justcallmeclassy

iTrader: (1)

Alright so I've been planning to do a L98 swap from a 85 vette into my L03 92 rs for a long time. It seems like its going to be a real pita to actually get this done, much worse than I expected but still manageable. My question is I've heard its much much cheaper and easier to just swap in the 350 and leave the TBI system, so how different would it perform, if at all, if I ditched the TPI? Somebody told me id loose torque, and i would rather not. Would it be worth it? Thanks

justcallmeclassy

iTrader: (1)

Also I already have 350 TBI injectors, knock sensor, etc off a truck so there woulldnt be much to buy I don't think except a chip, please correct me if im wrong, im young and need to learn lol

InfernalVortex

iTrader: (4)

I think TBI as a system has a lot more potential than TPI. TBI, if you can get big enough injectors, will pull well past what the TPI can handle. The problem is figuring out what injectors you need and where to find them. Finding big injectors isnt an easy task.

But I think TPI is a useless POS EFI system better suited for trucks than sports cars.

You may lose a little peak torque with the TBI, but they wouldnt use that system in trucks if it didnt make enough torque. The injectors atomize the fuel very well, you get plenty of torque right off idle. My buddy with a TBI 350 and a T5 says he can roll around at 15 mph in 5th gear just idling around no problem.

justcallmeclassy

iTrader: (1)

Wait you're saying tbi will pull better than tpi? Are you sure? it was the tbi that was on trucks, and its what's on my car now. The tpi is what's on the l98 now

justcallmeclassy

iTrader: (1)

Ok so if I keep the tbi will I need a new fuel pump for the bigger engine? And how big of injectors should I get, would the ones of the truck work well?

InfernalVortex

iTrader: (4)

Its just my opinion. TPI is tuned for torque, but TBI injectors atomize fuel so well that even though it's a wet system it still has excellent torque right off idle. And face it, these are big v8s. You're not going to have to worry about torque.

TBI I think has much more potential since it isnt crippled by those long runners that cause a 350 to run out of breath at 4000 RPM. It will just flow as well as the intake (Which can be changed) and the throttle body will allow. you dont have an intentionally engineered power curve that cripples any sort of decent aftermarket cam.

Like I said, the problem is finding injectors that flow enough fuel, and at some point the throttle body's cfm limits. I think I read the factory throttle body can support around 350hp with the right injectors, though.

justcallmeclassy

iTrader: (1)

Well I've heard some people say tbi is awful, and then I've heard some say its just as good if not better than tpi. that's why I was asking so thanks for the input. I think im gonna stick with the tbi, it'll be so much easier and cheaper anyway and if it'll make the power then I don't see anything wrong with it. Besides I think it'd get better mpg which is always good

Ronny

iTrader: (1)

I would keep the TPI engine, swap in a better cam, port the heads, and discard the TPI manifold. Use a single plane Edel Vic JR or Pro products same with a Edelbrock elbow with the TPI TB unit.

justcallmeclassy

iTrader: (1)

As a 19 year old going through college and working part time at a walmart, my options are extremely limited ...

notoriouscamaro

LOL. That was funny. Well, using TBI would certainly be easier as far as keeping everything the same under the hood. You can sell the TPI system as well. Im thinking about doing the same thing with my RS.

justcallmeclassy

iTrader: (1)

Yeah I've decided this is what im gonna do, and I was planning on selling the TPI but then again idk how much they're worth. I saw one sell for 250 on craigslist about a month ago... seems a little ridiculous to me

notoriouscamaro

DO you plan on going with an aftermarket tbi intake?

justcallmeclassy

iTrader: (1)

Not at the moment no, in the future more than likely. As of now im just gonna do the ultimate TBI mods listed on here and try and get the 350 in the car within a month

Ronny

iTrader: (1)

TPI system is fine. It is just limited when the owner wants more performance. Other aftermarket manifolds avalable will allow that additional performance. TBI has limitations as well. Design constraints exist.

