so i recently picked up a 91 firebird for 800$ shes pretty much clean. its got a 305 tbi an a 700r4. the tbi has edelbrock headers and an lt1 cam swap. i just had a few questions on the tbi system itself. i know a lot of people do not like the tbi system and even more people dont like the 305 engine. but since this is my car and im gonna be the one to drive it i want to keep the 305 and the tbi. so my thing is i want to do some tuning on it. i know a lot of people are gonna see this, have a heart attack, blood will boil, then they will give me some ridiculous response. so if your gonna do that please dont give me any input at all. ....

BUT since everyone here should be helping each other! can anyone please send me a link to where i can buy all the stuff to hook my laptop up to my cars electrical so i can tune the tbi? YES THAT IS WHAT I WANT TO DO so please some one help me. i need links to everything that i will possibly need to buy and all software that i will need to download. thanks everyone.

305 is a fine engine for DD. The LT1 cam shaft is popular cam upgrade for 305. If you want to uncover full engine potential head work and free flowing exhaust are a must in addition to ECM tuning. As for tuning - you have a lot of reading to do. I would do this before spending a dime on any engine parts - it will become clear after you read tuning stickies and numerous threads.

Like I said - read first before doing anything else.

//RF

dynamicefi.com has the ebl, or moates.net for burn2 and adapters g2 or gx. tunerpro is a free app. you might look into the apu1 or the xtreme aldl for data logging.

as for now the onlyy exhaust it has is the edelbrock shortys. i plan to run the y pipe and finish out the exhaust. would you recommend a single in single out muffler? how bout a catalytic converter? im running historic tags so is a converter neccessary for anything as far as emissions? and ill have to do some reading before i get myself into something i cant fix

Technically you suppose to run CAT despite the type of plates you have on the vehicle - it is a federal regulation. Local emission inspections regs vary dramatically across 50 US states. The problem with emission testing they constantly (thanks to liberal idiots at EPA) change and hardly ever go away. The worst regs, naturally, are in California. You can not take fart here without having 'personal' CAT showed up your posterior! I might be kidding, but it is getting to be almost that bad. So I would keep the CAT and go with Y pipe into free flowing aftermarket CAT. 305 does not need too big of an exhaust and there are several vendors making complete kits with a single turbo style muffler. Keep in mind that you will need heated NBO with shorty headers.

//RF

ok so i got a cat for the car it was a universal fit for the 89 firebird 305 i had. i believe its a 2.5 in 2.5 out. which is what i want to run. a full single 2.5 inch exhaust. as far as whats done to the engine right now. what would be pushing it to the point it will run like ****? could i get away with a carbed intake with the tbi on top of it?

Your tuning links as requested sir,

http://www.dynamicefi.com/

http://www.tunerpro.net/

I will respond in your thread in such a fashion as I choose.

Dont overlook the intro to tuning links at dynamicefi.com. It is written for people new to tuning. covers tuning as well as TunerPro.

you already have a lt1 cam in it ? if so how does it run without any tuning ? don't let people get under your skin about building a 305 . in all reality with heads an a cam an exhaust an a good tune you should be able to get 3-400 hp . i think you'll need a bigger cam to get above 300 hp but i'm pretty sure 300 is possiable with the lt1 cam . vortec heads are cheap an are very good just need the ones with 1.94 vales . if you decide to use the ones off a 350 they need to be shaved a little to get your compression back . good luck with your car an keep us updated .theres alot of knowledge on this forum an a few who have taken the mighty 305 a good ways . just do alot of researching before buying parts .

I've driven many 80's trucks with the 305, and they have great power! Of course a bigger 350 will get you more if your going all out, but the big hotrod engine in the mustang was always the little 302. I've always wondered why if you had a 302, your cool, but a 305, and your not, when really the 305 can do better.

302 is 4" bore by 3" stroke while 305 is 3.735" bore by 3.48" stroke. The 'personalities' of the two engines are different. 302 is hi RPM revving happy motor, while 305 is a low RPM torque grant. The 4" allows much larger valves in the cylinder head which promotes high RPM HP output. The longer stroke 305 is good for lower RPM torque, which is what needed for a daily street driver. Larger valves in 305 are not needed due to smaller bore shrouding.
Back in the late 60' GM build 302 by installing 3" stroke crank used in 283 into 4" bore blocks used by 327 for SCCA racing circuit. Interestingly enough 3" stroke crank re-appeared in 1994-1996 'baby' LT1 (L99) 4.3L (263CID) motor. I have been toying with an idea of combining a crank from this tiny motor with 4" L31 block to build a modern (one piece RMS) version of a 302CID. The problem is that these engines (L99) are hard to find due to a small production run and factory cast cranks should not be pushed past 400HP. But I digress - sorry.

