CarburetorsCarb discussion and questions. Upgrading a Third Gen carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
Welcome to ThirdGen.org!
Welcome to ThirdGen.org.
You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join the ThirdGen.org community today!
I would just like to let you all know that I get 17 miles per gallon with my built 350 in average city/highway combo driving. Yeah, I have 2.73 gears, which makes a difference, but I am getting nearly the same mileage as my old 305 TBI got. I have a higher stall converter, also. You can see all of my mods in the signature. Just wanted to let you all know.
About 13-15mpg strictly city, and about 20-22 mostly highway (no lockup switch)
Also, I noticed an increase of 1mpg when I switched from standard 10w40 to Mobil 1 10w30.
This ad is not displayed to registered members. Register your free account today and become a member on ThirdGen!
__________________
Sponsored Links
Registered users do not see this ad. Click here to register for free!
I actually used to get 25+ mpg highway w/ my 305 TBI and 3.23s. Now I get ~21mpg w/a 350. You might have had something wrong w/your old setup if you only managed 21mpg.
BTW I got about 21mpg w/3.23s and now 20.5 mpg with 3.73s on the highway. If I were you I'd get 3.73s
Originally posted by EPAisGAY I actually used to get 25+ mpg highway w/ my 305 TBI and 3.23s. Now I get ~21mpg w/a 350. You might have had something wrong w/your old setup if you only managed 21mpg.
BTW I got about 21mpg w/3.23s and now 20.5 mpg with 3.73s on the highway. If I were you I'd get 3.73s
When I can afford it.
<--- college kid living on his own, working for $7/hr
I have a 305 TBI right now with 3.23, stock th700r4. high flow exhaust and cold air intake, and i get like 22 average driving, and like 25+ highway, looking to do 350 tbi swap now.
my 310/700r4 w/ lockup/4.10 rear with the old holley 600cfm vaccuum secondary netted me consistant 22mpg on the highway. about 15 in town. WAY better than todays big SUV's!
Originally posted by zoomzoom26 I have a 305 TBI right now with 3.23, stock th700r4. high flow exhaust and cold air intake, and i get like 22 average driving, and like 25+ highway, looking to do 350 tbi swap now.
Token:
I really enjoyed your audio clips in your sig. "Exhaust clips: idling (130k) revving (100k) lopey! (160k)" Thought I'd share mine: Idling and reving (4mb)... and yes, that is a quadrajet.
Specs for the engine are in my post on this page.
Haven't gotten around to checking the mileage yet (keep doing WOT blasts) but I think it isn't going to be too good...
Last edited by Supervisor42; 01-21-2006 at 10:53 AM.
What did you do about your higher pressure stock fuel pump when you switched to carb on your L98? i really don't wanna pull mine out and i'm looking for alternatives. i tryed turning it off and using a 4psi pump further down the line but that didn't work cause the new pump couldn't pull fuel past the old one. so can i leave my stock pump in and maybe get a fuel pressure regulator to turn it down a whole bunch?
Originally posted by specvgini What did you do about your higher pressure stock fuel pump when you switched to carb on your L98? i really don't wanna pull mine out and i'm looking for alternatives. i tryed turning it off and using a 4psi pump further down the line but that didn't work cause the new pump couldn't pull fuel past the old one. so can i leave my stock pump in and maybe get a fuel pressure regulator to turn it down a whole bunch?
I'm guessing that is more expensive then this one from holley, it was $75 Cad http://www.holley.com/products.asp?product=12-803BP .They aren't a standard regulator, being that it has to have a return line. A lot of them out there are just one in, and two regulated outs. You need one in, one regulated out, and one just out.
Yea you will have two fuel lines buy the drivers side fender well. One will be 1/2". the other 3/8" I beleive. It was awhile ago, but I think the larger one was the return The regulator is all marked, just don't overtighten the lines in. I just took the regulator and lines to Brafasco and Cummins hydraulics, and they made everything I needed with all the fittings for me for like $20. Things may be a little different for you, but I just took out ALL the wiring from the passenger side, including all the wires to the ecm. The fuel pump will not work, I just wired mine to a switch that I put in the ash tray (no one ever smokes in my car, ever). This is very easy since the wiring for the fuel pump is right behind the back seat if you lift the carpet. I beleive the pink wire was power, but use a test light to make sure . The best way would be to wire to a oil pressure switch, but this way if someone steals my car they won't get very far Also, depending on year you may need to grab a vss box from a wrecker to get your speedo working correctly.
ok i just got back from my local car shop. they are prett reputable, and the guy there said that going that rout wouldn't be good because the fuel pump will burn out.. i've been trying to figure this out for a long time now and all signs keep pointing tords pulling the damn pump out. so i'm gonna just do it and get it done. now my question is whats the process of bypassing the old pump? just a straight hose?
Is the intank pump on the q-jet equipped 3rdgens the same as the tbi pump? I am asking because I replaced my mechanical pump with a Carter OEM replacement fuel pump, and I chucked the CC q-jet in favor of a q-jet from a 78 Z28.