LAFireboyd

iTrader: (3)

GM did this, essentially. Research the LO5 engine; it's a 350 TBI.

Ronny

iTrader: (1)

350 TBI. YUP a cop car caprice or truck.....I forget what the HP was on cop car maybe 170?

Drew

iTrader: (58)

The pro is it'd be a 350... the con is it'd be TBI.

You might want to ask around in some other places then just the TBI fan-boy forum. Ask over on the TPI forum, or on the engine swap forum. TBI is a joke to everyone but it's enthusiasts. Not that TPI is all that much better for producing maximum power, but what GM was doing was tweaking the intake to make power at a low RPM. The idea was to make up for other short comings, and produce a fun to drive car without resorting to mileage and drivability killing performance parts. If you want a car you can drive and have fun with, TPI works. If you're going racing you probably want a carburetor. TBI doesn't really have a home.

thomas1976

Interesting detailed pros and cons.

IROCmenace

iTrader: (1)

I have had all three, carb, tbi and TPI all in a thirdgens. As well as LS1's and LT1's. They all have their benefits and drawbacks.

TBI was probably my favorite as far as simplicity and ease of working on it. Great driveability.

My dad's 87 350TBI truck made 200 HP and 300 ib ft of torque stock, L05

A 350 TBI will be better than a 305 TBI performance wise

TPI is fun but I hate working on it. It is tempermental and parts are expensive, numerous and some are increasingly hard to find. TBI was used on alot more platforms and parts are easy to find and cheap. $40 at a local pick and pull for a complete tbi unit beats 250 on craigslist for TPI anyday.

a 4 barrel Carb is fun with a stick but in an automatic I didn't notice much difference between it and a throttle body car expect for easier tbi startup.


You just have to sit down and find out what it is you want. For a street driven car you can make about the same gains with a TBI as you can a TPI. If done correctly. It just depends on what system you like the most. Many times I have thought about trying to trade my 350 TPI for a 305 tbi car for the simplicity.

thomas1976

If the car has TBI, there is absolutely no pro for converting to TPI.

Just for reference, by the time you need a larger TB for the TBI, you will need a lot more parts to upgrade the TPI.

justcallmeclassy

iTrader: (1)

Didn't the LO5s have crappier heads and cams than the L98s? so mine would be a little better than that.

Anyway I know everybody else veiws the tbi as a joke, but id been told it'd be basically the same power and much cheaper to install and keep going. Its not like ill be doing anything major for a long time, maybe some long tubes but I really can't afford much at all. So for what im doing the tbi seems like the best route, and im gonna take it

thomas1976

In general those people are only capable of and maybe a coolant bypass on a TPI TB. Leave alone modding and tuning an engine with EFI.


Yes the L98 corvette engine has better heads and cam then the LO5. Should find out what head, cam and CR it has, this will make the tuning and fueling alot easier.

You will need to fuel and tune the TBI system (TPI or similar fuel pump, VRFPR, EBL flash http://dynamicefi.com/) you could eventually get away with fuel pump, AFPR, 350TBI injectors and coustom chip.

Otherwise you are better off to just swap everything over from the corvette.

Also do a search for accessory fitment and intake bolts angle, using 85 corvette heads in a third gen.

InfernalVortex

iTrader: (4)

I just dont buy this whole notion that TPI destroys TBI in performance. At all.

In 1992 LB9 cars made 205hp, and L03 cars made 170hp. That's 35 hp split across 083 heads which are DRASTICALLY superior to the swirlport heads. And I think in 92 the LB9 cars had a bigger cam too, while the TBI cars had the small cam. The TBI cars got horribly tiny exhaust systems too with terrible manifolds. The TPI manifolds were terrible too but not nearly as much.

