55.2-59 91 Chevy 350. Keep efi/ throttle body vs. carb

[Bridgeman57]

Picking up a 91 350 with 163k original miles. Stock engine. 4L60 tranny for $500. It will be going into a 57 Chevy 3600 thats converted to 4x4. Not sure to keep it fuel injected or swap to carb. Is it a pretty simple swap? Just manifold, carb, fuel reg and other little things? I know fuel injection has its benefits. It comes with the whole computer and harness. Also should I use the 4L60 or toss it and get a tb350 or 400?
Thanks, anything helps

[joedoh]

running? keep it for sure

if not running, you might spend a little on parts to fix it, usually need a fuel pump and injectors and TBI rebuild kit which is just a bunch of gaskets.

1991 TBI harness is pretty well standalone, lots of info on the web for hooking it up in a chassis. you will need an electric pump capable of about 12 psi

keeping the 4l60 (the 91 is not an "e", you are right) will give you overdrive, which is the benefit over a TH350. I am guessing you have a divorced transfer case, make sure the extra length of the 4l60 will fit.

[Bridgeman57]

Yeah running, seems like great engine. He says tranny slips a little bit. So it will probably last awhile. I have a np203, looking for a 205. Thanks for the heads up👍🏻 Easy pulling it all out. Putting the harness back together in another truck is what I’m worried about

[mongocanfly]

You'll need one of those nice shiny adapters to hang a 203/205 behind a 4l60, ..
http://67-72chevytrucks.com/vboard/s....php?p=3697343
Unless like what Russ said and you have a divorced tc
Or find a 700r4 4wd trans....you can also use a t350/400 as well...need to factor in tire size and axle ratios

[mr48chev]

If you are going to use the truck as a real 4x4 the FI doesn't care what angle you have the truck at going up a grade, down a grade or sideways it still works the same.

As Joedoe implied if it comes with all the pieces and wiring that is little added expense except a fuel pump. Even swapping to a carb you will need an electric fuel pump on that engine. plus if you don't have a carb that is in good shape and an intake that bolts to that engine that fits the carb that could be a 500 buck hit before you ever fire it up.

Trans that slips= rebuild it or sell it as a core to be rebuilt. Again do you already have one that is in good shape that works with the transfer? A divorced transfer usually just means a bit of a change to the drive shaft from trans to transfer with few other mods. a dedicated transfer means having the right adapter and if the od trans was 2 wheel drive swapping the output shaft in most cases.

Still it is build the best and most drivable truck you can without just standing back and throwing money at it.

[Dan in Pasadena]

Electronic feel injection versus a carburetor? This is a hard decision?

OF COURSE EFI. Leaps and bounds better than a carb.

[1project2many]

Another vote for EFI. The TBI systems are super reliable. They're so good that when a rust belt truck is little more than a pile of rust the owner often laments "It's a shame to junk it. It runs so good!"

I put Crossfire TBI into mine in '94 or '95 and it still runs well.

[mick53]

Originally Posted by 1project2many

Another vote for EFI. The TBI systems are super reliable. They're so good that when a rust belt truck is little more than a pile of rust the owner often laments "It's a shame to junk it. It runs so good!"

I put Crossfire TBI into mine in '94 or '95 and it still runs well.

i say EFI on a 4X4 but carbs still make more power. Sorry guys.

[MiraclePieCo]

Do you like dealing with Check Engine lights and a truck that won't run if even ONE sensor fails? Do you like being able to do roadside repairs, or prefer to take it to a shop with sophisticated diagnostic equipment for every little hiccup? Do you like having tons of extra wiring, sensors, and an EFI harness that adds complexity and associated failures? TBI was a pollution solution, had nothing to do with performance. Simplicity is a blessing. I've seen my last Check Engine light. Carbs run no matter what.

[joedoh]

Originally Posted by Bridgeman57

Putting the harness back together in another truck is what I’m worried about

the same guys that sell LS harnesses will also sell a TBI harness that is pared down to 4 wires. although you can find the how-to on doing it yourself online. buying one will still cost less than the intake/carb/distributor you need to convert it to carb,

Originally Posted by MiraclePieCo

Do you like dealing with Check Engine lights and a truck that won't run if even ONE sensor fails? Do you like being able to do roadside repairs, or prefer to take it to a shop with sophisticated diagnostic equipment for every little hiccup? Do you like having tons of extra wiring, sensors, and an EFI harness that adds complexity and associated failures? TBI was a pollution solution, had nothing to do with performance. Simplicity is a blessing. I've seen my last Check Engine light. Carbs run no matter what.

i think you might be a little over dramatic here, your current truck has been broken more times and inert for longer than anything with EFI/OBD I have owned in the last 25 years (which has been zero times, by the way, 3 CPI trucks, 1 SFI truck, 2 TBI trucks, and a daily LQ4 with 180k).

