CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
Replacing the original TBI engine with a carbureted engine
- Thread starter JT88K5
- Start date
- Status
I will forever remember that device is a knock sensor. Many thanks for the fast response.
Planning on putting the tank back in this evening, new o ring in hand. Gonna be a couple weeks until I can get the exhaust built and fire it up. Don’t have the efi in hand yet. Pause
Planning on putting the tank back in this evening, new o ring in hand. Gonna be a couple weeks until I can get the exhaust built and fire it up. Don’t have the efi in hand yet. Pause
In my defense it set my post 45 minutes after I hit the button due to bad service. The good news is the knock sensor was still there.
When you get to doing EFI, make sure you have absolutely no exhaust leaks on the side with the oxygen sensor. The smallest of leak can get picked up by the sensor. It will change how the EFI sees to fuel the engine.
In order to get around that problem I went to a self heating 4-wire O2 sensor that is now located in the Y-pipe collector so it read both sides of the exhaust system.
Assuming that fixes the problem would be a fallacy.
It’s been proven on all of the EFI systems that you can suck oxygen as much as 2 feet from a leak back to the O2 sensor
Running long tubes since they were on it and were part of the deal. Efi Directions say to place the O2 sensor 2-10 inches after the header. Plan is to try to build a 2.5” y pipe from the headers to the 3” cat then the stock 3” parts out the back. After market cat and flow master.
I’m surprised that a small exhaust leak would be detectable that far downstream from the O2. Definitely good info to know.
Don’t have the efi in my hands yet sooo. Tossed the carb on dumped some fuel in and lit it up to test wiring and starter engagement and just because it seemed like the thing to do. I was so excited to hear it fire up, I didn’t even look at the gauges. Only ran it for 20 seconds, don’t have coolant, no strange noises. So far so good.
I’m surprised that a small exhaust leak would be detectable that far downstream from the O2. Definitely good info to know.
Don’t have the efi in my hands yet sooo. Tossed the carb on dumped some fuel in and lit it up to test wiring and starter engagement and just because it seemed like the thing to do. I was so excited to hear it fire up, I didn’t even look at the gauges. Only ran it for 20 seconds, don’t have coolant, no strange noises. So far so good.
run both carb 350 stock to tbi 350 stock . ..
i would NOT pass up a solid tbi system and free flow cat or no cat over basic carb any day .
tbi just runs and works stupid simple. newer aftermarket is nice but i sure do miss my gm tbi setup for simple stupid setup it was .
i would NOT pass up a solid tbi system and free flow cat or no cat over basic carb any day .
tbi just runs and works stupid simple. newer aftermarket is nice but i sure do miss my gm tbi setup for simple stupid setup it was .
That was going to be my reply to @Bent77. I have watched plenty of YouTube videos on an EFI install where the O2 sensor supplied with the EFI kit was installed farther down stream from the headers than 2". I can understand the logic behind the placing of the O2 sensor not being too far down stream, but brand new exhaust system like what I had built for my truck is not going to have enough of a leak to make that much difference.
Here is a picture of my exhaust system that was built by the best muffler shop in town. You can see where the 4-wire O2 sensor is installed in the Y-pipe. My exhaust system is completely custom built for 10" lift truck. It has an aftermarket Y-pipe, and a high flow aftermarket CAT with a low budget in house Jegs turbo muffler.
I quoted you because you constantly post out of date or misleading information. Then the people who are trying to get something correct make assumptionsThat was going to be my reply to @Bent77. I have watched plenty of YouTube videos on an EFI install where the O2 sensor supplied with the EFI kit was installed farther down stream from the headers than 2". I can understand the logic behind the placing of the O2 sensor not being too far down stream, but brand new exhaust system like what I had built for my truck is not going to have enough of a leak to make that much difference.
Here is a picture of my exhaust system that was built by the best muffler shop in town. You can see where the 4-wire O2 sensor is installed in the Y-pipe. My exhaust system is completely custom built for 10" lift truck. It has an aftermarket Y-pipe, and a high flow aftermarket CAT with a low budget in house Jegs turbo muffler.
A 4 wire o2 doesn’t fix exhaust leaks
It’s useful in your application because you moved it further from the collection point
This creates a need for it to be heated
In terms of leaks. Do some research. Every manufacturer of EFI has an entire page in the installation manual specifically citing o2 locations, both in terms of collection distance and leaks.
If it is useful in my application, then how is what I posted misleading?
@JT88K5 any exhaust leak up stream of the o2 is going to report bogus info to the ecm and fu bar your air fuel.
Back in the beginning 1980-81, don't mention caddie or Mercedes, check engine lights came on at certain conditions. This was caused by 02 sensors cooling off, the ecm would revert to open loop, and illuminate the cel.
GM start shielding and very careful placement, until the advent of heated o2s.
As far sensors are concerned the o2 is one of the most important, if running cats.
No cats then is just good info for a good running engine through out the engines running situations
Back in the beginning 1980-81, don't mention caddie or Mercedes, check engine lights came on at certain conditions. This was caused by 02 sensors cooling off, the ecm would revert to open loop, and illuminate the cel.
GM start shielding and very careful placement, until the advent of heated o2s.
As far sensors are concerned the o2 is one of the most important, if running cats.
No cats then is just good info for a good running engine through out the engines running situations
Correct. Even with open headers, the manufacturers have a spec for that distance, with a caveat and a warning.
The oxygen leak thing is applicable to 3 wire unheated o2 as well, with a completely new system. @6872xtc can attest to that
Don't think any o2 will read correctly with an up stream leak.
Only when there is positive pressure in the system. In conditions/locations where there are negative pressure trailing pulses, outside air is drawn in. The extra oxygen looks like you need more fuel.
I have done data logging with TunerPro on my truck, and the BLM's are pretty decent. Not perfect, but still pretty good. The only method of tuning on my truck is the adjustable fuel pressure regulator on my TBI, which runs at 12-PSI over the stock 9.5-PSI my TBI was running at before Vic Morse with Ultimate Mods package installed the adjustable fuel pressure regulator on my TBI. I would like to do chip tuning, but my 1991 V3500 came with a rare 7060 ECM/PCM that only trucks with a 4L80E trans came with from 1991 to 1996. If I burned that thing up...good luck finding another one. I am running a mild Computer Controlled Comp cam in my GM Goodwrench crate engine with only about 10,000 miles on it. This cam is mild enough to run in a TBI engine with no modifications to the ECM. The cam is a single pattern cam with only 30 degrees more duration, and 20 thousands more lift over a stock TBI cam.
The headers won’t cause much issue (leaks aside) as long as the sensor is close to the collector.
Very true.
And I had a leak so small that only one of my friends could hear it without a stethoscope. Several others and myself couldn't hear it.
But it sure screwed the fuel trims up!
To the OP, as Bent said, headers won't be a problem as long as you are leak free. I have 2 trucks with long tubes and O2 sensors now.
- Status
