I have a 70 K5 whose engine is coming out. I have three choices for its next engine. Whatever I do I'll be running an SM465 and a NP205. My choices are a TBI 350 from a 93 Suburban, a TPI 305 from an 86 Iroc, and a carbureted 350. All three are runners. The Suburban and Iroc are both mine and are still complete vehicles (with automatics). I think I'd prefer to use the TPI but I don't really have a good reason for my preference. This vehicle will be spending some time at the 7000 foot level so I'm not too wild about the carbureted engine. Also, is there a good site that covers the basics of these types of swaps. Thanks.
CK5
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Another TBI vs TPI question
- Thread starter fesser
- Start date
Hmm, not sure that I've seen a site comparing them.
Carb is going to be easiest obviously, but I'd throw any carb on the planet out the window if I had the choice of either injection systems you mention.
TBI is going to be the better bet if you plan on a larger or more powerful motor down the road. It's not as limited as TPI is by hardware...you can always go 454 throttle body and injector, and feed a decent engine pretty easily.
TPI is going to give you the best all-around driveability. Low end power can be argued all day long, since the TBI equipped vehicles never had the same cams as their TPI brethren, so any power comparison of stock numbers really isn't fair.
MAF TPI theoretically can't compensate for altitude as well as TBI. I change altitude on the order of 5000ft, I don't notice much difference, but mine isn't tuned quite right either, so any difference could be due to that.
In the end though, the 305 will be harder to "upgrade" to a 350, since there are a few specific components you'd need to replace.
Carb is going to be easiest obviously, but I'd throw any carb on the planet out the window if I had the choice of either injection systems you mention.
TBI is going to be the better bet if you plan on a larger or more powerful motor down the road. It's not as limited as TPI is by hardware...you can always go 454 throttle body and injector, and feed a decent engine pretty easily.
TPI is going to give you the best all-around driveability. Low end power can be argued all day long, since the TBI equipped vehicles never had the same cams as their TPI brethren, so any power comparison of stock numbers really isn't fair.
MAF TPI theoretically can't compensate for altitude as well as TBI. I change altitude on the order of 5000ft, I don't notice much difference, but mine isn't tuned quite right either, so any difference could be due to that.
In the end though, the 305 will be harder to "upgrade" to a 350, since there are a few specific components you'd need to replace.
Mike D
1/2 ton status
I converted my 350 from carb to TBI. It has almost been a year since the conversion and I wish I had done it sooner. The truck doesn't get used a lot ( once or twice every two weeks ) so cold starting ( with the carb ) has always been an issue. I duck & goose hunt on weekends in December and January so I never know if the truck will start. Now with TBI it starts instantly with good acceleration and overall performance.
I understand a TPI makes more power but it is a 305 and from an IROC ( much lighter than a truck ). You probably would also have a chip burnt to correctly perform in your K5.
If you go the TBI route I suggest you buy a stand alone wiring harness. You still can use all the sensors and computer from your Suburban. I obtained a wiring harness from a junk yard - what a pain in the butt - the factory wiring contains wiring for the alernator, the AC, the AT kickdown wiring and relay, etc. Most of this is useless. I spent 10 hours removing useless wiring for sensors that will not be used.
I finally broke down and purchased a harness from Howell Enginering, simple to hook up and the engine started and ran smooth instantly. Think about it.
I understand a TPI makes more power but it is a 305 and from an IROC ( much lighter than a truck ). You probably would also have a chip burnt to correctly perform in your K5.
If you go the TBI route I suggest you buy a stand alone wiring harness. You still can use all the sensors and computer from your Suburban. I obtained a wiring harness from a junk yard - what a pain in the butt - the factory wiring contains wiring for the alernator, the AC, the AT kickdown wiring and relay, etc. Most of this is useless. I spent 10 hours removing useless wiring for sensors that will not be used.
I finally broke down and purchased a harness from Howell Enginering, simple to hook up and the engine started and ran smooth instantly. Think about it.
Thunder
3/4 ton status
I would go with the TBI 350 in the Burb. More HP/Torque than the 305 IROC engine.
350 TBI has Better torque curve for a truck than a car 305. Less hassle to swap.
Why put in a little 305 when you have a 350.
350 TBI has Better torque curve for a truck than a car 305. Less hassle to swap.
Why put in a little 305 when you have a 350.
I would install the TBI engine but put the TPI intake on it and swap out the injectors for the proper sized 350 injectors. This combo will make the most torque down low where you need it. You would need to have Brian at www.TBIchips.com burn you a new chip though. Don't forget that you'll need a new electric fuel pump no matter which engine you choose (if TBI or TPI). TPI requires a high pressure pump and the TBI will accept a low (at least 20psi) or high pressure pump.
Gentlemen, I am still learning the right way to post and reply on here. If I mess up, forgive me. I think based on everyone's valuable input that I will go with the TBI 350 out of my Suburban. It was a good running engine when the tranny took a dump. I will contact Howell about a wiring harness. I also plan to steal the third seat and all the mounting hardware because they are so easy to install and remove. I am also toying with stealing the gas cap access door and mounting it flush on the K-5. I like things to look original but a tube sticking out of a fender through a big black rubber donut just doesn't work for me. I may be able to trade the TPI 305 to a guy that did metal work for me on a Chevelle for a good truck cab that he has. That will give me the windshield frame upper corners that I need. Thanks again to everyone who replied.