[dsraven]

I know it's a dodge big block but here is a dyno test of the aftermarket fuel injection vs carb. a bit long winded but a good demo for the efi vs carb.
me?, efi. not out to smoke the tires, just want easy starts, reliability at different altitudes and less exhaust stink.
to each their own.
https://www.youtube.com/watch?v=3Zj0RMPKquw

[1project2many]

Do you like dealing with Check Engine lights and a truck that won't run if even ONE sensor fails? Do you like being able to do roadside repairs, or prefer to take it to a shop with sophisticated diagnostic equipment for every little hiccup? Do you like having tons of extra wiring, sensors, and an EFI harness that adds complexity and associated failures? TBI was a pollution solution, had nothing to do with performance. Simplicity is a blessing. I've seen my last Check Engine light. Carbs run no matter what.

Huh? Sophisticated diagnostic equipment? The ecm on a '91 350 is pretty basic stuff. You can read trouble codes with a paperclip! Most of the diagnostic tests for that ecm are available in "no scan tool available" format which uses a DVOM and simple observation testing to complete a diagnosis. The computers are programmed to run with five sensors (throttle position, coolant temperature, knock sensor, crank rotation, and vehicle speed) and the engine will usually run with any but the crank rotation sensor failed. It sounds like you don't want to learn about computerized systems, but the OBDI vehicles really aren't that bad. Now if the choice was with a late model OBDII vehicle you might get more agreement.

i say EFI on a 4X4 but carbs still make more power. Sorry guys.

But more airflow plus more fuel is really what makes more power. How how it's delivered is often less important than what's available. GM TBI systems are designed for V8 engines making less than 300 hp which is a very different world than an engine making 200+ hp/liter.

What EFI does that a carb can't do is provide for better fuel control over a wider range of conditions. And when you add computer controlled spark you improve the odds even more. Consider that computeized can add fuel or spark at one rpm range, reduce it at a higher range, then add it again as needed and you'll realize that's a hard combination to match with old-fashioned carb and distributor.

I think about it this way: Once upon a time getting into a 10 second drag car usually meant getting into a vehicle that was barely streetable. No cold weather compensation, no hot temp compensation, crazy cam needing crazy high idle and high stall converters. These days you can drive your ten second car to and from the track then cruise with it on the weekends after heading downtown to get groceries.

[Bridgeman57]

Thanks a lot. Going to stick with efi. But the tranny, 4L60 is 2wd. I need to convert it to 4x4. Is it worth doing or just find one that’s 4x4. I would like to just swap with a tb350/400 but idk how that would work with the computer from the 91. Anybody dealt with a newer motor and older tranny?

[joedoh]

Originally Posted by Bridgeman57

Thanks a lot. Going to stick with efi. But the tranny, 4L60 is 2wd. I need to convert it to 4x4. Is it worth doing or just find one that’s 4x4. I would like to just swap with a tb350/400 but idk how that would work with the computer from the 91. Anybody dealt with a newer motor and older tranny?

the4l60 in 1991 is not electronic (except the speedo) so there is a kickdown cable on the tbi and a lockup switch that i think runs through your brake wiring. no issues switching it to any other trans EXCEPT a 4l60e, you dont have the controller with your stuff.

needing overdrive is really about your rear gear. if you have a numerically low gear a th350 or th400 will do fine. also, look at your tire size, bigger tires lower gear ratio.

[mgchevyparts]

My 2019 Silverado LTZ has a computer, my 59 Chevy 3100 does not and that's the way I like it.

