91 RS Drop Top

I have 305 TBI in my 91 RS Vert. I was gonna do an engine swap, but this engine is in great shape and I decided that there is no point in getting rid of it.
So I'd love to hear big bang-for-the-buck build up options. My initial thoughts are cam, valve train, headers.

I don't really want to get into anything deeper than a cam swap.

Oh yeah, and this is my first time doing anything like this...

What kind of hp/torque have any of you been able to get out of your 305s?

camshaftxe

N20 and some gears

titan

Good advice. If you do decide to go with the upgrades, you should get a chip burnt for your setup, so everything is in tune. So many people just stick things in and on the engine and never get the chip flashed to recognize the changes.

Saculia

iTrader: (1)

I recommend upgrading the heads and the cam. At the very least change your heads out for a set of healthy 305TPI heads. Then put in the comp cams 08-500-8. Upgrade the exhaust system with a set up headers and a good cat back system, and also upgrade the gears in the rear end, go to 3.XX.
This should wake your car up a good amount from stock. After that you are going to want to do some computer tunning.

91 RS Drop Top

Thanks for the advice, both of you. I have already done the gears, and swapped in a rear-end with posi. Might be later this year before I can do the heads/cam. Any point in doing the exhaust first? I've heard the other mods will get poor results if the intake and exhaust are not done first.

Gonna stay away from nitrous.

robertfrank

iTrader: (27)

no real need for TPI heads as they really don't flow much better than the swirlies. just get the heads ported and get a 93-95 LT1 cam with 1.6 RR's, Prod. LT4 or a ZZ4 cam. with tuning you should see some great gains in power.

rocko350

camshaftxe

Cams are great bang for you buck, maybe the biggest.

Fast355

iTrader: (2)

Stock TPI heads suck

robertfrank

iTrader: (27)

If you're really set on changing out the heads there are a few options to consider.

Ported stock "187" heads
ZZ4 or "113" heads
"059" or 305 vortec heads
Standard "062" or "906" vortec heads
Ported "081" TPI heads
Trickflow 53cc aluminum heads
World Products S/R Torquers

It all depends on how much money you have to spend. With the 059 or 305 vortecs you still have a 58cc combustion chamber, no real milling involved. But you need an intake to match because your stock one WILL NOT bolt-up.
With the 062 or 906 heads they will need to be milled down a bit to get the proper combustion chamber size or you'll lose compression and like the 059 heads a new intake will be needed.

The ZZ4 heads will need to be milled down even though they are 58cc due to the aluminum dissipating heat faster and thus a loss in power will result IIRC. Also with the ZZ4 heads your intake will need the two middle bolt holes elongated due to the angle being off between the 87-88 model years.

The Trickflows seem to be a good choice for a head but at a price of almost 1200 dollars it's not really a "budget" head. The S/R torquers from what I understand aren't that great of a head and they also weigh a ton due to the extra meat left for porting.

So this leaves our stock heads. As Fast355 said STOCK TPI heads suck. If you read the cylinder head sticky at the top of this forum you'll find flow numbers to back this up. In recent years the stock 187 or Swirl port head have been shown to have great gains when ported. If you don't want an engine that breathes hard above maybe 5200 rpms and you want more torque through out the powerband stick with a set of ported 187's. Tha's my opinion, if I made any mistakes in my wording please correct me if I'm wrong. But I think I might have gotten it right.

robertfrank

iTrader: (27)

Ok if you want a REAL BUDGET build up here's about the cheapest stuff you can do in my mind that will get you into stock LT1 territory.

A small list as follows.
Port your stock heads. 1.94 intake valves, bowl blended, gasket-matched the works.
Either a carb manifold with TBI adapter, Edelbrock 3704 tbi manifold or get the stocker bored out to 50mm. You can also bore out the edelbrock one if desired.
A 96+ s10 4.3 torque converter
Auto: 3.42 gears
Stick: at least 3.73's
aluminum driveshaft (another ebay gem)
Transgo shift kit with a corvette servo
Sonnax TV spring kit (dirt cheap)
A posi unit. Either auburn or eaton but PLEASE don't get a powertrax. believe me on this one.
Tuning equipment the basics are around 150 dollars but an EBL Flash and a wideband makes life ALOT easier.
LT1 cam with 1.6 roller rockers (ebay works wonders here.)
underdrive pullies (yes they work I know from experience, they did for me atleast.)
Ultimate tbi mods (free or with very little money involved.)
and last but not least WEIGHT REDUCTION. They say the loss of every hundred pounds is a tenth in the quarter. that really depends on how far you want to go. I think all this can be accomplished for less than 1000 dollars if you look around for the right deals. Anybody else can add what they like.