And you really think the intake manifold alone is worth 35 hp? Its worth at most 10, and to me it's crippled once you get to the point where you are putting in cams that are optimized for performance powerbands. It's easier and much, much cheaper to put a Performer RPM intake with a TBI on top and make power than it is to mess around with all the crap the TPI guys have to deal with to raise the RPM range just 500 RPMs. Decent runners alone will cost you over $300 by themselves.

Fast355

iTrader: (2)

It is NOT worth 35 hp itself. The 1987-1988ish LB9 single catalyst engines with the peanut cam made somewhere around 190 HP if memory serves me correctly. That is only 20 hp up on the lowly L03, which also managed to run alot less than optimal timing advance and fuel delivery compared to the LB9.

UnderCover89TBI

iTrader: (25)

A TBI on a TPI engine performance wise will be very similar. The thing that holds back the stock L03 engines are camshaft, heads, and cubic inches. Stock tpi setups are done at 5000 rpms. TBI's L03's can go a little more but pretty much done also. A TBI on a TPI engine will do more than 5k. Now gm designed the TPI engiens that way. That is why they came with a 305, the 350 TPI engines only offer like 15-20 hp more than the 305's because of teh limited air supply. You can upgrade the runners, manifold etc. but every system has its limitations. I'd run the 305 TBI setup on your l98 see what she does. If you are not happy you can save up for a holley stealth ram, or some other induction setup.

IROCmenace

iTrader: (1)

I agree, but don't forget the torque difference, you will make more torque with a TPI over a TBI because of the runners. That is why 5.3 trucks have tall runner intakes and LS1's use the low profile runner intakes, truck for torque and car for HP Just depends on what you want out of your car. I personally don't drag race and love the seat of the pants pull of the higher torque off idle of my L98 and my 5.3 Vortec in my Sierra.

myzblubyu

I put a crate motor in a 1988 Formula in 1994 that was a factory 305 tbi with a 5-speed. I used a TB from a 1990 454ss. That car ran like a raped ape and got 30 mpg on the highway...

UnderCover89TBI

iTrader: (25)

yup that is it. I do drag race though. You need to spin 6k rpms on the street minimum. IMO.

thomas1976

I also owned a 91 Z28 5.7L TPI, nothing to write home about, except all the future plans you have to make it faster.

freaky

someone said ilarge injecters are hard to find ? ebay sells them or you could just get a tbi from a 454 but your gonna have to way to tune it . dynamic efi has the solution for that .as a matter of fact they have a computer that will allow you to run two tbi's so a duell carb manifold with tbi adapters are possiable . just an idea .

freaky

sorry to thread jack but heres an idea for the lo3 ,vortect heads ,lt1 cam , an a performer manifold with the dynamic efi to control the bigger injecters for those knocking the lo3 .

justcallmeclassy

iTrader: (1)

The L03 I have in the car now has LB9 heads and a LT1 cam. Its a pretty good improvement over what she had to offer in the begining, but I still just wanna go 350 lol.

justcallmeclassy

iTrader: (1)

Ok does somebody know exactly how much more torque a TPI makes? Really right now I just wanna get the motor in with or without TBI, whatever I can afford for now, and in a few years when I've got enough extra $ to go 383 ill get a better intake.

UnderCover89TBI

iTrader: (25)

Just do it then!

thomas1976

Not anough to make it quicker then the same engine with a tuned TBI on top.

freaky

you can always put a cam in designed for torque .

IROCmenace

iTrader: (1)

"Not anough to make it quicker then the same engine with a tuned TBI on top."

True but then you get into comparing stock TPI vs tuned TBI. I was speaking from a stock POV. From what the op wants to do he is just trying to see what system he wants to build on later on. You can do a multitude of things with an SBC. I am not knocking TBI, as I said before I loved my TBI in my Formula. But I also like staying close to stock. And TPI delivers more torque stock.

thomas1976

This has alredy been pointed out in post #22.

The LO5 engines came with ridiculous cam and heads from the factory, to take advantage of raised compression, better heads, better cam require at least fueling and SA changes.

