gas aswell

posi is a must aswell better gears without it is going to leave you spinning like crazy off the line


lose some of the cars weight with alloy driveshaft and gut out the padding under the carpet

also make sure your shocks and struts are in good shape as wheel hop is no fun

or you could always look for a tbi or vortec 350 you will see a major power increse with these and all the other mods i listed will do even better on a 350

i myself wont be keeping the tbi as i do prefer tpi in looks and for how it responds
besides tpi was designed to make 305s have output near 350 range
it boost torque something the 305 needs compared to the 350 and gains some hp

i figure when im done with my lo3 it will put down around 230-240 hp and 330-340 lb/ft as ill have an lt-1 cam 1.6 rr tpi full exhaust

i figure if the lb9s with the 350 cam made 230hp 300lb/ft stock then ill be a bit higher going with all the other dynos ive seen from people that have done tbi to tpi conversions

so far from what ive seen from other tpi swaps on lo3s you get 200hp and 300+lb/ft and this is with the stock peanut cam that came with the lo3
but ive seen up to 220-330 with a good exhaust

tpi boosts what the tbi heads do good already and thats make torque you just get around 20-30 hp and 50-60 lb/ft torque


over all there is alot you can do to make these engines potent but remember that everything you do will make a 350 even more potent

 

NO WAY IN HELL THE TPI WILL GIVE 50-60 ft/lbs over a properly tuned TBI setup. Maybe 20 ft/lbs and only in a VERY NARROW powerband compared to the TBI. HP will stay the same to a possible small loss. The TBI makes a power curve that is as flat as a table top. The TPI is an inverted U.

 

Yea that post was kind of like captain obvious's nuclear missile. at least that guy read the stickies, and promptly puked them back up in this thread.

 

thats the problem with threads on this site no one wants to help someone they just say search and half the time its something not covered
i figured id give the guy some ideas as its what are my plans for my car


but i get flamed for it ya thats just great



my buddy blew the engine in his tpi iroc and found a cheap lo3 put the tuned port on and now everything is the same as with my cars engine other then haveing tpi on his and his roasts mine off the line and all day long
so to me thats proof that the tpi for a street car is better

and i still cant beat him even with now haveing better gears

he is makeing just about 200hp and 320lb/ft fw
and mine shows as 180hp and 260lb/ft fw mind you thats after 20% drivetrain loss added back up
mind you these are stock ecms not custom tunes

and being that stock the tpi cars made 205 and 300 and the only differance is the heads now id say with tbi heads and tpi you get better
output as it seems the tbi heads make torque and the tpi head make better hp



but ive also seen tpi heads on tbi cars makeing 185 hp but 245 torque flywheel

its all about compromises apperently


tbi can be made a strong setup but for how much i plan to spend on my car to get where i want to be tpi will work much better

 

We have helped more people than you would imagine. We just get tired of answering the same question 100X/ Especially if the answer is readily available on the board. There is even a sticky titled, Budget TBI Build, that would give a person MANY ideas on a TBI performance setup. It is biased toward a 350 Vortec, but a L03 could easily recieve the same upgrades.

I know you are just wanting to give advice, but here is the problem I see.

2 different cars, 2 different engines, 2 different drivers, 2 different states of tune, etc. Not a good comparison. I have picked up 30+ TQ just from tuning a STOCK TBI engine, more on a modified engine. The factory TBI proms are crappy at best. I made 325 RWHP from my cheapy 350 TBI build. The only thing exotic was the used Dart Iron Eagle 180 heads.

I have dyno'd two perfectly tuned setups. The only difference was TBI vs. TPI and the PCM. The TBI was the better setup hands down for overall powerband. It was quicker. The TPI got better city fuel mileage and had snappier throttle response. But then again the TPI was being run by a 2002 Vortec 350 PCM. Sequential fuel injection, OBDII, custom tuning by me, etc.

My L03 (from a 1991 Caddy Fleetwood) in my Truck put down 181 RWHP @ 4,300 and 268 RWTQ @ 2,900 with nothing but a pair of long tube headers, duals, L69 air cleaner, and custom tuning.

 

Reasons why the 305 Z28's with TPI engines were faster:

Dual cat exhaust, slightly better
No LO3 cam, but a better cam

And .... a better gear ratio .. rear end


That's about it

 

Fast355, I am not saying the tbi heads are worthless, but there are allot of junkyard heads that would do better, I have to know, what do you do with the metal shark fin looking swirl in the bowl to improve flow, do you grind it back to not disrupt the air path? That is what makes since to me, the motor you claimed to build was a 350 though, not a 305, have you ever cammed a engine with these heads and dynoed it?I am wanting to know what they might do, i am trying to figure out whether to junk the 3 sets of these heads for scrap or port them, they are plentiful.