F_N_JUNK

iTrader: (4)

I too am contemplating this......... I got 3 SBC's that are ready to go, but the 305 is getting 30mpg and I'm not sure I want to lose that?

91 RS Drop Top

Lots of good info from robertfrank. Already got the posi. and I had better gears but they weren't set up right and I threw a used 3.23 in their for the time being.

you've all convinced to start with a cam... Also, i have no real intent to drag the car, so I'm not to worried about tenths of a second. I would need a rollbar anyway. I'm trying to make a car that has some kick when I step on it, and can at least hang with some of the other sports cars on the street.
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Does the Aluminum Drive shaft do much much for the car? it obviously decreasing the rotating weight, but does that make a noticeable difference?

robertfrank

iTrader: (27)

When I replaced my steel one a few years ago I noticed the car would rev better and my throttle response was alittle crisper. Also I lost a vibration I used to have at high speeds with the steel driveshaft.

DM91RS

After replying to your air cleaner thread I did some reading and found this. If you are going to keep you LO3 and do things on the cheap I would improve the breather as you asked about (in what ever style you want, just no need to spend much) and do a full exhaust. (headers, 3" cat., and 3" exhaust out to a good flowing muffler)

If I had it to do over and not start out to build a track days car (later to be abandoned) I would do the same thing if my engine was in good condition as you say yours is. Mine is at 234,000, does not smoke and still runs strong. (borrowed time )

Later if the bug is still there for more dig into a cam and intake swap. BUT before that I would look into tuning before things get out of hand.......

91 RS Drop Top

Sounds like good advice. I think I'll be going for an air cleaner mod, exhaust and probably a chip for now. maybe an aluminum DS. Later this year I will probably do the cam. i' have a friend that offered to help me and I'm as interested in the learning experience as the new cam. as for the exhaust I near there's no real need to run true-dual on these. Any thoughts or experience?

DM91RS

Yep...........one 3" exhaust from the headers through a 3" inlet muffler will be more than you need for more mods than you have listed. Forget the dual BS....not worth it.

topless89

if you're going to start increasing airflow through the heads, remember that your stock TBI will only flow 400CFM. that will become a weak link very quickly.

DM91RS

I could not remember the name the other day but do a search for Beast5spdGTA. He had some documented times and dyno numbers with just a few bolt on mod's and no tuning in the beginning:

[quote]
My TBI car, with basically just full exhaust, 3.73 gears, and K&N, ran a best of 14.759 @ 92.97 mph with a 2.104 60'. The car ran consistant 14.7s and 92-93.xx mph before I swapped the cam.
[quote]




https://www.thirdgen.org/forums/orga...t=#post1273248

igotta355z28

iTrader: (1)

y stay away from nitrous, u ask for bang for ur buck performance and there is no better one. where else can u gain 100hp for about 500 bucks...if done right nitrous is fine....and just think normal gas milage and decent power from your 305 all the time, then when u need it flip the switch and bam more power.....

Fast355

iTrader: (2)

Its more like 450 CFM @ 1.5 in/hg stock. With TBI mods it is 490 CFM @ 1.5 in/hg. That is flow for roughly 285 FWHP in stock form and over 320 FWHP with TBI mods. The STOCK TBI is MORE than enough for MOST NA TBI 305 builds.

