Chevy Carb To Tbi

What is the most frugal way to get the right amount of fuel in a Chevy? I'm darn tired of messing with rods and jets.

I have a non vortec 4.3 with flat tappets and about 19" vac at idle
I'm not looking for max horses but I do want cruise control (pto governor), altitude compensation, stupid simplicity and reliability.

I beleave a early tbi 4.3 setup should work but I don't know how much cam they will take or really what is involved on the program side when it gets on my manual trans long block.

Would the stock pcm be the easiest and cheapest way to go? Or would something else be a better way to go?

 

As long as the cam is not overly aggressive the stock PCM should be be able to compensate for it using the O2 sensor for feedback. You will need the following sensors are well as the TBI. Air intake temp, Coolant temp, O2, Throttle position, Manifold Air Preasure, and I am sure I am missing something.

I used a GM TBI to convert my 258. But, I used a Megasquirt for the PCM and custom wired the jeep. I was geared at 91:1 in low range. It would idle down to about 300RPM on a climb without touching the gas and crawl just about anything.

 

that's the line I've seen on most threads. The cam had a note "not for fuel injected engines" I know that likely a disclaimer incase someone gets upset when they put it in there highly modified truck.
Anywho this is what I got, all I know is it has a nice blend of lug-a-dub and whapa.

20160116_163903 by Joe with a jeep, on Flickr

 

I would think that the cam shouldn't matter. My TBI motor is a 95' using a OBDI computer. It has a map sensor, two coolant sensors (one in the intake, one in the drivers head.) and two knock sensors. (one in each head.) There's also a EGR Solenoid and a Vehicle Speed Sensor. Heated O2 Sensor, Throttle Position Sensor, and a Idle Air Control.

 

One last thing. You will need to replace your fuel pump and run a return line from the TBI to the tank. I was able to source a decent inline electric one for not a lot of $$ and mounted it on the inside of the frame rail. The pressure valve on the Throttle body will bypass anything above a certain PSI and it needs a return path to the tank.

 

Alrighty I scoped out the local yard and the only tbi 4.3s were these two.

20200806_112101 by Joe with a jeep, on Flickr

20200806_112358 by Joe with a jeep, on Flickr

I'm thinking the truck would be a better donor for miscellaneous stuff but, I really want to avoid 2nd hand problems and the junkyard has no idea what stuff is worth they were wanting $20 for a sensor one guy was looking at. I'm thinking the computer throttle body and harness will be the critical items.

Good news is I have approval to spend $400. I threw out a number and I feel it's too low.

 

Easier to run a Sniper? Not the cheapest but prolly the easiest.

 

It was a tough sell for the low estimate $400 price of tbi.

@scott milliner @hudsonhawk
Can I reuse my hei distributor or do I need to get all of that to use the gm pcm?

 

My Distributor has 6 wire coming out of it.

 

If you want to use the GM PROM for the 4.3, I expect you'll need to keep the whole package, like spark control and knock sensor. I believe you can reprogram the ECU, making the system fuel-only. Then you can use any ignition you want. This is what Howell sells. Another option is to use a Megasquirt computer with the 4.3L Rochester throttle body. The Megasquirt holds the Air-Fuel table in CPU memory and you can program anything you want. If you check the MS-Extra board, somebody there may have already set up a 4.3L for fuel only and you could get their table.

You can buy pre-assembled Megasquirt boards, but it will be hard to come in under your $400 target. You'll still need a throttle body, some sensors, relays, fuel pump and connecting wiring.

JMO - I think unless you find a complete 4.3L TBI donor for under $400, it's going to be very difficult to complete around your $400 target. Realize that the GM cars use an in-tank fuel pump, and you'll need some form of work-alike for your Jeep.

Megasquirt 1 is the cheapest, but the CPU is out of production and the kit will end when they are gone. (Also! I recall this board has no support for the Rochester idle air stepper motor.)
MegaSquirt-I Programmable EFI System PCB2.2 - Kit w/ BLACK CASE
Megasquirt 2 comes in pretty close to your target. Not much room for other parts. And you still have to buy all the other stuff that goes with it.
MegaSquirt-II Programmable EFI System PCB3.0 - Kit w/ BLACK CASE

I think the only conceivable way to do this for something like $400 is to find a 4.3L TBI donor private-party.

Even the pick-and-pull is going to squeeze you for every little piece you need. Junk yards owners are a very contrary lot ... maybe you'll get a deal, but you'll have to dicker and be ready to walk away.