I like the TPI too, but if the car has TBI, and performance is the goal, then converting to TPI is pointless.

TBI to TPI probably comes down to about 10-20 more torque and 20-30 hp less.

IROCmenace

iTrader: (1)

Not really.

InfernalVortex

iTrader: (4)

Do NOT get hung up on torque, please. This is going the wrong direction completely.

In colloquial usage, saying "I want torque" is saying "I want less horsepower". You want an engine tuned for low end torque and you're wiling to sacrifice horsepower to do it, there's no point in changing from the TPI or the peanut cam or the crappy long runners in the TPI system or anything. the advantage in my mind of hopped up TBI setup is that it's not limited by an intake designed for torque (and gas mileage).

And again, dont fret over the TBI not making enough torque. That system was used in trucks and heavy full-sized cars for nearly a decade. They would NOT have used that engine in trucks and full-sized, heavy cars if it couldnt make torque. That EFI system itself can make as much torque as the engine is built to make.

Horsepower = torquexRPM times a constant.

When people have cars and they do performance upgrades because they want more power, what they're doing is increasing the engine's efficiency at higher RPMs so that it produces more torque at higher RPMs. In most cases this shifts the torque curve higher and you may lose some at low RPMs. Universally nearly everyone in the v8 world accepts this as a worthwhile exchange. Nearly everyone in the import world does too, even though their engines never had enough low end torque to begin with.

Examples of upgrades that do nothing more than increase the engine's efficiency at higher RPMs:

porting cylinder heads
large volume runner cylinder heads
larger valves on cylinder heads
larger camshafts
headers
larger exhausts
siamesed runners on TPI intakes
larger throttle bodies
short runner intakes

The main solution - higher gear ratio at the differential, and after that a loose torque converter. Only once you get to a situation where you have a full heads/cam/induction 350 with a big ol' notchy cam in it, will either of those be necessary, and you'd be surprised how far you can really go without needing to do either.

And just having a slightly tuned L98 without an aftermarket cam in it is NOT going to get anywhere near close enough to a power band where you're going to need shorter gears. If you want torque, go swap to a stock L05. It'll make all the torque you want from 500 to 2000 RPM and then it will done, but that's an engine designed for torque even more than the L98 - but that's because of the cylinder heads it has, and the small camshaft it has. It's not tuned by its intake manifold the way an L98 is. The L03 and L05 engines are limited by terrible cylinder heads and a terrible camshaft. They are terrible because, again, they are designed for low-end torque. They're terrible from a racing point of view. They're perfect for towing or pushing around heavy full-sized cars.

The larger a cam shaft the more power you will make, but you will have to make it at higher RPMs. There are special grinds of cams you can get to increase power under a certain rpm range, like what some people do for TPI's, but if you got a proper intake and a proper cam that didnt have to deal with an RPM restriction, you would make a lot more power with most of the same measurements. The sound of a car with a large camshaft is precisely because the car runs badly at low RPMs. It's tuned for higher RPMs and runs much better there - therefore it makes more horsepower. The larger the intake runners on your cylinder heads, the higher the RPMs you can run and the cylinder heads will still be able to flow efficiently. The bigger your headers the more your exhaust can flow and facilitate high RPMs, etc.

High-end torque, or horsepower, is the name of the game when it comes to performance cars. If all you want is torque, there are plenty of stock 70's smogger big blocks that cant break 200 hp but do 350 ft lbs of torque all day. Notice no one seems to want those engines, though... at least not without some work done to them - because they're all torque and no power.