[1project2many]

To build on what joedoh said, this was a common swap in the '80s and early '90s. The medium shaft THM 350 and the 700R4 (comon name for non-electronic version of 4L60E) are almost the same length. They use the same output shaft which means you won't have to change the driveshaft or yoke. The shifter for a 700 will fit a 350 (although the gears don't always match up). And generally speaking a stock 350 is more durable than a stock 700. Some differences to note: The 700R4 uses a computer controlled torque converter clutch which is not found on most THM 350/400 transmissions. Disconnecting the tcc can cause the ecm to set trouble codes. The solution is to use a manual transmission calibration or to use a custom chip. The cooler lines are in a slightly different location. The solution is to reshape the lines or replace them. The rear mount is located farther back than the 350 mount. The solution is to fabricate a custom mount or crossmember. The 700 throttle valve cable uses a different geometry at the throttle body attaching point than the thm350 detent cable. The solution is to determine a new pin location and move it on the throttle linkage. And finally the 700 uses a different vehicle speed sensor. To solve this problem you will need to use a two pulse per mile "reed type" VSS and connect it to the "optical VSS" pin (probably A10) at the ecm.

If you decide to use a "short shaft" THM 400 you will need a driveshaft yoke, connect a kickdown switch, and (again) deal with the tcc codes.

Both can work but it may be easier to use the 700.

[MiraclePieCo]

Originally Posted by joedoh

i think you might be a little over dramatic here, your current truck has been broken more times and inert for longer than anything with EFI/OBD I have owned in the last 25 years (which has been zero times, by the way, 3 CPI trucks, 1 SFI truck, 2 TBI trucks, and a daily LQ4 with 180k).

WHaaa? I think you're mistaken. My truck has been on the road two years and has never been broken. I had a cracked head I had to replace, but that was unrelated to the carb. Any other times my truck has been inoperative is for upgrades and improvements rather than repairs. I believe you're thinking of someone else. All I know is that I've had far more trouble with TBI systems than carbs - failed O2 sensor, TP sensor signal break, main ECU failure, sluggish starts because there's no accelerator pump, erratic idle speed issues that never could be rectified, etc etc. Towed in more than once with TBI issues. Once the system goes out of loop it will stop dead. Carbs might run rich, lean or inefficiently but they'll always get you there.

And dude, this is a discussion over induction systems - you sure as hell don't need to make it personal.

[joedoh]

Originally Posted by MiraclePieCo

I believe you're thinking of someone else.
And dude, this is a discussion over induction systems - you sure as hell don't need to make it personal.

could be someone else. if you took it personal you might be a little overdramatic with the doom and gloom about tbi/efi. I dont take any offense to it though.

[Bridgeman57]

Originally Posted by joedoh

the4l60 in 1991 is not electronic (except the speedo) so there is a kickdown cable on the tbi and a lockup switch that i think runs through your brake wiring. no issues switching it to any other trans EXCEPT a 4l60e, you dont have the controller with your stuff.

needing overdrive is really about your rear gear. if you have a numerically low gear a th350 or th400 will do fine. also, look at your tire size, bigger tires lower gear ratio.

Both front and rear diffs have 11:41-3.73 gears. Currently have 31in tires, 17in rims. Hopefully this 1991 350 motor will be strong enough 🤟🏻

[MiraclePieCo]

Originally Posted by 1project2many

Huh? Sophisticated diagnostic equipment? The ecm on a '91 350 is pretty basic stuff. You can read trouble codes with a paperclip! Most of the diagnostic tests for that ecm are available in "no scan tool available" format which uses a DVOM and simple observation testing to complete a diagnosis. The computers are programmed to run with five sensors (throttle position, coolant temperature, knock sensor, crank rotation, and vehicle speed) and the engine will usually run with any but the crank rotation sensor failed. It sounds like you don't want to learn about computerized systems, but the OBDI vehicles really aren't that bad.

I've learned the hard way about EFI systems. I learned from my local Chevy dealer that a simple idle adjustment can't be accomplished with a screwdriver, but must be a dealer service item at $150. I learned that each of those sensors you mentioned (and their associated wiring) is another opportunity for failure and sitting on the roadside in a Wyoming winter (a TBI car may run with a failed O2 sensor, but mine wouldn't go over 35 mph). I learned that ECMs fail totally with no warning whatsoever, and in the most dangerous of places. All my negativity against EFI is hard-learned from experience. It's an inter-related system; if one component goes out, it all fails. As my Chevy dealer mechanic says about EFI, "It's nice...when it works."