camshaftxe

its a hard thing for someone young to understand but the best advice for a 305 is to leave it alone. You will never get the performance of a near stock 350. CHP did some pretty recent testing on a TBI 305 and they really worked, but only for 260 HP and 300 ft lbs of torque. The money is much better spent on something else. 305's were made to be a cheap standard equipped engine that was good on the earth and good on mileage and you are defeating that purpose, leave it the way it is and get 20 or more MPG and save your money for something more worthwhile, besides just glancing at what you plan on doing there is no since in putting on aftermarket heads and cam with a platform that is probably getting tired, think of the fundamentals first, 305's are known for pinging and some damage may of already occured or the rings just may be just plain worn (chevy high performance)

camshaftxe

They also did an article where they put vortech heads,custom-ground cam 0.510/0.520, 210/214 at 0.050, 114-degree lobe separation angle, gm performance parts vortec tbi manifold, crane hi-6 ignition, edlebrock headers, and full exhaust,turbocity hiflow tb, 55lb jets, afpr, and a custom tune made 257rwhp, and 294tq.

robertfrank

iTrader: (27)

I think if they used better headers they could've gotten alittle more power out of it. Those edelbrock headers suck.

camshaftxe

I think with bigger injectors, hooker shorties, a true dual system and more tuning they may have squeezed 15-20 more horsies out of her. Only problem I see in all of this is that with the amount of $ vs end result, there would have been a larger gain with a different induction. Put that cam and head setup on an l98 and you could expect alot more, or even an lg4.

91 RS Drop Top

here's the deal on my car. I bought a car with a TBI because I was looking for a vert and this one was am amazing deal. The 350 TPI verts are way expensive. My original plan was to immediately swap in a 350. My money ran a little short though. And now I have a friend who said he'd teach me to do some basic stuff like the cam swap, so I'm gonna do it for the learning experience (I need it). I also plan to keep this car forever as a weekend, goodweather convertable, repaint it, custom interior etc... Somewhere along the way the car will get an L98, maybe even an LS1, but that may be 5-7 years down the road.

For now i'm looking for the best $1000-$1500 to put into it so that it doesn't get beat by mid 90's mustangs and the like. I see from lots of reading on this site that the best $1500 would probably be a used 350 TPI at 245 hp, but I'm gonna stick with the TBI for the learning experience. Right now looks like first stop will be ultimate TBI or cold air intake, header back exhaust, and an LT1 cam ('cause they're cheap an will leave me some money). Tuning will have to be in there somewhere, obviously. So if I have any money left over, what next?

Also, I keep seeing people use "fwhp" Front weheel hp? that would not make sense. i am familiar with rear wheel hp (rwhp), shaft horsepower, brake hp, etc.

What is fwhp in our context?

camshaftxe

Fwhp is flywheel horsepower, the horsepower the engine produces at the flywheel, its reasonable to asume that in every auto there is a 20% loss of power in the drivetrain, imho, I have a tbi, it used to be a 305, and now it is a tbi 356, my best advice to you is dont do anything to the 305 that cant be taken off and put on a 350. Tbis will is not to produce power, but simply to feed the engine. If you want 300+ponies, dont touch the 305, just cruise in it, have a good time and save up for an l98, a tpi kit, ls1, lt1, whatever you want, just somthing that isnt tbi. A cam of the size chp used, with vortec heads would have made 350+ horsepower on an l98, or even if that had just used an edlebrock manifold and carb. Tbi is a bottleneck. Wet manifolds dont like much cold air. Dont expect to hang around beside a mid 90s, or 80s rustang with an auto lo3, unless they have an auto v6.

robertfrank

iTrader: (27)

Ummm I think you need to stop spouting nonsense. TBI is not the bottle neck, There are people on this board who have been in the 12's and 11's with 305 TBI's, just ask Fast355, Dewey316, and the many others here that have taken TBI to the next level.
If properly tuned a TBI car WILL run circles around a carb or TPI car. Even on STOCK engines you can see a 25-30 hp increase without even touching the motor.

It all comes down to what you want. Not everyone wants an 11 second car. Due to the increase in gas these days in my eyes TBI is the way to go. I get 270 to 300 miles to the tank IN TOWN in my car. With mild bolt-ons and a good tune these engines can hang with most anything on the road.

Fast355

iTrader: (2)

Educate yourself on the performance capabilities of both TBI and the 305 and get back to me.

thomas1976

You probably missed fast's reply about tbi flow. If your engine makes less then 280fwhp dont waste time on ultimate tbi mods.

Also new aluminium DS will not make more power except if your is in bad condion or out of balance.

