i just registered, and i assume this question has been asked like a billion times on these boards, so sorry in advance. i own a 91 RS with a 305 TBI of course, and am going to for sure ditch the LO3 and 700R4 in about 1-2 years, when i get enough money, and replace it with an LS1 (or LS6 if i get lucky and find one from a wrecked Z06) and a matching manual tranny. i know this is gonna bit more than a little pricey, which is why it's not happening any time soon. however, until then, i'm stuck with an LO3, and nothing against TBI fans, but quite frankly i hate this motor. 170 hp/225lb-ft is horrible for a 5 litre chevy V8. the car came with a K/N intake, and flowmaster 80's, which helps somewhat. anyways, i've considered getting a used 305 TPI setup from either eBay or a junkyard. will this swap cleanly without having to do significant mods? how much will this cost (parts)? also, what type of power gain can expect from swapping the TPI on? and lastly, the main reason i'm getting the LS1/LS6 is the 28-30 MPG it gets. however, the 350 HP the LS1 puts out is pretty appealing too. could i possibly get this out of a 305 TPI without running ridiculous psi's and compromising my gas mileage? thanks for the help.

 

You should be able to get really good gas mileage like that on the highway right now with your stock setup. Don't bother with a TPI swap you won't gain that much power and TBI gets really good gas mileage actually. A TPI swap won't yield much because the TBI engine got the worst cylinder heads and cam of basically any V8 engine GM produced.

You're power problem is not in the TBI. If you want power you need to remove the restrictions. Get headers and full 3" exhaust to start removing those restrictions. Honestly though if you plan an LS1 swap just leave the car how it is and save all the money you can because you're going to need it. and FYI your motor puts out 255 ft-lbs not 225.

 

BronYr summed it up, especially in his last statement. Don't waste money on tpi, especially if you plan on a crazy swap like an ls1.

No offense either, but I seriously think you're better off just building a performance engine and go with a t-56 from an lt1. Granted, LS6s are monters, but that's even more money. LS1's are nice as well, don't get me wrong, but my combo cost much less than if I were to put an ls1/ls1 tranny in there, and I will leave them seeing my tail lights. Oh yeah, that's with my little 'ol tbi. Like I said, I'm not knocking the ls1, they are awesome engines, but to swap one into a thirgen costs that much more.

As far as gas milage goes, I was getting 26 mpg hw with the old combo and untuned chip. 3.73s as well. Only got 24.5 with the rpm airgap on there, but once again that is running pretty rich at cruise. I expect 27 mpg or so when I get her fully tuned in.

 

thanks for the advice. yeah, the ls1\ls6 swap idea is both crazy and expensive, but the power potential that both of those engines have with modification is unreal, and is worth the high price IMO. considering both engines get 30 mpg when completely stock, the gas mileage potential is pretty crazy too, especially for an american V8. thanks again for the advice though. i've never really toyed around with the 305's they put in 3rd gen f-bodys, so i'm pretty ignorant about them.

 

If you're going LS1 in the future, dont waste the time and money on TPI.

I'm collecting parts for the swap now. I have the 350 H.O. crate motor. Adding it all up, I'll be spending well over 1 grand to get the car where I want it and for the future of supercharging.

1)SDPC Vortec TPI base - 400
2)AS&M Siamesed Runners - 475
3)Hotrodlane.cc TBI to TPI harness - 689
4)new walbro 255 fp - at least 199 (?)
5)Misc ****, +200 I believe
Total - $1963
I got an 85 IROC TPI setup with 24lb injectors for 150..everything minus the wiring harness, which I didn't want a MAF harness anyway.

I don't want any junkyard **** and my pockets can afford going new, but its going to take a lot of money and time. Just warning you ahead of time...

I'm either doing the TPI swap or just going to sell the car and get a really nice 90-92 f-car (if I can find one that has a fresh a motor as mine) or a 94 up Mustang GT. I'm tired of screwing with TBI and I feel your pain about TBI...I don't have the patience for it plus I think its fugly.

 

I've heard the TPI is good for 20 additional hp. If you're going to upgrade it further though it seems that TPI will be much more expensive than the tbi. Unless you're planning on going over 350 hp i dont think the tpi upgrade is worth it.

Now if you've got the money (and the job) to save up for a ls1/6 go for it. The power potential is definitly greater plus you'd be dropping a close to new engine in your car. always appealing. save every penny.