IROCmenace

iTrader: (1)

Maybe you should read the op's first post before you write a book on physics. I believe the op didn't want to lose torque. I am going to go ahead and unsubscribe that way all of you Toilet Bowl Injection, biased, narsasists can preach about how great TBI is even though new technology is MPI not TBI. But hey Maybe a TBI LS1 would make 2000HP and only 100 ft lb's of torque so you can get to the speed limit real slow, but hey and the end of a quarter mile and screaming at 5500 RPM's you will be flying, even though the guy that got off the line with his torque left you about 5 minute ago. This is once again turned into "one persons opinion is better than anothers" instead of answering his first question, which I tried to do. And I guess I should have figured that as the TBI board is one of the most defensive biased boards on this site. Which I figured out WHEN I HAD A TBI and as I already said, I LIKE TBI, but I guess I could have bashed the heck out of it if I wanted to and got all kinds of TPI people to join in but hey, HOW WOULD THAT HELP? I was trying to be open minded and give him info that will help him NOW; not a few hundred or thousand dollars from NOW. But hey I guess you guys could have been like almost every other new post on this board ends up now and just said DO A SEARCH!

UnderCover89TBI

iTrader: (25)

Mod just lock this thread down!

thomas1976

You are right, if he swaps the LO3 TBI EFI with the LO3 tune on the L98 shortblock, it will be like putting the L98 TPI EFI with L98 tune on the LO3 shortblock.
A rubbish engine combination, both will performe really bad and make less hp/tq then a stock thirdgen with the LO3.

This is what I meant with, "it has already been pointed out in post #22"

Fast355

iTrader: (2)

TPI will only make more torque in the MIDRANGE. It is designed to resonate and have a TUNED effect at approximately 3,200 rpm. It will signifigantly boost torque in that RPM range with a trade-off on both ends. TBI on a single plane is probably the most flexible as far as a broad power curve.

UnderCover89TBI

iTrader: (25)

I'm dreaming of a day when smog man dissappears and I can run a good intake on m y car

InfernalVortex

iTrader: (4)

Who said I was responding to the OP? Im responding to potentially bad advice given to the OP. Understanding the principles behind how these things work is how you enable people to make their own decisions about what to do instead of having to go to a message board and get a quick answer based on someone else's internal criteria on what is the best compromise of cost, speed, and reliability etc. And let's face it, most people are ignorant when it comes to these principles, forever taking stabs in teh dark and building underperforming combos. Most people here do not fall in that boat, however.

seanof30306

iTrader: (4)

Sigh ..... I've been inactive here for years, and nothing ever changes.

Your getting all emotional and "defending" TBI is like the guys 30 years ago INSISTING 2bbl carbs were superior to 4bbl carbs.

You can slice it any way you like, but the plain simple thruth is TBI is the 80's EFI version of a 2bbl carb, and a lot of the points you make in "defending" it actually prove my point.

You point out that a TBI 350 had heads that weren't as good as those on a TPI 350; that a TBI 305 had heads that weren't as good as those on a TPI 305, as if that were some sort of conspiracy of unfairness perpetrated by GM against the TBI fanboys of the world.

Have you considered why that might be?

Why did GM make 2bb 327 and 350 Camaros? Why did GM make 307 Camaros (pretty sure all with 2bbls)? Simple, because they were cheaper to manufacture, and therefore cheaper to sell. They were also cheaper to insure. GM knew (as did every other automaker), that there would be a significant segment of the market that wanted the panache' of driving a cool, "sporty" car, but couldn't afford/didn't want to spend the money on/couldn't care less about the higher sticker prices associated with high performance options. TBI Camaros and Firebirds were the 80s versions of that.

Sure, there are a lot of deficiencies inherent in TPI, but there's no question that GM intended TPI to be it's high performance induction setup; hence the fact that there were no TBI Corvettes, and GM abandoned the closest thing to TBI on a Corvette, Crossfire Injection, in favor of TPI.

I love my TBI Firebird. I bought it over 8 years ago, and it has always run perfectly. In the past 4 years, I haven't put anywhere near a thousand miles on it. I start it up every week or two and drive it around the neighborhood every month or so, yet, last month, when my daily driver was out of commission, I put insurance on it and drove it daily for a couple of weeks, and it ran like a champ, starting first time every time, running smoothly, and getting over 20 mpg.