Why buy a harness if you already have the entire car with motor you have the wiring you need.
Why buy a harness if you already have the entire car with motor you have the wiring you need.
I was thinking of buying the harness mainly because it seemed like I'd be less likely to screw up the installation by modifying or stripping down the stock harness. I've never worked wih fuel injected setups before and still don't know what exactly needs to be salvaged from the Suburban. I was hoping it would become more evident as I pull the engine.
I was thinking of buying the harness mainly because it seemed like I'd be less likely to screw up the installation by modifying or stripping down the stock harness. I've never worked wih fuel injected setups before and still don't know what exactly needs to be salvaged from the Suburban. I was hoping it would become more evident as I pull the engine.
Wiring harness diagrams at the bottom of the page.
http://www.diy-efi.org/gmecm/ecm_info/1227747/
http://www.diy-efi.org/gmecm/ecm_info/1227747/
odin
1/2 ton status
FWIW
I converted my rig to TPI using an 86 MAF off an IROC. The engine is a Vortec headed mild roller cam with 10.0 to comp. Performance, cold start up and driveability are light years better than the carb I was running.
MAF 88-89 TPI can compensate for some engine mods (larger cam) within about 10 percent of stock, without the need for a custom PROM.
We can all argue over TBI vs TPI but the fact is TPI is mulit-port injection which has been the automotive industry standard for almost a decade now. For good reason IMHO.
I converted my rig to TPI using an 86 MAF off an IROC. The engine is a Vortec headed mild roller cam with 10.0 to comp. Performance, cold start up and driveability are light years better than the carb I was running.
MAF 88-89 TPI can compensate for some engine mods (larger cam) within about 10 percent of stock, without the need for a custom PROM.
We can all argue over TBI vs TPI but the fact is TPI is mulit-port injection which has been the automotive industry standard for almost a decade now. For good reason IMHO.
Mike D
1/2 ton status
fesser - You are wiser than your years. A Howell wiring harness will make it almost fun to hook up. The Howell harness contains about 1/3 of the wires the factory harness contains.
You would reuse the alternator, starter, and distrib wiring already existing under the hood.
You would reuse the alternator, starter, and distrib wiring already existing under the hood.
Wiring harness diagrams at the bottom of the page.
http://www.diy-efi.org/gmecm/ecm_info/1227747/
__________________
Well, I've been just a little slow on the swap, but I'm actually doing it now. One change however, my donor vehicle is an 87 Suburban with a 350. When I started I was thinking of using the 350 setup from a 93 Suburban (still here). Eagle Mark was kind enough to provide the above link with wiring diagrams. My question is...How different are the diagrams likely to be between different year TBI setups. Will the ones on the link be the same for my 87? I kept every stinking wire intact including the fuse box and light harnesses (except to the rear), so weeding out the wires I need is going to take a bit of time and I want to make sure I'm looking at the right diagram.
http://www.diy-efi.org/gmecm/ecm_info/1227747/
__________________
Well, I've been just a little slow on the swap, but I'm actually doing it now. One change however, my donor vehicle is an 87 Suburban with a 350. When I started I was thinking of using the 350 setup from a 93 Suburban (still here). Eagle Mark was kind enough to provide the above link with wiring diagrams. My question is...How different are the diagrams likely to be between different year TBI setups. Will the ones on the link be the same for my 87? I kept every stinking wire intact including the fuse box and light harnesses (except to the rear), so weeding out the wires I need is going to take a bit of time and I want to make sure I'm looking at the right diagram.
dave w
1/2 ton status
The 1227747 wiring is the same 1987 - 1992. The 1227747 has different wiring for different emissions equipment (EGR, EVRV, Hot Fuel Module, AIR Switch), manual or automatic transmission. Some 1227747 applications do not have a knock sensor, so the ESC is not wired. The important wiring is the same from 1987 - 1992, O2 Sensor, TPS, CTS, IAC, EST, MAP, Injectors, Park / Neutral Switch, Oil Pressure Switch, Crank Input, Battery +, Ignition Switch (run / start), and Fuel Pump Relay.
When I re-work a factory harness, I start with the ignition switch, ground and battery wires first. I use only two fuses, one fuse for the battery + wire, and one for the ignition switch wires. The check engine light (SES) needs power from the ignition switch when the ignition switch is in the run position and the other wire to the SES light is from the ECM. I then get the ALDL wires done. I keep the SES light near the ALDL connector, I then move to the sensor wires. Some sensors get 5 Volts from the ECM, not 12 Volts from the ignition switch.
I always have to splice / solder wires on a factory harness. I'm sure you will notice several splice / solder wires in the factory harness.Re-working a factory harness is a real pain the first time.
dave w
Okay. So here's a goofy idea.... since my 70 k5 has very little wiring compared to the 87 burb, should I consider replacing all the 70 k5 wiring with the complete 87 harness? I've been toying with replacing the gauge/speedo cluster with aftermarket gauges anyway. I kept all of the wiring and the steering column from the 87.
dave w
1/2 ton status
It's option that would up to the vehicle owner. It's many hours of labor to transplant the 87 harness into the 70 K5. I think it's less hours of labor to re-work the TBI wiring harness.
dave w
Now that would be a TON of work! Stripping the EFI section of a harness is easy. I can pull one from a truck and install it, work through one wire at a time and be done in a few hours. Saves $300 to $400 on a new harness. But some people have more money then time!
