i have a 92 rs 25th ann. with a 305 tbi 700r4, i wanna get some more horse, and want a 4 bbl, i kno i need the intake, carb, and the tv cable bracket and all that, but computer wise and wiring wise, what am i getting into. i also want to get rid of all the hoses and crap over the pass. valve cover, UGLY!!!! i hate it!!!! daily driver. a/c, rather not have it, heat helps, but its a summer car, so if anyone can help, please, and let me know how to go about this swap.
thanks
keith

 

bump
also, where is my fuel pump relay on this car, i have no idea, i spent a half hour just looking

 

The fuel pump relay should be on the firewall driver side.

Since you have a 700R4 you will have to wire up a switch to lock the converter. When I did my swap, I took the entire ECM harness out. Its separate from the rest of the wiring. You wong have to run any extra wires. Don't forget you will need a non-computer controlled distributor. Also I went from TPI so Ihad to completely change my fuel pump, I'm not sure if you can use your existing fuel pump. I'm sure someone will chime in with the answer.

 

you can use the stock fuel pump but you will need a return style regulator ...I used a mallory 4309 and it works great, you will also need to run an ignition on 12v+ source to the green/white wire to the fuel pump relay or it will only run for like 3 seconds and then stop. Had a good time doing my swap but be prepared for a lot of hours to get everything right...good luck

 

Im in the same boat you are man. Ive been wanting to convert my crappy TBI on my 92 for a long time

 

This is not necessary.

The green/white wire at the relay is what primes the fuel pump - it gets it's signal from the ECM (which would be gone). This 'prime' only lasts a few seconds, and then there's no voltage to the fuel pump until the car is started. With a carb, there's no need to 'prime' the fuel system, since there is fuel in the carb bowls - it ill start, and the pump will run off the OPSU until it's shut off.

The fuel pump gets a steady voltage directly from the battery through the Oil Pressure Sending Unit (OPSU). After the car is started, the OPSU supplies the constant voltage to the fuel pump until the engine is shut off.

UNLESS - the car sits without being started for more than a week or so - after such a time, the car will start, but it's hard to get enough fuel to the carb to refill the diminishing fuel in the bowls in time. In this situation, you might want a manual switch to run the pump for a few seconds BEFORE you start the car, in order to clear the air from the fuel lines and get a consistent flow of gas to the carb.

 

so remove the computer and wiring, run a toggle switch to the fuel pump(wich i kinda already did), and put on the new parts, plus the trans switch???? dosent seem like alot, what about vats, is that in the computer or seperate?

 

i left my computer in there. just cut all the wiring i wasnt using under the hood. and used the red injector wire for the choke. here is my thread.

https://www.thirdgen.org/forums/carb...bi-update.html

 

VATS won't be affected - seperate system.

Don't remove the wiring - leave it in there - it's great - gives you unlimited in-cabin to under-hood wiring without trying to route new ones!

 

Haha that's ghetto.

 

Ghetto? Ghetto is someone 'rigging' wires all over the place, drilling countless holes through the firewall, and having a hodgepodge of rainbow colored wiring wrapped in electrical tape and having an entire gang of cheesy Dollar Tree solderless connectors falling out from under the dash everytime they hit a small bump in the road because they didn't have the foresight to understand that there was an almost unlimited supply of wiring available that was ALREADY cleanly installed, secured, and protected.

I'm very serious about this. I've installed all kinds of accessories like seperate computerized adjustable fan controllers, manual on/off switches for fans and TC lockup, installed the factory fog lght system using the factory switch that lights as original, and numerous others - all using the existing wiring harness.

Of course I'm not advocating to leave ALL the wiring on the engine side in there forever, but having this harness in tact has been great. When I finish my project, then we'll talk about what's unneccessary.

 

I'm not saying it was a bad idea bro. And if it works for you, good man! I am going to say that after you explained it in further detail, in theory it sounds like a great idea. All but the fan wire, do you burn through those tiny wires fast? I used to have mine hardwired, and used the wrong guage wire and it melted down pretty badly.

 

The magic word here is...

Relays!

The small wiring harness wires are only used to supply 12v to enact a relay to run high amperage items like fog lights and fans.

 

I am in the same boat with a TBI motor. But ,after having replaced the TBI with a carb was it worth it as far as performance??

 

thats also my question, say i got a single plane intake and an edelbrock performer 650 manual choke carb, and an accell hei cap on coil with a better coil than stock, how much better would that be as far as putting you in your seat, cuz right now, damn, HONDA!! hold on not done accelerating is my problem, i have a performance ignition system and run nothing but premium, and it sucks, it dont put you in your seat, and dosent roast the tires like it should, the cam is good and compression is perfect, and matches on all cylinders by +/- 5. i read that 92 305 tbi's only make 170 hp stock, and that sux. id be shocked if i had 200, and that sux.