If I were to start over with a good condition 305tbi tg Id proceed in the following order for a fun dd

1. EBL flash
2. Free flowing cold air intake
3. Headers + complete 3" exhaust
4. TPI or Walbro190 fuel pump, and AFPR
5. Cam and heads at the same time (at least cam without budget)
6. tb mods or bigger tb and fuel injectors if needed (6. not without head swapp)
7. posi and SFC (wenn budget allows)

86firebird350

i dont see why not. i have raced several 4.6's and a couple 5.0's (many of these modded) in my basically stock (open element, 160* stat) auto L03 and although im still not on par with them just yet, they hardly pull on me at all. im talkin maybe a car and a half after a 1/4 mile or so race. so it is possible to make these cars keep up.

camshaftxe

Yea, ok, lets say 500$ for headers and catback=20hp+50$ for a 14x3 breather&good filter=20hp+ring and pinion kit for 200$, now youve got 210fwhp and good gears, take that 750$ and put it into a 260 hp 90s stang or a 220hp 80s stang and youll be right at 300+hp, IM CALLING EVERY PERSON ON THIS BOARD WITH A 12 OR 11 SECOND TBI OUT. You got one show me slips or dyno proof, yea fast355 and dewy did it but theyre masterminds that have spent years with engines and tbi especially, no regular joe is gona pull a 12 with a tbi.

mario82z28

I'd say save your money, i think the 305s are very dependable every day driver, but no power house you can get hidden horse out of them but only so much you got to really know what your doing. there is no subsitute for cubic inches, but that's just my opinion

camshaftxe

Its not the 305 part as much as it is the tbi part, so 2 or 3 people made power with a tbi, big whoop, Id be willing to bet alot that if you took those engines and put a carb or tpi on it youd make alot more power. Ive seen a few 10 second 305s, but they were carbd.

Dewey316

Your funny. What are you doing on the TBI board for anyway?

Shoot, maybe I should start selling a "L03 power-pack. $1000, uncludes everything needed to put 250hp to the wheels. I think it would be a hit.

What is so diffrent about car/tbi, other than the the fact that with TBI we have more precise control over fuel, and arguably a better atomazation then carbs. Please bring the tech on what makes TBI worse? I'm waiting.

Also, more than 2 or 3 people have had success with these cars, have some facts beyond what you read in a magazine, before you come in here spouting off that BS, there are enough of us here who have dyno print-outs, and timeslips that say my TBI can kick your TPI's ***.

Fast355

iTrader: (2)

TPI won't make ALOT more power than a properly dialed in TBI setup. The TPI is still fuel injection and needs to be tuned as well, especially the Speed Density setups.

I know of ALOT of people making well over 300 HP on TBI now. One of the members (PFK) here has a TBI suburban that runs. Here it is running 0-100.

Dewey316

I will also point out, that 3 years in a row now, and my f-body clubs dyno day, myself and a 305/stealthram car have dynoed, we have almost the same build ups, by he has a stealthram, I have TBI. Our cars have dyno'ed with a peak with 1-2hp of each other, each year. My car has a much broader torque curve, and more usable power. I also have about 120k miles more wear on my motor, I would bet you, that with fresh rings in my motor, I would make 10hp more than he does.

--John

camshaftxe

Thats a fast burb, but I think your missing my point, Im no tech, just a regular jo, and hate me if you want, but its next to impossible for a regular jo to be compatent at tuning a tbi enough so to pull 12s, O and I have I tbi. I payed 4300$ cash for my lo3 rs when I was 15, had I know Id have to spend minimum 1g to get a lousy 250rw I wouldnt have bothered with it. Put 1g into an lt1, ls1, l98, or even an lg4 and I gaurantee Id make more then 250rw. I dont understand why you would advise an amatur to invest in a tbi, you know how unpractical and down right hopless it is for them. Think about how many 16,17, maybe 18 year old kids ask you to help them mod thier lo3, do you really think they will ever reach 250rw? Do you really think they will ever theyre going to pull a 12, man get real, theyre going to go with a modded tbi,modded exhaust, drive that for a month or two, and be dying for more, if they have some help they may do a head, and cam swap, and then need tuning wich they dont know how to do.

camshaftxe

O by the way my o-100 is about 10sec, but then again my speedo is off due to a gear change.