It was running OK till I hooked the power to the fuel pump back up. Now its rich enough to melt your eyes out.
I have checked the return line to make sure it wasn't plugged. It was OK.
__________________ <<<I don't have Attention Deficit Disorder, every body else has Attention Surplus disorder.>>>
<--- college kid living on his own, working for $7/hr
yea.. and when gas is 7 dollars a gallon... lol Anyway, go work for a parts store if you have an interest in cars. They need younger people with a will to learn rather then old dogs that cant learn new tricks. Check the vendor review board for details. OR! if you know computers, get a tech job that starts at 11+hr with no experience.
For the topic, my 305 got 20mpg when I did a carb swap. But yea, the 650 is to much for it, even with smaller jets. Its all I got and I'm replacing the engine before I replace the carb!
Ok i'm still freakin lost about this whole switch over. i'm reading what u guys post and what ppl tell me around town and everything contradicts eachother. this is what i've gathered:
By removing the intank pump and ecu i won't have gauges that work properly.
If i geet a pressure regulator and keep the stock pump i was told that would burn the pump out.
And i can't leave the in tank one in and run another down the line and simply turn off the intank...
i would like to do this the way its supposed to be done. and everyone says thats to remove the intank pump. well then how do i get the gauges to work correctly without using the ecm? cause the whole point is to get rid of all that. my main question is do i need a completely different sending unit or something from a carbed car? i donb't under stand how the intank pump is bypassed...
You're taking what has been stated that was wrong and corrected by others as the facts, in most cases.
- The gages don't feed through the computer. No effect.
- If you keep the in-tank pump operating, you need a regulator that includes a built-in return, i.e., that regulates pressure by returning excess flow to the tank. That type of reg will maintain a constant flow through the in-tank pump, keeping it cool and keeping it from burning out.
- At least you got one out of 3 right, which is acceptable in baseball. Although some have reported leaving the in-tank in and unpowered without problems, the wise course is to remove it if you aren't going to use it (use it or lose it, you know).
- To by-pass the in-tank, remove the sending unit, remove the electric pump from the sending unit, add line to extend the pick-up tube down to where the in-tank pickup was, put a pick-up strainer on it, reinstall the sending unit.
Gas gauge is not ecm controlled, atleast my 85' wasn't. Fuel pressure is a sender, just keep the old one. Tach will work. Coolant will work if you keep the sender. Voltmeter will work. Only problem you may run into is needing the vss for your speedo, try it and find out. The thing about removing the pump or not is personal opinon. I have seen A LOT of people do it, and not seen one fail. In fact, a discussed it with a couple mechanics and they said it seemed like a good idea. Its up to you if you think its "right" or not. And no, I would never cut a hole in my trunk to get to the sender
i'm in the process now of removing it its just a tremendous pain in the ***. now what your saying has been done a million times i would imagine so i'll take your word for it. thanks
i bought that holley bypass style regulator and it fixed my problem. instantley started up and ran at 6-7 psi. perfect solution to this problem. pulling that tank is just rediculous on a gravel drivway in october in newyork lol thanks for the help cars running good. Only issue i have now is that it over heats easily, which i have no clue and i'm ironing out and i haven't connected my kickdown cable yet.
Originally posted by specvgini i haven't connected my kickdown cable yet.
Then don't drive the car. You're burning up your transmission.
It's not a "kickdown" cable, it a "throttle valve" cable. It varies pressures and such inside the transmission based on throttle position. If it isn't connected, the transmission is going to assume the throttle is at idle, pressures will be low, transmission is dieing a cruel death.
i did mine a few weeks ago i just put a piece of hose in the spot where i took the pump out of, i wouldnt use the electric in line pump unless your cam dosent have the profile for the mech pump. The muffler will be in the way getting the tank down and so will the heat shield and a couple of bars. Took me a couple of days but i didnt work on it very long because other stuff to do. My filler neck kept getting in the way getting the tank down so i cut the filler neck in half and put a piece of radiator hose on it to put it back together.
Originally posted by five7kid Then don't drive the car. You're burning up your transmission.
[/b][/quote]
That depends on the transmission… if the valve body is stock then no, it goes into a “limp home” where the line pressure gets jacked up to protect it.
If it’s a modified valve body then it depends on who did what to it. Transgo puts a spacer in the TV that does the same thing as stock, but more so, but some others allowthem to go soft (which for the life of me makes no sense, cables break sometimes and you need to still get the car home).
Most likely unless someone did something dumb no cable is OK, just unpleasant to drive
exactly what I did! This is the ultimate regulator, you can put a fuel pressure gauge on it and still have a free port for race fuel injection!
BTW: Those who did the mallory regulator setup, can I see some pics? I had to run softline to my regulator from the hard line, want to know how you routed your lines and what you did to them. I'm thinking of some braided mesh or heat wrap.
my father and i are both running stock mechanical pumps for a 1985 z28 and he is running 11.7's and i was running 13.0's with the 305, but plan to run deep into the 12's with the new setup.
You're taking what has been stated that was wrong and corrected by others as the facts, in most cases.