 

TPI will never give a stock LO3 an additional 20hp. Saying that unless you plan on going over 350hp TPI is not worth it? Are you implying that a TPI setup will support that kind of horsepower? Stock TPI will choke the life out of a 350 horse engine and to get it to flow enough cost big bucks as you see by Fredless's listing above.

Fredless, isn't there some other route you could go with that motor without spending all that money on aftermarket TPI stuff? Is there any kind of Superram setup that can work on Vortec heads; I just couldn't see spending that kind of money on all that TPI stuff, you may be disappointed in the end.

 

Yeah, except fredless's prices are off. I feel incredibly sorry for anyone who pays $200 for a walbro 255 and $600 + for a harness. Walbro pump=$100, TPI harness from a junk yard in nice condition= $100First off, any time you mod a car you are going to run into problems.
Next, I can tell you right now a stock tbi, ultimate mods or not, on the 350 H.O. motor is just stupid, and to base your hypothesis on how tbi works on the your engine based on that is just as lame. Yeah, you may have enough fuel outta those little 55pph injectors, but thats only because your engine is so starved for air.

Yeah, there are pains with tbi, but I can garrentee it is the simplest form of fuel injection to work with, unless you go completely aftermarket(i.e. commander 950). Go ahead and swap to tpi, and you will open up a whole new slew of problems. Trust me, I have seen the problems with TPI. My buddies Z28, AFR heads, LT4 hot cam, SLP runners and base, 24pph inj, adj regulator, 58mm throttle body, etc, 383. Decked out huh? Yeah, it is, but problems with his TPI/chip tuning yeild him 100mph traps if he's lucky. If you don't have the patience for tbi, then you are not gonna make it a day with tpi. Shoot, it takes me two seconds to adjust my fuel pressure. Swap to tpi and install the afpr. Then see just how friendly it is to adjust.......

 

Hence the question next to the fuel pump...

That hotrodlane.cc is the easiest and most complete harness, at least according to my research.

The painless seems to be the biggest pain in the *** if you want to keep everything, which I do...Although I like that its labeled.

The new GM is approximately 4-600 dollars depending where you order, Dal Lambert charges no where near 241 like the article suggests...if it did, I would buy that GM TPI harness in a heart beat and figure out what goes where.

My choice for a harness is either one designed for this swap, or a new GM 90-92 TPI harness and ECM...and they cost about the same...I said above, I don't want any junkyard ****. Its just my opinion and I'm entitled to it and you can feel sorry for whoever you want.

To my knowledge, they make no HSR or miniram injection for vortec. Hell no I'm not spending any more money just to unlock another 20-50hp by buying standard heads.

I'm hoping this setup will flow at least 600CFM. GM gets the 330hp/380tq numbers for my engine via a 600CFM carbureator. I hope the long tube runner TPI will get me close to unlocking it while supplying decent gas mileage...and nothing was more disappointing than running a 15.6 with TBI...IMO, I hate it, it sucks, and its fugly. Wow, maybe with tuning and gears I'd get mid 14s...Big deal..friends 4 banger RSX runs mid 14's all day long and he doesn't have much done to it..Whats wrong with this picture.

I was just telling him my route and how expensive TPI was going to be and just to skip it and go LS1 if he wanted to go through that trouble anyway.

 

i usualy try to stay out of these TPI/TBI discusions.

but i am going to add something to this.

in stock form (even ported plenum, base, ect) TPI cannot make more than 280HP. period, end of story. we have all seen many many dyno results to prove that. it gives you some nice dyno number, and a good SOTP feeling, due to the tuned runners giving you a torque spike at 3500rpm, but beyond that IMHO TPI is junk. it never should have been used on a sports car. it is very well suited for a truck, but that is about it.

when it gets into modding TPI to make more HP, you are looking at a few options. HSR, MiniRam, SuperRam. all of them are VERY GOOD options, and can, and will make tons of horse power. but look at your price tag for that. if your goals are not 10's (i assume with a 350HO engine, your goals are 13's, or heck even low 14's. (if your goals are faster than 13's the HO is not the right engine choice, at least unmodified, it needs better heads, and more cam to go faster) a $350 670cfm TBI unit will get you there. there are several people who run 13's all day and all night with TBI on a 350HO engine. imo for what the engine is, that is doing pretty good. that is faster than most 350 TPI cars run. considering the heads/cam combo, i really doubt TPI on engine, all things being equal, is going to perform any better.

