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!
hey guys i just pickd up an 88 iroc and the wiring harness melted on it. it is a v8 305 TBI setup. should i purchase another harness or should i just go carb? i am soo stuck on what to do. soo wat do u guys say? stay TBI or go CARB?
This ad is not displayed to registered members. Register your free account today and become a member on ThirdGen!
__________________ 88 IROC-Z
V8 305 TBI
Projection 670CFM TB
Hedman 1 5/8" headers W/ 3" Y
Straight pipe to Flowmaster 80 Series
B&M Short Shifter
T-5 Tranny W/ Spec stage 2 clutch kit
Sponsored Links
Registered users do not see this ad. Click here to register for free!
hey guys i just pickd up an 88 iroc and the wiring harness melted on it. it is a v8 305 TBI setup. should i purchase another harness or should i just go carb? i am soo stuck on what to do. soo wat do u guys say? stay TBI or go CARB?
What are the long term goals, daily driver, or street/strip car? If you're hell bent on mileage, fix the TBI, it can be made to perform well, and will offer better mileage than most carb setups with all but the best tune on them. If its just a toy car, and you intend to mod it up, a carb may be more adaptable as you change and add modifications. Or, you can plan on investing in prom tuning equipment. Like Five7 said, make it a small double-pumper if you go with a carb. You'll need a fuel pressure regulator, and a vacuum advance distributor as well if going carb, because the computer won't properly control the timing if the TBI isn't there, and a fuel pressure regulator to bring the electric fuel pumps pressure to something more carb-friendly.
The harness just takes time to install, but its all plug and play, unless you've got some ugly hacks to deal with.
hey guys, thanx for sum info. it will be a daily driver/ play toy. i wanna do headers exhaust, cam, rear gears. i already got msd ignition distributor, wires. also have a stage 2 clutch on the way. if i do decide to go carb. do i have to change the fuel lines? and the fuel pump? thanx
Why mechanical secondaries with manual transmission:
With a T5 transmission, you need to back off the throttle during shifts (speed shifting is sure death for a T5). With a secondary air valve type carb, like q-jet or Edelbrock Performer, the air valve will close when you let off the throttle, and will be delayed opening again when you get back on it.
With a vacuum secondary carb like Holley or Demon, it's even worse - when you back off the throttle, there is a delay closing the secondaries, and then a delay opening them again when you get back on it.
With mechanical secondaries, the throttle responds instantly to the accelerator pedal.
The TBI also instantly responds to the pedal.
I'll have to bone up whether you can use an MSD distributor (non-mechanical advance type) with EFI. With some wire changes, you probably can. But, there wouldn't be any advantage over a stock distributor in good operating condition.
If your MSD distributor is mechanical/vacuum advance, you can't use it with TBI. You could use it with carb, but your list is short the intake manifold, carb, and regulator, which will be a lot more than the cost of the harness you were quoted.
There is a tech article linked from the thirdgen.org homepage about converting from EFI to carb. I believe it is missing the detail about the fuel pressure regulator, but the rest of the info you're looking for is there.
yes i have read that article, but i really am confused on it. sum peeps say i have to change the fuel pump and lines. sum say other stuff. i have pickd up the msd p/n 8360 distributor. if this cannot work with TBI i wll be going carb deffinitly. because i want great timing and have all these parts. but if i do go carb i just wanna make sure wat parts i deff need. and wat needs to be changed. because i think it will be an easier job just to go carb then try to play with this harness.
The 8360 is the vacuum/mechanical advance version. It will be less accurate than a stock EFI distributor.
I see the tech article does cover the return-style regulator. Note it says "either/or". If you keep the in-tank electric pump, you must use the regulator with the return line. If you don't use the in-tank electric pump, you must remove it. It is theoretically possible to use the in-tank electric pump with a return-type mechanical pump, but I don't recall hearing anyone who has actually done it.
Personally, I think it would be easier to replace the harness. Not only will you have to make custom harness changes to go carb, you'll also have to do all the mechanical parts changes, and fuel line changes. The harness will basically be unplug one and plug in the other (unless other nonsense has been perpetrated on the poor car).
sooo is that distributor that i got good or bad? is it worth putting in my car or no?
It is a good distributor to use with a carburetor (I have one on the 396).
It is no better than a factory electronic computer controlled ignition distributor for ignition control (assuming a basically stock EFI engine, and/or the module and coil have been replaced with upgrade aftermarket parts).
Well, I've been trying to tell you not to use that distributor with TBI. Mechanical advance is no way as accurate at electronic advance, and isn't needed with it. If you think you need an aftermarket distributor, get one for computer control. It'll hook right into your stock harness. With that and a matching coil, you won't have any need for the MSD 6A.