//RF

it runs pretty good actually. it sounds great with the open headers but i need exhaust lol. i like the 305 and i do want to build it up but i am always scolded by everyone that its not worth it. or that its "gay" but its definitely a great strong small engine. i will give everyone an update as i get a set of heads and try this tuning thing out

how about starting here.

https://www.thirdgen.org/technical-articles

I run a High flow Magnaflow cat and its reputation for being a quality piece is second to nun ,and the Magnaflow 3in. cat back with a cross flow duel outlet in stainless steel seems to be popular. I run a American Thunder 3in. Flowmaster 80 series cat back because I like the Flowmaster sound and its volume.

I have an eaton posi with 4.10s

Its been a long day ,I just re-read your signature and corrected my reply.

im gonna settle on the flowmaster catback and do a straight after the ypipe and have it welded into the exhaust. im a little tickled pink right now looking at the swaps people can do on the electricals. i want to do a ls pcm swap i know ill need to repin but is it worth all the hassle?

No way, no how. I don't think your a good candidate for that swap anyway.

The EBL is a shoe-in for this application.

bad news everyone. hours got extremely cut at work. i cannot afford the car anymore. so im going to be getting my money back that i had paid towards it. so no more third gen... BUT i plan to get one SO until that day.... GOOD LUCK TO EVERYONE AND ENJOY YOUR THIRD GENS, i know i wont be enjoying walking to work everyday(18 years old) thanks for all your help with my should have been project

good new everyone. everything worked out. i ended up getting the firebird!!!! so i got a few more questions. what size is the inlet tube for the tbi on the back of it?

are you still looking for this info? im surprised nobody has responded yet, i got a spare TBI i can get you the size of the vacuum port on the back if you still need it

well if his hours got cut he is probably just driving it. Lack of funds tends to cut the mods. I just find it funny how many people jumped on the dropping a few hundred on getting all the custom tuning stuff even before the cheap and easy stuff (bumping up fuel pressure, injector spacer, free flowing air filter, good tune-up, bumping timing, shift-kit, etc.)

I can understand the hours being cut, i can barely scrape together cash for parts my car actually needs, but you also gotta remember, apparently this car already has an LT1 cam and 4.10 gearing(which is too steep for my liking on a mostly stock L03 IMHO), which in itself needs to be tuned(not necessarily because of the gears but the cam), he could also do what i did, i got all my tuning needs used on here for under $100, then spent about $50 on the stuff to convert my ECM to use 28 pin chips from Moates, everything is great with it, im just still in need of headers and a Y with the 02 bung in it and a wide band kit

all in all this car will benefit greatly from a tune as any thirdgen would even if its stock, but i agree the free/cheap stuff should be taken care of before he dives into any real money spending.

yes i still need the sizes on the back on the tb unit. and sorry been a while. finally got some good hours back. i am starting with all the cheap stuff that needs to be taken care of first before i go diving into some outrageous and expensive build/tune. i am wanting to sell the gears and get a set of 3.42s or 3.45s. i havent done much to the car at all honestly. i still need to replace the shocks/struts, and im doing a complete brake overhaul on the front end. rotors bearings seals calipers hardware lines master cylinder and brake booster. as far as the rear they seem fine and i dont want to dump money into the rear end because i may end up swapping a 4th gen rear in

im a newbie to website dont know how to post message. but my problem is i have a 305 vortec with tbi heads and tbi intake its running rich and only will stay running if i unplug IAC, i put a new IAC in cause i thought that was the problem but it does same thing, can anyone help me. do i need to get the 305 ecm. the auto had a 350 in it

L03 injectors are smaller than a l05 you might be able to get bye with lowering the fuel pressure but injectors are easy to find at the wrecking yard just have then cleaned and flow tested. The Eprom should be changed as well. You can find those easily based on the ECM service number and EPROM broadcast code to identify them. I think I have 6 of them laying around

its very unlikely someone would put tbi heads on a vortec block.is this in a camaro?camaros didn't come with vortec engines though one may have been swapped in.we need more information.

it has this right here 305 vortec block with tbi heads and tbi intake the throttle body is off 350 along with the ecm cat is cut off with flowmaster added. one 02 sensor on driver side unplugged no 02 sensor passenger side. i bought for $150 car and motor and trans with title cuz the owner could not stop it from running so rich in fuel. it only stays running if u unplug iac i thought it was a bad iac so i bought another and same problem.

Plug in the oxygen sensor, the car would run worse as it warms up with no 02 reading. Make sure you don,t have any exhaust leaks on the lh bank as well it will trow off the reading of the 02 causing it to be excesissivly rich.