Fredless--15.6 with a 350 and TBI there is something seriously wrong there. you need to start looking at the basics, and tuning accordly. my STOCK 305 TBI runs 15.5 hopefully 15.2 range when i put the headers on. i have a feeling that with a 670 TBI, and tuning, you would be really suprised with how well the TBI performs and drives.

 

15.6.... Like Dewey said, there are people running 13s with the same engine and tbi. I can think of two right off the bat. (Hint) Ones a moderator, and the other has a beautiful intake, passes smog (working egr), and gets around 28 mpg hw if I remember right
Actually, Dewey was right on about everything. Though you are right Fredless, you are entitled to your opinion
Here is mine. You can say that you hate tbi. You can say it is fugly. But imo you contradict yourself when you say tbi sucks, yet you're swapping to tpi....... Peronally, I think both are stone age fuel injections. But I am not a rich man, so tbi is an efficient choice. I also know enough to be able to say that money I could spend on tpi and getting it to perform would be better spent elsewhere and make me more power.
A couple more opinions. $1963 for a TPI set up? Wow, that is ridiculouss. I can go out and buy a complete Holley Commander 950 4bbl Projection system for less than that, which comes with everything you need, including the fuel pump and a nice and new wiring harness.
Oh, and it's ok to buy a used tpi from somebody, but a harness from a salvageyard isn't good enough? I have picked up a few things from salvage yard, and I don't think it is "junkyard ****"
One more thing, if your so hard core about getting rid of tbi and want performance, why are you using stock vortec heads. Granted, they are nice for the price, but if you are gonna be so hardcore about wanting a different fuel injection, why not swap heads? Get better flowing ones, and you'd have a much larger choice in intakes.

But it's ok. Swap to TPI, make fun of tbi all you want. I will still beat you, even with my "junkyard ****". I'd put money on it that 90% of the guys running tbi on their 350 H.O.s will have better times than YOUR car as well.

 

Awww heart felt...Was that supposed to hurt my feelings?

One, I drive this car a lot. I want Seat of the pants feeling. I want the clean look. I want low 14s, maybe high 13's. I'm happy.


Do some research, already tried the 454 TBI swap...The damn IAC sensor kept ****ing up. I tried every possible wiring config...Nothing work...different chips etc..I put the stock TBI back on and I forgot how great the car ran.

Stone age fuel injection? thirdgens are stone age cars in comparision to todays cars.

Where am I supposed to get a LTR TPI setup? Go to GM and get it new? Umm no. Its metal, its not going to be ****ed up.

Go ahead, you can use junkyard stuff...thats cool with you, and frankly, good for you. Pat yourself on the back, you have a 13 second car. I'm happy for you.

I hate throttle body injection...Flame me all you want. I know I have tuning issues as well, I'm ignorant to DIY also. Hence why i'm using a craptacular 350 TBI chip. I still run rich at WOT...chip tuning, I know. I'm also using the 305 harmonic balancer so the timing is set "by ear." Another set back..I'm also using 2.73 gears...no suspension mods either. Right now, I'm saving for subframe connectors, my gears to be installed and a torque arm...as well as new shocks,struts and springs before I even think to install the TPI.

Also, i'm happy with 280hp..I'm sure my car would dyno not much above a mildly modded L03 at this point.

Wow you're the bigger man now..brag that your car can beat mine now and in the future..Obviously you're trying to compensate for some short coming in your life. I hope you have a happy holidays. Good day.

 

My setup gets 22.4 mpg highway, probably 14 or worse city from the heavy foot and loose TC.