 

if it is a 305 tbi i would not put on a single plain manifold. use a dual plane manifold. the most you will need is a 600 cfm holley.

 

but how much of a horse power gain will i get, i was using that as an example, cuz thats what i can get my hands on right now, but i also have a couplle holleys laying around, and a dual plane. but are we talking 50 more, 20 more?????

 

-5 to -10 HP from a TBI to Carb Swap. You can think of your L03 as a 1986+ LG4 when you convert it to carb. It loses 10 hp and 15 ft/lbs of torque.

The HP killer of the L03 and even LG4 for that matter is the factory exhaust from the head ports back, the tiny stock peanut camshaft, and the factory chip programming.

 

i dont think mine lost any power at all going to carb. as a matter of fact it runs way better. and she will spin the tires twice as much as it did before. i think it is all in how it is tuned. with the right tuning and timing i think it can make as much or more power if done right.

 

ive been wanted to do this for awhile now,

good thread!

word of advice the stock tbi fuel pumps are garbage , upgrade to a tpi fuel pump or an after market one.

and another thing my friend told me to get a carb pick up gas tank , he siad its better overall then just running a regulator to bring down the psi on the regular pump to a carb. is this true?

 

Best bang for your buck on 'in the seat' performance is a posi rear geared better than the 2.73 peg leg most Camaro's get. I got a 3.08 posi rear from a junker for $150, and it made a world of difference. Just going carb isn't going to help much - like mentioned your still dead on the motor from the heads and exhaust.

On my 1990 I did the following: #416 heads with a home port/polish job on them, and add headers ($300). Doing the port/polish on your own is about $100 for the electric die grinder and bits, then after it's done you could get a 3-angle valve job ($200), I went up one size on the intake valves (about $60 for new valves - 1.94 intake instead of 1.84, and another $60 to have the machine shop cut in the new valves), get the LT1 cam installed ($100 used), and your dual-plane intake.

BUT - for all that, you could drop in a 350 and really get the power you desire. There's no replacement for displacement!

I've never had any issues with my TBI pump - however I did replace it with a new one when I did my 350 install.

You don't need the entire gas tank - just the pickup - nothing different about the tank itself.

 

ok, get this, i went to this guys house for a friend, then him and i bullshit about his car and how the previous owner bought some parts, and all this, then he offers me a set of h.o. heads and a cam, FOR FREE, i took them, everything was taken apart, no warps, i checked, no cracks, nothing, just all taken apart ready for rebuild, and the cam just needs cleaning from sitting, its out of a 350. the heads are 305 either 194s or 196s, so im gonna rebuild the heads, put in the new cam, a true roller timing chain, and maybee throwing in the car right then and there. probably at the same time (pending the cash) throwing in my 356 posi, a high volume oil pump, new fuel pump, regulater, steel braided line kit, and alot of goodies that come along, and the valve covers ive been waiting to use, ones that have the plates that screw off to adjust the valves, damn, i cant wait
im real excited to get this goin, ill have pix and updates under my post about my new camaro

 

I switched my car over from a 305 tbi/700r4 combo to a 400 carb / th350 setup in the 89. Most of the issues you'll run into have been mentioned.

I stuck with the stock tbi pump since I had replaced it no more than a year prior. If you're running a return style FPR, it'll work great. I mounted a pressure gauge on mine so I knew exactly what I was running for pressure (tbi is too high pressure for a carb). Don't entirely remember what I did for connectors, but this is a pretty easy issue to deal with.

Wiring-wise, I yanked out everything I could and cleaned up the engine bay. The only tricky thing I had to deal with was finding switched power for the fuel pump. but a good wiring diagram will help you here.

Never had to deal with the lockup deal with the 700r4, so can't say anything about that area. Mine was shot and the 350 dropped in with the help of a couple relocation mounts/brackets.


Do give yourself some time; I wouldn't try to rush through this project in a weekend. Also keep in mind any possible emission regulations you may run into in your state. I got lucky, since my state was not testing at the time of my swap.

 

anyone got a holley 650 carb that needs to be rebuilt that u wanna sell cheap, 650 or more would be good, but pretty much any carb u got that u wanna sell cheap, let me know, thanks

 

what is the deal on the 700r4 lockup how is it done and why is it done..also will a 750 holley be to big for a 350 crate

 

the lock up in the converter is to provide fuel mileage and to help the trans run cooler. when it is locked up is isnt mutipliing torque. i have mine hooked to the rear defroster switch now since that didnt work in my car.

 

350 crate as in high performance crate yes, a 750 will be fine, in my oppinion, but if your running like me a stock 350 (h.o. or not) with bolt on ****, and a stock cam, a 650 works, the more horse u make, and the more u have in your engine, like crank, pistons, cam, then the bigger carb u want. let me know what u got, or a link to your crate, and ill let u know

 

not sure what all it has in it..i bought it for 400 bucks..and only has 3600 miles on it..it was in a 4 wheel drive and they twisted the drive line and rear end..it has a 600 on it right now ..single pump and i would like to put my 750 bowls on it to make it a double if it is possible

 

where would the wire hook up to on the tranny..how is it done ..always had a t5 ..putting my 700r4 on my 350.. i have the wiring harness from my 305 i can use..came with the tranny from junkyard

 

Sorry, it doesn't work that way. The main body. metering block, and throttle body are different between vacuum secondary and double pumper carbs.