Sorry I forgot to grab the specs from the tbi when I got home,

But you have a 305 block with a 350 ECM? Wouldn't the fuel tables be way off with that prom? I would think you would be better off grabbing a stock 8746 ECM with prom, and then adjust the tune as nessicary

Maybe I'm wrong but I would think using an ECM from a 350 would be a bad idea on a 305

i will switch out the ecm and plug in o2 sensor but it is that why when i unplug the iac it runs better

It could be, your ECM is adjusting the iac based off of 350 specs, which would be horrible for a 305

Keep in mind, this is what my brain is coming up with, someone can correct me if I'm wrong

can anyone please tell me what these two wires are for? i just had the car towed home and i was going through and found quite a bit of interesting rigged up things. beginning with the fan. it had a kill switch mounted to the radiator tower. i was wondering what these wires are for. do they connect together? i found a wire ran from one end to the switch then from the switch a wire was ran to the other end. i also noticed on the cylinder head there is no sensor in on the passenger side. shouldnt there be a fan switch there? someone help me. its gonna be a daily driver in exactly 1 month

Is the wire in the picture the one running to the kill switch your talking about?

Is the old fan switch location plugged with something?

An is the old connector still there?

If not they probably chopped that connector and rewired it to the new switch

the wire in the left picture had a wire running off of it to the kill switch and a wire was coming off the other side of the kill switch to the wire in the right picture.

where the fan switch is supposedly suppose to be on the passenger cylinder head, there is nothing there.

it still has the original connector for the fan

Unfortunately I dont have quick access to my car or I would check what that wire was originally for,

But if there is nothing where the original fan switch would be I would think coolant would be pouring out of that hole when the car is running..... I know when I changed mine a good amount of coolant came out in the few seconds it took me to get the new switch in position

thats the thing, this car was all rigged up with ingenious modification(sarcasm) theres 11 quarts of oil in the engine and theres no coolant so im going throw now fixing everything, is it possibly that i can just reconnect those two wires? or am i better off capping both ends and running a different fan relay and plugging that hole in the head?

also do you know what size the intermediate pipe is for the 305 tbi exhaust? i am looking for a muffler but im not sure what size it is. since i have to order the intermediate pipe too

I would run a stock fan switch, I've only had to change mine once since 07' and it hasn't failed since, I can get you the stock pipe size tomorrow(I'm pretty sure it's 2.5"), along with the TB inlet size, for the tb are you talking the fuel or the vacuum port on the back

ok great! and yes the fuel inlet size. my fuel line has rusted so bad that its leaking so im looking to getting some fittings and possibly running maybe a braided line for the inlet and outlet.

any new information?

i'm curious also as to what size lines would be needed to replace the stock fuel lines . i want to add a aluminum manifold an it will be a bit higher an i need a fuel pressure regulater so why not get braided lines . just not sure what ends or size .

thanks ronny

ok so i got the fuel line figured out and i got my ypipe in today. i measure the end its a 2 1/4. so thats what my headers/stock exhaust will consist of. all stock up to a flowmaster. i do not plan on using this engine to make power at this point. i plan to run it as a daily driver until i build my 350 or something.

my baby


headers im running(came with it)


my engine bay, shes a real mess right now only because its only all the way together.

Sorry I've been slow at getting you the answers I've been promising, I was just about to post 2 1/4 for the exhaust, I measured my old cat back yesterday,

Luckily Ronny stepped in with an answer

Hope you start getting everything straight with it

Not sure if you want to spend this much but regardless check the puh fit efi line and fittings from Aeroquip/Summit. Makes the job easy and reusable as well. No leaks

well i was a bit shot down by the fact that these ugly edelbrock headers did not fit the stock y pipe. does any one know where i can get a y pipe for a set of 68723 series headers? i also found the water pump to be making a terrible noise when its spun by hand so that might need to be replaced. aside from that once i get the alternator and battery ill be able to give it a test run and see how it sounds and how it runs. sort of afraid to pour a ton of coolant into it if its full of sh*t so ill probably pour some water into the intake and let it run through before i put the hoses on it and pour some coolant in.

Does not Edelbrock/Summit offer the mate for that header? I would call summit.

i have looked everywhere for this thing. its such a buzzkill because i just bought the gaskets and bolts then i went ahead and installed them. i guess ill go with the flowtech headers and y pipe. i know that the quality of that isnt the best but its all i can afford and i dont plan on making this car a performance type. just something i feel is comfortable and can be daily driven. the flowtech i dont see any problems with its just enough size for a 305. 1 5/8 primaries 2.5 collectors and a 2.5 y pipe end. ill probably run a full 2.5 inch single exhaust with dual outs.

i currently am looking for a good set of shocks and struts. i hear a lot of good things about the kyb gr2s anyone have an good experiences with them?