 

Really, from a WOT performance standpoint, it really doesnt matter too much what is on top. The intake processes happen so fast taht fuel pretty much dumps in no matter whats on top. The things that do matter are 1) airflow, 2)engine combo, 3)TUNING. Good tuning is the capstone to any setup. Even my runs like puke 'hecho in mexico" 350. Even that engine has surprising performance once its in a 'semi-decent' state of tune. Tuning is everything. If you dont know how to burn proms, then you shouldnt really even be using one of these older tbi/tpi systems on your modified car. Its really that important. These old 8 bit machines are incredibly rigid and cant adapt as well as the newer pcms can to changes in tuning. It doesnt know what the engine wants, you ahve to tell it. Thats one of the reasons that the tpis work so much better off the bat. Theyve been tuned for more agressive engines then the lame *** l03. Theres so much that needs to be done with one of these, or any ecm for that matter. Things like fuel trim, customizing the timing curve, toning down/disabling the throttle follower, dialing in the pump shot, and so much more. I used to hate the the tbi before i got into tuning, but once its tweaked a little bit, its not that bad. The only real advantage to a stock tpi system over, say, a tbi, would be that its a dryflow system so it doesnt have some of the inherent drawbacks that can eb a nusance with a wetflow system. Airflow isnt much better, and youll have to fight the 'tuned' part of the tuned port if you want to make power over 4000 rpm. A problem that carb/tbi doesnt have. You can tune it any way you wish.

 

Same with me...but you have much more chip tuning than I. My gas mileage is fallen off a cliff since I put the 350 injectors in...But at least it cured the WOT knocking.

I have the 2100 stall converter...I know I seriously need chip tuning.

 

This is what we're all trying to tell you. You need to ditch the small block TBI and go with the Holley 670. I've seen many posts about the 454 TBI not working out, including yours, and concluded that the solution is the Holley no the BB TBI.

What everyone is telling you though, if you stay TBI it will cost you much less but you will HAVE to get into tuning the chip yourself. Also, if you go the TPI route you will also HAVE to get into chip tuning. With either of these fuel injection setups you are going to have to tune it. If you don't want to tune the computer for your combo, you need either a newer fuel injection setup with a more advanced PCM or go Carb.

 

Fredless,

if you are adiment that you will not get into chip tuning, your best bet is to put a 89 or earlier MAF tpi system in. it is the only chance that you will have a car that will be somewhat responsive to the mods you did. this is the world of FI, welcome to it. welcome to the 80's ALL our cars realy on the computer, it is a simple fact of life with modifing cars now. you have to do the computer work too.

the good news is, the computer work IS NOT HARD. it is not something to be feared. if you can use a calculator, and type. you can fix your problems.

also, if you are rich at WOT, and have a knock problem... and you say you set your timing by ear.... well i think you know at least part of your problem.

 

ok...although unrelated to the topic.

I'll make one last ditch effort to try the 670.

I'll need an edelbrock performer RPM and where do I buy that plate again? I don't see them on turbocity...Have to ask them?

About the tuning, I'll look on ebay for some cheap *** P133 Laptop or something and just buy all the ****...You guys are right. If I still don't like TBI, I can still use the DIY prom crap.

 

Yes I said stone age injection. I was trying to get across to you that spending close to $2,000 on TPI is imo, a bad idea. If somebody is going to spend that much, I would think the wise thing to do is spend a little more and go with a state of the art MPFI. I see your situation like this. A new Holley 670 TBI and new Walbro HP 255 fuel pump will cost a little over $400 and will net results better than your $1963 tpi swap. And I say that because you do not even have a larger throttle body in your list, thus limiting your upper HP.

Honestly, the only stuff I picked up from a junk yard was may caddy tbi aircleaner housing and the tpi aircleaner for my ram air. Saved a lot of money as opposed to buying from the dealer, and the stuff was in excellent condition. Honestly, the point I was trying to get across was that there are many people who purchase stuff from junk yards without a problem, and you trying to offend people who do by calling it **** is wrong.

And you know what fredless? I WILL pat my self on the back. As well as all others that have performance and TBI. For you see, we have not given up so easily.

13.4 seconds. Yeah, that's in the sig. And yeah, that was many mods ago with no traction. You know what happened when I tried to get new times with my new setup? I shattered my clutch on launch. I can promise my car is well past the 13 sec bracket now.

Honestly, as it is now, you are one of those people giving tbi I bad name. Give the Holley TBI a try like you said. Then if you still don't like your results, sell the setup.

One last thing in this post. I was bragging about my car. It is fast, and the stunned look on people's faces when I tell them it's tbi under the hood is priceless. But I don't normally go around talking trash, it's only when people disrespect anybit of my hard work, in your case, bashing tbi. And the whole short comings in life thing.....Man you are into the wrong hobby to be making childish statements like that.