 

z28s with 305s got the same peanut cam as the tbi cars unless ordered with a 5speed and g92

but there are some odditys out there that got the l98 cam with an automatic
seems more like that just happen to be the cam that was picked at the end of a shift type of deal

305 z28s without g92 came with the same 2.73 rear end same as the tbi cars

dual cat came and 305s with manual and g92

really the only differance with a z28 and a rs 305 was the heads and fuel injection style z28s did have higher rated stall converters then tbi cars

 

Threads like this are retarded. I feel bad for you "91 camaro rs".

You know I remember doing this huge amount of math to see how much power the TBI system could supply. The two barrel system....

Man we had that thing up to like 530HP possible. And now people are running MAFs and dual TBIs are capable. Crazy stuff.

Makes me want to puke when owners of slow cars down other slow cars.

Yea the LB9 was faster then the L03..ook...well lets put it this way...there both slow stock and so is the L98 lol. Sorry guys our cars are slow. The only options we have is "potential". So don't come up on here and tell some guy whos new his engine is a pos because guess what if your running any sort of stock system yours is too.

 

Yes, I have dyno'd many engines with the swirl port heads on them. Both
stock and ported. ALL of them have had the swirl vane left in place.

I have run BOTH 305 and 350 engines.

https://www.thirdgen.org/forums/tbi/...ght=garage+193

http://www.fullsizechevy.com/forums/...=183103&page=2

https://www.thirdgen.org/forums/tbi/...?highlight=187

https://www.thirdgen.org/forums/tbi/...hlight=305+van

https://www.thirdgen.org/forums/tbi/...hlight=305+van

https://www.thirdgen.org/forums/tbi/...hlight=305+van

https://www.thirdgen.org/forums/tbi/...hlight=305+van

https://www.thirdgen.org/forums/tbi/...hlight=305+van

Here is the flow numbers page compiled by Kdrolt.

https://www.thirdgen.org/forums/tbi/...-headflow.html

Here are some of my non swirl port projects

https://www.thirdgen.org/forums/tbi/...hlight=305+van
----------
ALL 1990-1992 Speed Density TPI cars, both 305 and 350 had the L98 cam in them. Automatic/Manual, G92/B4C/Without, doesn't matter.

 

If I where to actually spend money Id go with an aftermarket MPFI intake and use the 7730 SD ECM. Proven setup if your going with port fuel injecton. That way the car wont be held back. There was a good thread a while back where somebody put an edeljunk 204/214 cam with TPI and it barely made over a 180 HP. The torque curve peaked right at 3600 RPM with the TPI intake. I have that same cam, and I can tell you that by 3600 RPM, its pretty much done and out. That cams rockin' and rollin' at around 2000-2800 RPM in a 350. The TPI essentially forces the engine to peak at the same place it resonates at. With an open aftermarket intake, the engine wont be limited by having to peak at 3600 RPM.

If I where the original poster, Id just get a used roller, or slum it and go with a flat tappet cam kit/pushrods, and keep the rest of the engine as is. Then replace the exhaust and intake with something more power oriented and put some better gears out back. No need to make it complicated. Properly selected and tuned, it should make for a decent street setup.

 

so what explains the large differance with the g92 cars its got to be more then just dual cat exhaust

205 vs 230hp and 290 vs 300 ft/lb and the output differance
was the same for 89s that that had peanut vs l98 cam
195 vs 230hp and 295 vs 300 ft/lbs
manuals with g92 and dual cat had 10 hp more and 10 more ft/lbs then the normal 5speed cars with just the l98 cam alone

but 89 also had single cat y pipes at 2.75 vs 2.25 of 90-92 non dual cat cars
maybe thats the differance and why speed density was that much better makeing better hp even with a smaller ypipe
anyways fighting about tpi hp#s is off topic for talk about an lo3 that never got it

 

The soda straw sized exhaust could account for it. All the more reason to get rid of the cork attached to the exhaust ports of the stock TBI cars. The tuning was also more conservative with the TBI cars. The SD/MAF part doesnt make much of a difference with the TPI or MPFI. The only thing that matters in the end is that the engine gets the right air fuel ratio. The stock TPI MAFs where JUNK, so it would probably be better to have SD if you have TPI.

 

The 1990-1992 Automatic TPI cars had the same crappy exhaust as the TBI cars.

It is one of the first modifications that should be done on either car.

 

Very much so.

The TPI dyno you mention would correspond equally with mine. My peak torque was right around 3,600 rpm.

https://www.thirdgen.org/forums/tbi/...?highlight=tpi