Good rule of thumb would be to decide how long you are willing to search. For the first 40% of your search, just shop, don't buy. This will give you an idea of what's possible. Then set a price and take the first best opportunity that comes along.

 

It might be possible to come in under $400 if you are totally savvy about what you are doing. Look here - Affordable DIY Fuel Injection for your IH - The Articles - note that this is an OLD thread and uses the soon-unavailable Megasquirt 1. There are two CFI throttle bodies out there, one for the 5.0L used here and one for the 3.8L V6. The V6 TB might work for your 4.3L, but you might have to fit larger injectors. Injectors are not cheap. The advantage of the CFI throttle bodies is no one uses them for conversions, instead preferring the Rochester throttle bodies from GM cars. The Megasquirt 1 will not work with the Rochester, since there is no support for the idle air stepper motor. If you are really pinching pennies, you'll have to compensate with a lot more homework and searching.

 

I am not as worried about being strict to the $400 but it's gotta be justified. I've pinched pennies for a long time on my jeep and this project is not one I want to do with a bunch of rework because something gave up the ghost. I'll take some heat but I think $600 might not be the end of me. I just need to make sure it runs well.

I really want cruise control and remote start in the future. I haven't seen that in megasquirt. maybe I haven't dived deep enough, but that and air conditioning are what drove me toward the gm computer over megasquirt.

In the 15 years I've owned this rig it's only had a reliable Carburetor for 3 years. I want something that I can get setup and forget about. No worries about e-10 or altitude, something my wife or dog can start.

 

I ran 1987/88 gm efi On my 1962 198. Ran great. The donor vehicle you want is an untouched 87 or 88 chevrolet or gmc van full. Harvest the Throttle body, the full harness and all sensors, follow the harness all the way behind the driver seat, the ecm is located in side panel behind the drivers seat. The computor is a 1227747. It is easily modified to accept programmable chips, it will accept a chip from a stock 4.3. I generated a whole book full of info about the conversion I did on my Willys. Don’t know about the cam.

 

This agrees with what I'm reading. I haven't seen any full size Vans locally, that car and truck are all that's available. There is a scrapyard in town so not much is sacred. A 30 year old under powered van just isn't to be found. I can order a refurbished pcm from rock auto for $50. I have a shopping list going on rockauto as they give the pigtail part numbers and I might just make the harness if needed I've got a feeling that the local junk yard will value this stuff higher than I agree with or I simply won't be able to get back out there for another few weeks.

Good news for those following is I already have o2 bungs on the exhaust near the manifolds on both sides. I have a spare quadrajet intake to mock up onto, I just need to find some extra daylight. The truck seems easier to find info on so I'll start with it first.

 

The efi system is the identical on the 350 as it is on the 4.3, just a chip change.What I ran into with other vehicles was that the harness couldn’t be Harvested without cutting it up. Taking it out of a van it will be in one piece, all you have to is remove the wires not needed and trim the rest to length, you will even have the grommet you need to go thru the firewall. Are you going to run a VSS?

 

I'm sure a 350 will have different injectors than a 4.3L. The throttle body will be the same, and you can swap in the 4.3L injectors, but injectors are not cheap. The chip will expect a specific fuel delivery rate that's dependent on the injector type.

Go to page 2 here Fuel Injector information Specifications specs guide to find a table of Rochester injectors.

If I found a 4.3L donor car, truck or van in the right price range, I'd snap it up. Having the harness intact would be nice, but I can cut and splice a lot of wires for the time and money invested waiting for the perfect donor to come along.

 

Tim you’re right, the injector is different, I have sourced injectors from junk yards cheap and not had problems, jw60, I checked inventory at muncie u pull in kansas city, they have a van there, might be worth calling and see if its intact and what they want for full efi?

 

I think I have a plan.
Since I don't seem to have any "free" time... kids, covid, life.
And I don't want to fuss around in the heat.
I think I'll do this one part at a time
I'm going to start listing parts and links. Please shout out if I miss anything or pick a wrong item.

First I figure this will cost less than me buying color coordinated wires and pigtails:

Engine Wiring Harness For 1988-1995 Chevy C1500 1990 1993 1992 1994 1989 N558XJ | eBay

 

Pretty sure what you see in the picture is all you get with that purchase.

"Notes: Ignition Wiring Harness; Plug-In; MSD To GM Dual Connector Coil"

 

Just a thought....... $265

TBI Wiring Harness – Affordable Fuel Injection



Or the kit starts ad $695

CHEVROLET Legacy Complete TBI Kit – Affordable Fuel Injection