- The gages don't feed through the computer. No effect.
- If you keep the in-tank pump operating, you need a regulator that includes a built-in return, i.e., that regulates pressure by returning excess flow to the tank. That type of reg will maintain a constant flow through the in-tank pump, keeping it cool and keeping it from burning out.
- At least you got one out of 3 right, which is acceptable in baseball. Although some have reported leaving the in-tank in and unpowered without problems, the wise course is to remove it if you aren't going to use it (use it or lose it, you know).
- To by-pass the in-tank, remove the sending unit, remove the electric pump from the sending unit, add line to extend the pick-up tube down to where the in-tank pickup was, put a pick-up strainer on it, reinstall the sending unit.
im confused on this whole deal to. to go from tbi to carb, i have a intake, carb, distributer. now, i can run the in-tank pump as long as i put a regulater with a return to get the correct amount of fuel to the carb and send the extra back to the tank? if so where do most people install that? on the driverside fender? lately i havnt been making sence of anything, so bear with me on this.
My mallory 4 port w/return looks nice, but i used braided stainless steel lines for all my fuel stuff and it was getting cluttered under the hood. I moved it to the very back. I drilled a hole from behind the back seats and put a bolt through it, so now the regulator is mounted between the backseat and the back axel. It looks really nice and its easy to setup. I only had to run 1 long line from the back to my carb. The lines from the sending unit are right above my regulator. If I need to adjust the pressure, i pull the line from my carb, stick it on the gauge and have someone read it to me while i adjust the regulator.
that's just how I did it for a few reasons. It probably isnt the best and i'm sure someone will tell me so.
Not to hijack the thread or anything but i am going to be replacing my 305 tbi with a 350 carbed motor. I am going to keep my intank fuel pump and run a 3 port return style regulator. I was wondering, once the ecm is out, how can i wire up the fuel pump so it will run?
Not to hijack the thread or anything but i am going to be replacing my 305 tbi with a 350 carbed motor. I am going to keep my intank fuel pump and run a 3 port return style regulator. I was wondering, once the ecm is out, how can i wire up the fuel pump so it will run?
Cut the Dark Green/white that goes to the fuel pump relay and connect the end of the wire that goes to the relay to an unused ignition wire such as one of the wires that provide power to the injectors. Pink is one and Pink/black is the other. Either one will work. The fuel pump will then run whenever the key is on, powered thru it's original circuit.
Get the right regulator. It's called a "bypass regulator".
Don't forget the ECM controls one fan and the TCC depending on model also.
They sell switches to control these at Jegs & Summit.
If I spray starting fluid or gas down the TBI's, it fires right up but quits in a second or 2. I can hear the intank fuel pump click and buzz when I turn on the ignition key, and a relay clicking under the hood by the driver's side. I took off the fuel filter and cranked the motor but there is no gas in the line. There is at least 5 gals of fuel in the tank. The car sat in a field without a gas cap for about 4 months, is it possible the fuel pump froze up? Also, there is no power to the fuse under the dash. Is there another fuse or fusible link in the circuit? Does this sound like a bad diaphram in the fuel pump? If so, how can I bypass the intank pump? I don't want to drop the rear end to get the tank out.
Please help!
If I spray starting fluid or gas down the TBI's, it fires right up but quits in a second or 2. I can hear the intank fuel pump click and buzz when I turn on the ignition key, and a relay clicking under the hood by the driver's side. I took off the fuel filter and cranked the motor but there is no gas in the line. There is at least 5 gals of fuel in the tank. The car sat in a field without a gas cap for about 4 months, is it possible the fuel pump froze up? Also, there is no power to the fuse under the dash. Is there another fuse or fusible link in the circuit? Does this sound like a bad diaphram in the fuel pump? If so, how can I bypass the intank pump? I don't want to drop the rear end to get the tank out.
Please help!
Had a very similar problem with my 1989 305 TBI. It turned out to be caused by the piece of rubber hose connecting the pump to the steel fuel line. It was actually dissolved in gasoline. http://img301.imageshack.us/img301/3148/Photo_0144_.jpg
As my car is not very powerful, I wasn't afraid to cut a hole in my trunk (or should I say: install a fuel door ). I had no place and no tools to drop the tank.
With our new gas formulas now, that’s not uncommon either. Recently we were having issues with a newer chevy Silverado which after a new pump install quit 4 days later, and the proper rated hose used in the same location came out looking just like that…
The regulator is all marked, just don't overtighten the lines in. I just took the regulator and lines to Brafasco and Cummins hydraulics, and they made everything I needed with all the fittings for me for like $20. Things may be a little different for you, but I just took out ALL the wiring from the passenger side, including all the wires to the ecm. The fuel pump will not work, I just wired mine to a switch that I put in the ash tray (no one ever smokes in my car, ever). This is very easy since the wiring for the fuel pump is right behind the back seat if you lift the carpet. I beleive the pink wire was power, but use a test light to make sure . The best way would be to wire to a oil pressure switch, but this way if someone steals my car they won't get very far 
). I had no place and no tools to drop the tank. 