Dewey316

Bull.

I bought mine when I was 17, I'm not am just an average joe also, it doesn't take any skill.

Dude, you have ZERO idea what you are talking about. How many LB9's have you seen put down more than 250rw HP on a dyno? How many thirdgens have you dynoed? YOu want to talk budget, think about what 1k in a TPI setup gets you. Nothing, the cost of intake parts are unreal. The LG4 also needs a new carb and intake and cam to do get the same power than an LO3 can get with a cam and intake, and some computer.

Really, stop talking about stuff you have ZERO idea about. the LG4 is a worse starting point than an LO3, regardless of what you are trying to do. The LB9 will cost more, to get the same power out of when you start talking about anything north of 230hp to the wheels. On EVERY ONE of the 305 cars that came stock in thirdgens, you have to do a cam and intake if you plan to go anywhere above 230hp, any of the fuel injected motors, will need a chip. Look at the cost of runners and lower intake for TPI, then add in a cam, add in headers and exaust, and then a cam, and you are in more money than you are in TBI, just because of the cost of the intake parts. ANd you are going to end up in the same spot. WIth the long runners and their size, you are very limited in what you can do with TPI.

Don't post again, until you have some freakin facts. Bring the tech, explain to me a how a flow limited TPI setup with is obvious RPM limiting runner length, is going to out HP a TBI car with a good intake, if you give them the same cam. The TBI has one big advantage from the budget point when you take into account the fact that to make any power with TPI you have to ditch it.

billybird

with the same money a 305 TPI car will make more power than a 305 TBI..plzz

91 RS Drop Top

Again, for the record maybe I should rephrase myself. I ALREADY HAVE a Tbi. I bought it to get a vert, cause TPI verts are like twice as expensive as LO3 verts. I'm gonna keep this car for a long time and I would like to do something to it so that is not frustratingly slow when I step on the gas. If its gonna be hard to make it beat 5.0 stangs, ok. It would be nice not to get stomped. I just want more kick when I step on it. I never plan to take it to a track or run for an E.T. I'll get a hard-top someday for that. BTW, someone mentioned stangs with 260hp. I don't think the GTs were up there until the very late 90s.

Back to the topic at hand, I have posi and gears done. I was thinking alum DS anyway because I have some vibration. Will the reduction in rotating weight help more power make it to the wheels? Next thing I look at will be the cold air intake. Can someone point me to a good aftermarket one, or should I just fab one like in Ultimate TBI mods. I'd rather buy one, but there aren't many available for TBI.

BTW, this is the TBI forum, so why is anybody who want to TBI bash in here anyway?

DM91RS

I was going to say this but you beat me to it.

IIRC you just wanted to make your car more fun as I did mine. That's all. But it always turns into my p is bigger than yours type of thing or why waste time on it.

TADailyDriver

iTrader: (8)

well im 19, and have an LO3 and if you read my sig, i have minor mods and ran a 13.738@98mph last night at the test and tune. And yes i went to a tech school for engines, but i only took rebuild and overhaul, not how to tune an engine. TBI are great engines, and i also kept up with an LS1 last night and he only beat me by a fender or so. I havent even done a cam or new heads yet and when i do ill expect to be in the low 13's possibly high 12's with the right traction and suspension setup. I havent even put on my new Nitto 555R drag radials yet and ran street tires that are pretty well worn last night. A good tune a the right setup will get you far in a TBI engine and you dont have to be a tech to do it. No yes i have put alot of money into my TBI and i have a 383 stroker pushing 550 all engine in the garage waiting for me for when this engine takes a ****, but with my TBI only having 9,500 miles cause it was rebuilt and another 10,900 on the 700R4 i think i have a long time before it gives. The only reason i havent put in the stroker yet is because i dont have the money for the suspension setup which can be a quite more pricey then engine mods. And i just dont have the time as i work 2 jobs to afford this car with as high as gas prices are..... Each engine has it own potential, and each owner has his/her own amount of money they are willing to spend. So dont bag on ppl camshaftxe for dumping money into their car just because you havent. everyone has their own opions and their own bank account. Let them do as they please with no negitive feedback. It not hurting you any unless someone in a modded LO3 pulls up next to you at a light and blows you away in a race and all your friends see it.....

robertfrank

iTrader: (27)

ok...... prove it.