If you go carb'd, then go ahead and use all the MSD stuff you have.
I would just go carb but if you wanna play a bit, but it will be funner in a 350 . And also a TBI to carb swap can be pricey depending on the parts you use. I have a 74' Q-jet in great condition for $150 canadian, pm me if you want it.
well i kno it will be pricey, but i wanna know is it worth going to carb? and what parts that are on the car that need to be changed. thats what i need to know. i rather go carb but i was told it wouldnt show much improvement
It would definatley show improvement, the stock tbi unit flows like sh*t. But you will lose gas mileage. And im not sure about the laws in NY but where im from we dont have any smog laws or whatever so it doesnt really matter also our gas is very cheap. If you want a fast fun car junk that 305 and get a 350. and if you decide to keep the 305 then just repair it the cheapest way you can becuase its a waste of time modifying it.
hwo much will a 350 cost me thats complete and running? i have a freind who knows more then me and can help with install. but how much am i looking at a 350??
from my experience one thing about carbs to consider is that fo a daily driver when comparing a carb to TPI and TBI, carbs take longer to warm up on a cold winter day. it's a noticable difference
i have searched and searchd and searchd. i am still confused about this and need sum advice thats all. plus a little help on installing and changing things
Stock GM HEI ignition is as good as about any aftermarket ignition, with possible exception of something like full-race dual magneto, which is useless on the street anyway. With the TBI system and it's ignition system, spark is controlled to within 0.1 degree. Do that with ANY mechanical dist !
A carb depends on vacuum to pull gas into the air stream and mix it at the throttle blades. You can not "control" a carb with precision, but only generally, getting precision at only a few RPM/vacuum/pedal combinations.
TBI sits in the same place as a carb. It mixes gas with air at the throttle plates like a carb, but the TBI can run sideways, upside down, whatever, and fuel is precisely controlled at each and every RPM within about 12.5 RPM, and vacuum within a kPa or so, plus throttle position, not only where the pedal is, but whether or not it's moving, AND how fast, pump shot ( if needed at THAT moment ) automagicly adjusts for weather, altitude, humidity, etc. etc. etc. etc.
About the only reason to go carb, would be that you don't want to REALLY be able to tune the engine, or you want to have to retune it every time the weather changes, or you just like getting lower overall performance.
Most of us who have been fiddling with carbs for 100 years or so are glad they're gone.
In your case, you should throw the few dollars for a harness and be done with it.
i just htink if u go carb u have a better flowing manifold, better ignition, and timing. so i would say better performance. do u guys agree? or am i like thinking wrong?
i just htink if u go carb u have a better flowing manifold, better ignition, and timing. so i would say better performance. do u guys agree? or am i like thinking wrong?
Sounds to me like you're looking for justification to go with 1930's technology, mostly because you want to.
If true, then you should, because you won't be happy otherwise.
Some guys like carbs. I see 'em in my rear view all the time.
Ive never seen a tbi over 350hp NA without major major tuning and modifications. If tbi is sooo good then why is carburation the most popular way of fuel induction? when i flip through magazines like CHP why do i never see anything about tbi?? is it becuase they are so fantastic that they dont put them in there or something? am i missing something becuase last time i drove a vehicle with TBI i wanted to shoot myself. it sounds like you got a big tea kettle under your hood too with that stupid whistle TBI's make
i agree with creepingdeath, i mean if u cahnge the intake manifold, distributor, and put in msd ignition doesnt that make the car better? and will run nicer than a stock TBI setup? i just dont get it
I had a tbi on a small 85 4-cyl chevy & that for what it was, that car ran forever & ran right too, but carbs are fun to play with & I agree that with effort & expertise, some awesome results can be obtained with carbs. so perhaps it's gas n go tbi with very nice results on a 305, or if you got some time then its upgrade to carb n parts with parts that are upgradeable to 350 short block
Ive never seen a tbi over 350hp NA without major major tuning and modifications. If tbi is sooo good then why is carburation the most popular way of fuel induction?
When was the last time you looked at new cars, or any car or truck from the last several years ?
True, TBI is pretty much obsolete, just like the carb and mechanical distributors it made obsolete. Progress is progress.
But you do with what you got. If you want the best it can be, then buy new. If you want the best you can do with what you already got, then learn to tune that.
If you want to fool around with antique technology, then do that.
Cheers........
. And also a TBI to carb swap can be pricey depending on the parts you use. I have a 74' Q-jet in great condition for $150 canadian, pm me if you want it. 