 

its in the tech articles. i took the two top right and left wires on my aldl plug and hooked them to my switch. when i get on the freeway i turn it one.

 

alright, now about my car...... lol
now, im getting that 350 h.o., keeping the bottom end stock, re-doing the heads(of course), getting a vic jr. intake, true roller or dual roller timing chain, and a great ignition system
650 carb would be my best bet right?
and what cam should i use?

sorry if some of theese questions dont belong, but you guys seem to know what is goin one, and it seems one92rs has gone through what im doing

 

What heads are these, 3rd gen "HO", or GMPP 350 "HO"? Do you have the casting numbers?

I'm guessing 3rd gen "HO".

Meaning the same as LG4 and LU5. With 1.84" intake valves, 58cc chambers. Not bad heads, but they need some help to get the most out of them for a 350.

What is the cam? You really need to know that. "350 cam" can mean a lot of things, most of them translated "lame".

Victor Jr? Pretty poor choice for a street car. You need more cam than is typically street-friendly to justify it. And a valve train to match.

 

no, the 350 h.o. came out of a 71 corvette, it was bought in the vette new, guy didnt like it back in the 70s still, swapped it, the motor sat for 30ish years, just got rebuilt, used for a thousand or two thousand miles in my buddies 87 iroc, and then swapped out for a 400, and im picking it up in the morning. i would like to know more myself about the motor, so ill post all numbers on here to get some help, cuz i dont know anything about the numbers besides where they are.

the vic jr. was offered to me for 20 bucks, so i said yeah, why not? whats wrong with that, my dad runs that on his vega.... 1/4 mile car. how come that wouldnt be good on the street.

i want a new cam. the 350 cam u are probably meaning is near the top, i was keeping the 305 and putting 305 h.o. heads on it, and a cam that was from a 350, camaro i was told, so yeah.... that idea is out the window, but i will be selling the parts.
as far as the cam for the new motor, i want more bottom end power, and im happy with my top end power as it is, with my stock 305. its a daily driver, so it needs to be nice on my gas, cuz i drive alot, but also will be raced, im goin against my dads vega and wanna beat him, hes got a 400 small block as i said. any suggestions....
sorry for all the typing, and sorry if i seem dumb about this, i just havent done anything with cams.

 

one more thing, i CAN get 350 injectors for my tbi, now someone said that this swap is + or - 5-10 hp gain, and maybee loss....
true or false
now if i kept the tbi and got the bigger injectors regulator and pump or whatever is needed, would i still get some good hp, and would i have to change the comp?
what if i say built up the motor on the inside, kept the tbi, and got a performance chip...... am i getting some good ideas, or just ideas that will waste time, shoot i just shoot for the carb.
i just like the computer actually..... plus rather keep it to make this engine swap plug and play cuz its my d.d. and cant be down for more than 2 or 3 days at a time

 

bump, is there a difference between the 305 tbi intake and the 350 tbi intake??? i thought it was the injectors, regulator and pump were the differences......

 

Okay, they didn't call them "HO" back in 1971. And about 20 million more 350's came out of Vettes than there were Vettes made. Plus, most Vette engines (especially the heads) were no different than any other SBC. Get the casting numbers, and they can be looked up on mortec.com to see what they really are. If they are 1971 heads, they most likely aren't anything special, and would probably not be as good as other choices.

For the same reason that a good Ford intake manifold for $20 wouldn't be right. You need what's right for what you're going to use the car for, not what you can get cheap.

A lighter car with a bigger engine built for racing all mean that a 350 in a 3rd gen built to be nice on gas is going to lose.

Just changing the injectors won't give you more power. They might make it possible to support the power increase from other changes, though.
With TBI, when you change things that affect engine performance, you almost always need to change the computer tuning along with the other change.

The 305 and 350 TBI intakes are the same. The differences are injector size and computer tuning.

 

so what should i do for a comp, ill be looking for the cam, im swapping my 305 throttle body for a 350 one. the story is it came out of a vette, once again, i didnt get the numbers, but i have it here. and whats not special about spinning the tires on dry pavement at 60 with this motor in a thirdgen????? now for the comp, illl be keeping the tbi, stock dizzy at this point, but i have the msd coil, 8 mm wires, im getting a dual roller timing chain from zoom, maybee some rocker, either 1.5 or 1.6s, i cant remember wich one they are, what would be a cam suggestion, like a lift duration suggestion.... numbers???? now what comp will give work with this setup, also something that i can put a chip in one day......