DM91RS

I'm sorry but for the first time I have to drop the flag. Yes I read your sig but 13.7 with those mod's. come on......let's keep this constructive criticism....not 19 year old internet bs. Although your heart might be in the right place........

Dewey316

Plzz nothing.

It is known fact, that TPI is a upper RPM restriction, because of running length. No one in their right mind would argue otherwise. Once you stab a cam both TBI and TPI cars (same money at this point), they equalize out, they put down darn near identical times, and HP, up until about the 230rw HP level. If you cam beyond that point, the TPI because a major restriction. The only thing to do then, is spend a large ammount of money on intake parts. This is where the carbed and TBI cars have the advantage, we can get intakes that will flow more than enough air, and have shorter runners, for just $150-$200, TPI gets no where near that cost. Yes, stock for stock, TPI has the advantage, because it got a much more aggressive cam from the factory than TBI, but the second you stab a cam in either motor, then from the $$$ standpoint, TBI will get to the numbers cheaper, until the point that you out run the fueling ability of 2 injectors (which is somewhere in the neighbor of about 400hp or a little more).

Like I said earlier, this is the TBI forum, I asked why you guys were even posting here. Really you aren't contributing, you are a couple of bolt on TPI guys, with no idea what you are talking about.

To the original poster. I wouldn't bother with a cold-air kit. I would start by doing exhaust then looking for a LT1 cam, or if you want to spend some more monay, gte a more aggressive aftermarket cam, and a good single plane carb intake, and get into computer tuning. There is a ton of info on how to build these 305's to run well. It all comes down to fixing the major short fall of our motor, which is that we got just about the smallest cam that GM ever put into a small-block.

camshaftxe

Where do you get off asking why Im posting here? Im not a tpi guy, I have two tbi vehicles, Ive been working trying to mod my fbody tbi for 5 years now. If somone is going to go through the trouble of a cam, head, or intake change, all im saying is your getting into semi serious modding for minimul output. Since when does a 15psi tbi fuel pump support 400 or more hp? It struggles to feed a mildly built 350. To the original poster, if your want power bad enough to instal a cam and intake, you better go ahead and consider a fuel pump and head change.

Fast355

iTrader: (2)

I would hardly call it minimal output.

I built a mild 355 (10.5:1, Dart Iron Eagle 180s, GM Production LT4 cam, Edelbrock 3704 intake bored 2", stock 454 TBI unit, Tri-Y headers, Duals) that put out 326 RWHP.

90# injectors will EASILY feed 450+ FWHP. My Van was running 68# injectors @ 45 PSI using a stock 2" bore 454 TBI on a single plane manifold. I set the 700r4 up to make WOT upshifts @ 6,500 rpm 1-2 and 2-3. I made right at 400 RWHP from a 350 with heavily worked vortec heads and a custom roller cam.

camshaftxe

Alot more then I have lo3 cars, matter of fact aside from you and fast never. Yea Il be sure to tell my buddy with a 10 sec 305 running stock intake manifold and stock 750cfm qjet that. 13.7 with a 305 tbi on a pnut cam and swirl dorks, lmfao. Im not even going to touch that one. My tech data is this: open element=20$+good filter(k$n or somthing)=20$,headers&full exhaust=500$, on an lo3 all togather thats 200, maybe 210hp, Lb9- exact mods= minimum240hp. Take that engine in my chp post and through a stealth ram, or modified tpi, or even an edlebrock carb and factory qjet, you can believe it would have put down more than 257hp. Take a bone stock lo3 and give it an totaly kicka$$ tune and you might pull 190fwhp, take an lb9 and do the same, and geuss what you got more. I dont give a dam about induction vs. induction, thats not what I was ever getting at. What I was getting at was that the guy shouldnt go overboard with the lo3 trying to cam it and give it an intakemanifold and all that. If he has no intentions of strip racing and all he wants is mild performance, then it can be easily attained with a full exaust, and intake.
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Your finaly releasing this information lol. Ive been wondering for quite some time what the heck you were using that got 11s.