John, I was refering to S-D's car on the gas milage

 

Concerning the Holley 670 swap.

Make sure to get the unit with the delphi injectors. If you buy it new, the unit will come with them. You want the #502-6 which comes with the 65pph injectors. If you buy a unit used or off of ebay, make sure it does not have the black have sphere caps on the injectors, those are the old holley injectors and no good.

You will also want a fuel pump. I would not trust the stock one for anything past 250 fwhp

The intake is your choice. If you are serious about the 670 swap, you may want to do some research and look into single planes.

Holley makes the adapter plates. But honestly your best bet is to go with a spreadbore stlye intake and make your own or have a machine shop make it for you. It cost me $20 to have one made for my old spreadbore intake. Squarebores are another story though, and would be a lot harder to fab up. Holley makes an adapter for it, which I am using, but I am not happy with it.

Also, this is just a recommendation as far as the chip goes and just to get you started. You can go to tbichips.com, and give him your info on the engine and tbi. My guess is that brian already has worked on chips for the 350 h.o., so he should have a chip that is pretty close to what you need. It is only $30 for the chip. From there, you can fine tune what you need. And like you said, if you still want tpi, then you already have all of the burning equipment.

Good luck

 

You're right. You're the bigger man, I'm sorry. I don't feel like arguing anymore, to each his own. I still think TBI is ****ing ugly and I can call junkyard **** all I want...as you can call me stupid for buying new...Lets agree to disagree...I'll tell you whatever you want to hear so you can go and be happy.

Also - I already have a TBIchips.com and I told him NUMEROUS times I have the 350 H.O. crate motor...Weather or not he did anything or not I dont know. It seems to me I have a generic 350 TBI chip designed for a Caprice.

 

Thats probably what it is. Just a warmed over caprice 350 chip with some adjustments.

 

If your still using a stock pump or plan on running near the stock fp rating with a mild motor it might be a better idea to go a tad over your desired flowrate with the Delphi units since their rated at a higher pressure tehn the standard ones. At 4k where my engines peak power is im at 85% duty cycle with the 65 pph holleys at the stock pressure. If youll be switching to a HP pump then its not much of a concern.

On a more interesting note, i *think* delpi now also makes replacement injectors for the old style mopar units. Dont know if the design has been improved or not, though.

 

Alright Fredless you can be a smart a$$ all you want. That is fine. But you still do not manage to prove your point. And I did not call you stupid for buying new (even though you'll take a second hand tpi-why not just buy a new accel if you need everything new....), I called you stupid for what you based your "tbi sucks" decision on.
*you are using the stock tbi that flows less than 500cfm
*you are using the stock fuel pump
*you are using a chip that is meant for an engine with 100 hp less

Using the stock TBI is an obvious problem, but the stock fuel pump is a killer too. Sure your fp may be good at idle and while revving up, but I can almost garrentee you that the pressure drops when under load, well at least for engines making over 250 hp. Also, if you're using a stock caprice chip, that is not even close to the 350 H.O. More than likely, I am guessing you don't have egr with the vortecs on there, hopefully you had brian disable it
Further more, as you stated you are running rich, have a knock problem, and adjust timing by ear. All will slow you down dramatically. Obvious, very obvious answers are to lower your fuel pressure and retard your timing! And that is assuming you swapped your knock sensor and esc module to the proper ones after your engine swap.

Also, the only true way for tbichips to get your chip correct is with winaldl log data, which i assume you do not have seeing as how you do not have a laptop yet (please do not take that as a knock! it is not). As it is now, all tbichips can do is take a stab in the dark at getting the chip right. Use winaldl and send him that data, and he will be able to make adjustments as needed.

Lastly, it is not about me being the bigger man. Honestly, I want your car to be fast and whoop up on mustangs, imports, etc. Seriously. But where I have a problem is that you lack the ability to get your car where you want it with tbi, and based on that, you are telling people just how "bad tbi sucks".....when in fact it is your inexperiance (yes I am being nice). Yeah, I didn't have to say anything and let your opinion be the only one on this post. But beyond it being bs, maybe a newbee were to read it, swap to tpi, and $2,000 later, be severely disappointed when he or she realizes that the money could have been spent much more wisely.