That said, every time I watch Motorweek and see them review a base-model minivan with a V6 that makes 100 more horsepower than my Formula and runs 0-60 and the 1/4 mile faster than I can, I cringe.

I go back and read that article about the badass 305 with Vortec heads that we were all raving about a couple of years ago and realize base-model Mustangs, Camaros, or Challengers all have V6s that make 40 more horsepower than they got and I cringe.

That doesn't make TBI bad, it just makes it what it is, a low-cost, low tech, induction system that was never designed with performance in mind.

Let's make it really simple, and compare the differences between an l03 and an lb9 using simple, deductive logic:

lb9 heads - performace (compared to lo3)
lo3 heads - not so much (crappy, actually)

lb9 cam - performace (compared to lo3)
lo3 cam - not so much (crappy, actually)

lb9 induction - ?
lo3 induction - ?

Pretty obvious

When I bought my Firebird, I didn't know much about TBI. I knew I wanted a black Formula with a 350, a manual transmission, good paint, good interior, and no rust. I quickly learned you couldn't get a manual with a 350, and decided the manual transmission was more important to me. My Firebird fit all the other criteria, so I grabbed it up.

Had I known the difference in performance between a TBI 305 and a TPI 305, and thought about how the limitations of the TBI would multiply as I considered swapping to a 350 or 383 later, I would have passed on the car and waited till I found a TPI car. I'd bet that many of the people who have TBI cars on here would say the same thing.

Despite that, though, I love my car, and I'm glad I got it. I just changed my plans to fit it. I'd much rather have a 450 horse 383 in it, but I'd have to gut a perfectly good car to get it, so instead I have a 90 horse KZ650 (but that's another story). I've been meaning to sell my Formula for years, but just can't bring myself to do it.

As far as OP is concerned, your TBI L-98 may actually settle a long-running "discussion" on here. Every time the TBI/TPI comparison comes up, the TBI fanboys cry "foul" because of the swirl-port heads and peanut cam. In all this time, I don't think anyone's ever put a TBI on an L-98, which allows an "apples to apples" comparison.

Of course, when the L-98 makes less power with TBI than it did with TPI, they'll find a loophole, they always do.

EDIT: Fast, when I talk about "TBI Fanboys", I'm not referring to guys like you, Dewey, etc., who have pushed the envelope with TBI so far. If anyone ever does the 400 horse TBI, I think it'll be you. You'll probably tune it with a Comodore Amiga and a bunch of banannas and install it in a snowblower, but it'll make 400hp with a broad, flat torque curve!

robotic_junky

My 2 cents. Put your TBI on the L98 and use the 350 TBI parts you have for it. It would help to get the computer tuned. Later down the road if you want something better then go with Stealth Ram, Super Ram, Ram Jet, Mini Ram, or single plane MPFI manifold. Then go with a better cam and heads. I wouldn't mess with TPI since you already have TBI. Like everyone else has pointed out to upgrade the TPI, it cost money so much that people go with a different intake manifold system.

92firebird 305

soi have a few questions im geting a 350 l98 today for 250 from a friend of mine its got the 113 heads he said its out of a 89 vette he thinks im gonna put either a lt1 cam in or lt4 cam in and i have a 305 tbi now and i wanna stay tbi i also have a 350 tbi unit intake tbi and injectors should i just use the 350 tbi unit it self and put it on the l98 once i rebuild it how much power might i see out of it the lt4 cam has 218/228 lift is 492/492 can the 113 heads work fine with that in stock form im gonna put new valve springs on it what else i might need i know timing set thnaks for your help.

Ronny

iTrader: (1)

Try the TBI unit you already have. When you datalog WOT if your MAP readings are 95-100(sea level) you should be OK. If not(restriction) you then need to move to a 7.4L TBI unit.