[Bridgeman57]

Originally Posted by 1project2many

To build on what joedoh said, this was a common swap in the '80s and early '90s. The medium shaft THM 350 and the 700R4 (comon name for non-electronic version of 4L60E) are almost the same length. They use the same output shaft which means you won't have to change the driveshaft or yoke. The shifter for a 700 will fit a 350 (although the gears don't always match up). And generally speaking a stock 350 is more durable than a stock 700. Some differences to note: The 700R4 uses a computer controlled torque converter clutch which is not found on most THM 350/400 transmissions. Disconnecting the tcc can cause the ecm to set trouble codes. The solution is to use a manual transmission calibration or to use a custom chip. The cooler lines are in a slightly different location. The solution is to reshape the lines or replace them. The rear mount is located farther back than the 350 mount. The solution is to fabricate a custom mount or crossmember. The 700 throttle valve cable uses a different geometry at the throttle body attaching point than the thm350 detent cable. The solution is to determine a new pin location and move it on the throttle linkage. And finally the 700 uses a different vehicle speed sensor. To solve this problem you will need to use a two pulse per mile "reed type" VSS and connect it to the "optical VSS" pin (probably A10) at the ecm.

If you decide to use a "short shaft" THM 400 you will need a driveshaft yoke, connect a kickdown switch, and (again) deal with the tcc codes.

Both can work but it may be easier to use the 700.

Yes sir thank you, sticking with the 4L60 sounds less complicated haha. I appreciate your time. I will have more questions real soon. 🤟🏻

[mick53]

Originally Posted by 1project2many

Huh? Sophisticated diagnostic equipment? The ecm on a '91 350 is pretty basic stuff. You can read trouble codes with a paperclip! Most of the diagnostic tests for that ecm are available in "no scan tool available" format which uses a DVOM and simple observation testing to complete a diagnosis. The computers are programmed to run with five sensors (throttle position, coolant temperature, knock sensor, crank rotation, and vehicle speed) and the engine will usually run with any but the crank rotation sensor failed. It sounds like you don't want to learn about computerized systems, but the OBDI vehicles really aren't that bad. Now if the choice was with a late model OBDII vehicle you might get more agreement.



But more airflow plus more fuel is really what makes more power. How how it's delivered is often less important than what's available. GM TBI systems are designed for V8 engines making less than 300 hp which is a very different world than an engine making 200+ hp/liter.

What EFI does that a carb can't do is provide for better fuel control over a wider range of conditions. And when you add computer controlled spark you improve the odds even more. Consider that computeized can add fuel or spark at one rpm range, reduce it at a higher range, then add it again as needed and you'll realize that's a hard combination to match with old-fashioned carb and distributor.

I think about it this way: Once upon a time getting into a 10 second drag car usually meant getting into a vehicle that was barely streetable. No cold weather compensation, no hot temp compensation, crazy cam needing crazy high idle and high stall converters. These days you can drive your ten second car to and from the track then cruise with it on the weekends after heading downtown to get groceries.

I'm all over the place on my 53 3100. I'm building a 292. Billet crank and solid roller cam. The first of it's kind 12 port cross flow head from New Zealand. 4-71 blower and 3 Roch. 2 bbl's. 5 stage dry sump oil system. Then I kind of crossed over with an Electromotive Tech S200 direct fire ignition. Duel fuel system. Also electric P/S and A/C. Then I return to my roots with a TKO 600 5 speed and a Frankland quick change rear end with leaf springs. Bicknel torque arm.

[joedoh]

good googly moogly I think you will need a kohler sink to feed that haha

[1project2many]

As my Chevy dealer mechanic says about EFI, "It's nice...when it works."

It sounds like you've had some hard luck and I can't blame you for not trusting the system. But when did these problems occur? They sound like issues from the early to mid 80s. Computers failing "without notice" was usually loose solder joints inside the computer. O2 preventing acceleration is not a common failure.

I lived in eastern MT for six years and worked at a Chevy dealer most of the time. We really didn't have too many problems with the TBI equipped trucks and I promise I would know... the ranchers all had my home # as I worked on their equipment on weekends.

I will say it was interesting to see what happened on the early TBI truck when the temp was -40F. They were only programmed to register -34f so they'd set a code for coolant temperature sensor error. And they usually wouldn't start at that temp, either. Then again, neither would the carby vehicles without a block heater.

Hmm... maybe you should stick to carbs.