Personally, I don't want you to tell me "whatever I want to hear". Disagreements can be educating. Or as in this case, they can be fun. I guess you beat me on the junkyard **** topic But seeing as how you appearently lack the ability to properly set your timing and fuel pressure, well I find it amuzing that you blame your woes on your injection.......

Anyways, come back with your shrewd comments in respects to what kind of a person I am, big, small, short, long, whatever, and then a It is still not going to hide the fact that you obviously don't have a clue about tbi.

 

Dimented,

I think that holley underates there flow ratings. But that is just from personal experiance. It is still a good idea to get a better pump though anyways like you said. I could only get around 16-17psi if i remember correctly with the stock pump, and it would drop down to around 8-9psi when under load after the engine and injector swap

Actually, you can only buy the delphis now, unless you find a place with old holley overstock. The only trick is that you need to purchase the new style injector pod which runs around $80. The delphis are much slimmer than the older style injectors, as is the injector pod. I would think that a slimmer injector pod would make for more airflow, but who knows, Holley still rates them the same.

 

1)I ran out of money at the time...The crate motor plus shipping, tax blah blah ran around 3 grand. I'm eighteen years old, just finished my first semester at college. I HAD to skimp on some things. One I did not think about was the harmonic balancer...Hell I'm glad the motor runs and gets me from home, to school, and to work and back each day. Yes, it is jimmy rigged right now and yes it is slow. Faster than my L03, granted. I also skimped and bought the flowcrap headers, which was a huge mistake...I should have spent the money on the better heddmans and just skipped the MSD ignition because I'm sure I would have seen a better gain with better headers than the MSD setup.

2)I had one weekend to do with this swap. I work at Wal-mart...Hence why I go to school...I hate my job, nonetheless I get 40 hours a week and decent pay for working bull**** produce. I scheduled the weekend off to do the motor swap...I had time constraints and I had to ask for that weekend off 2 months in advance. Meaning, my friend and I HAD to get that motor running that weekend...We didn't, but I just worked on it on my days off and at the time he was out of a job so he could help me on my week days off. I ran out of time and money for a chip and 350 balancer to set the timing. Hence why I just gave tbichips.com my specs the best I could and asked him to disable the speed limiter and EGR and to rush me the chip...The car ran extremely rough with the stock L03 chip.

3)Yes, you are right about my inexperiance, BUT in my limited experiance, TBI is hard to make power with and to me, its still ugly and more ancient and inefficient than TPI. I respect your opinions that you think differently, but drop it, you're not changing my opinion and i'm certainly not changing yours. My age also ads to my ignorance factor and I know, so far in my short life, TBI is hard to make power.

I have the GM VAFPR...Its a little hard to turn it back. PM me to continue this because it is unrelated to the topic. I got my point across, you got yours across. Agreed?

 

Agreed.

Everybody has to start somewhere. I know when I started off, I was so confused. People telling me to ditch the computer, swap engines, this that and the other. But as it goes, I am happy with my outcome, even if it took spending money twice on certain things.
I hear ya on the money thing too. I just got outta the air force at 22. Went to school full time as while in, well except for when the war broke out. And I had a leach for a girlfriend at the time, and I was too blind to see it. So what money didn't go to my ex girlfriend, college books, and living expenses went my hobbies, mainly the car. And through my ex girlfriend came my beautiful daughter. Expensive, but very worth it. So regardless to say, money is an issue with me, and spending it wisely is important. Now with my new job, 60hr weeks are common, but I keep telling myself just 3 more classes!

Just a helpful hint as well incase you redo your headers. I have the heddman headers, and I do not like them. The metal around the primaries that bolt to the head is thin, and mine warped, thus making for frequent gasket changes. The copper gaskets won't even seal the stupid things warped so bad, so it is back to constantly blowing standard gaskets. I also wish I would have had them coated. Oh well. Live and learn
Also, though you don't feel it now, the msd will help you in higher rpm when you get your car running where you want it.

 

True that... Ill definatly need a better pump if i do any mods. Theres not much safety margin left with the present setup.

Dont quote me on this but i remember seeing that delphi carried a direct fit replacement injector for the old mopar units. I wonder if theyve redesigned them? If they did then it would really make life easier for the older holley owners. They could just pop in quality in place of the dumpy mopar stuff. I have the mini delphi units in mine so it doesnt really matter much to me but its probably worth looking into if one has one of the older units laying around.