Piece together TBI set up or go carb?

[nvrenuf]

I've got a decently built, carb'd 454 that, like everybody, I'd like to convert to fuel injection but, like everybody, I haven't had the money for a kit.

I have a ('90) 454 throttle body and computer and a little research suggests that I may be able to complete this with a $325 Howell harness and $150 custom chip (+ sensors).

That said, is tbi worth it? With so many fancy kits on the market most folks frown at tbi but surely it's better than a carb, right? Some local folks have suggested that tbi is too restrictive and say I'd better just as well off with a nice SMI or Jet q-jet. Could this be right? Doesn't seem possible to me.

Motor specs;
454
Unmodified 781 heads (2.06, 1.72 valves)
Edelbrock Performer intake
~9.4 comp
Hyd roller cam (.566, 215 @ .050, 110 cl)
Shorty headers, single 3" exhaust
MSD distributor, 6al box and coil

I'm inclined to get the harness and chip without ignition and use my MSD parts however it was also suggested using the tbi ESC would be a superior option. Really?

I'm tbi illiterate and appreciate any advice you guys have on this. I have more questions but lets get thru this post first.

 

[4xcrazy]

I personally prefer a TBI over carb any day, but, after switching over to fuel injection, from dealing and learning with carb'd engines, you'll want to get all smarted up on the workings and specs of the fuel injection setup.

I'm currently fighting a major issue with mine, even after owning it for almost 10 years now, thought I had done enough research on it and knew what everything does and how it works, but being intermittent, its a teasing thing.

Next on my list of things to replace, and I'm glad you posted up the name of the company, is a new wiring harness and computer with new chip. After that, if this thing is still having issues, I will be completely lost.

to answer your question, with my opinion, I'd go fuel injection, it's a cheaper form of injection, reliable starting, especially in colder weather and a bit better fuel mileage with it's more managed fuel metering.

 

[nvrenuf]

Yeah, I couldn't see any way a carb would be better. I swear avoiding cold start irritability alone would be worth the price of the upgrade.

You're right about the learning curve, I need to find a "TBI For Dummies" book.

 

[Mastiff]

I'd stick with the carb until it gives you trouble in some way. I know I'm in the minority, but I found the TBI conversion to be a huge learning curve and pain in the ass. My truck ran badly for years while I worked through bugs and hung out on thirdgen begging for knowledge that isn't really written down anywhere in a comprehensive way. I had some bad luck though, because I bought a kit that came with the wrong injectors and a bad computer...

My truck runs great now on TBI and starts immediately, but I'm still paranoid that I have this mystery box with custom stuff in it that nobody in the world will ever know how to fix but me. Part of my problem was that I had no emissions junk and wasn't interested in adding them when I did the TBI. This makes my chips and stuff unique. If you bring over then entire factory system including the computer controlled EGR and all that, you'd at least have a model year to compare against and be in common with.

 

[Kay86K5]

With so many fancy kits on the market most folks frown at tbi but surely it's better than a carb, right? Some local folks have suggested that tbi is too restrictive and say I'd better just as well off with a nice SMI or Jet q-jet. Could this be right? Doesn't seem possible to me.

I think it really depends on who you talk to and what you want out of your motor. I know a lot of guys on pirate bash TBI's because they are not easily tunable for built, high horsepower motors. With the specs of your big block, it looks like it could push some pretty decent power. The nice thing about the EZ EFI's and Atomic EFI's and all those systems is that they are built to handle really high power if that is what you want/have, but like you said, they are freakin expensive. If all you really want out of the deal is the reliability of fuel injection, than TBI is probably the cheapest and easiest way to go. TBI's really are a simple setup and are relatively easy to maintain. With the specs of your whole rig, even with 43's, I think you have plenty of gearing to have your 454 still feel really strong. But if you are a motor guy and really want to wake up that motor, probably those fancy aftermarket kits are the way to go. Once again, I guess it depends on what you really want out of fuel injection.

I just purchased a wrecked 89 k5 and am pulling the entire TBI350 out and replacing my carbed 383 with it right now. I got a bunch of crap from people saying that it was stupid to ditch the 383 and loose displacement, but overall, I could care less about horsepower. I rock crawl and that's it (I hate mudding and have never taken my rig in the sand and never plan to, so high horsepower stuff doesn't appeal to me). So I care more about not puking on off-cambers while rock crawling. So with that being the case, TBI is the cheapest and easiest way to go for me.

Don't know if any of this helped, but I have heard a lot of guys complain about TBI and I think more people need to stop and think about what they really want out of their truck/motor and they will be happier with their overall decision

P.S. before I ever purchased my new K5, I constantly looked at pics of yours with envy . Seeing pics of yours is what made up my mind to get an abomb bumper center! Your rig is sick.

 

[nvrenuf]

I understand what you're saying about customs parts & chips as I'd be in the same boat. As for the carb, if I don't go tbi I'll have buy that which will be $450-ish. That is the tricky part because the cost of the carb is probably a little over half the way to tbi.

 

[nvrenuf]

Yeah, for as much as I'd love to have a raging, fire breathing motor it simply isn't. It really is a lot milder than I thought it would be even though it should put out around 425hp and 500tq. I'm really just looking for a smooth running fuel system that gives painless cold starts.

P.S. before I ever purchased my new K5, I constantly looked at pics of yours with envy . Seeing pics of yours is what made up my mind to get an abomb bumper center! Your rig is sick.

Thanks! You obviously have a lot of patience if you've been watching my build, Lord knows I've drug my feet for a loooong time.

 

[dyeager535]

If money is a concern, any reason a stock harness and sensors won't work?

GM used the same sensors on about every car and truck from 1985-1995, so if you can stand used, those should be dirt cheap from wrecking yards.

Wiring harness might be a bit harder to come up with, but again using a stock harness, I can't imagine a yard getting more than $100 for one, complete. You could build your own as well, but that's a bit more effort and time, if you care.

EFI of any type will never be beaten by a carb in one aspect (when working right) and that's driveability. As anyone else who has owned both know, there is much to be said for something that starts and drives no matter how hot or cold it is, and idles nice.

As was already mentioned, really comes down to what YOU want out of the thing.

 

[Avery4jc]

TBI rocks! The guys that tend to have problems are the ones that pieced together a bunch of old junkyard crap instead of buying new. I bought my kit from affordable fuel injection and it was 100% complete and never needed anything after it was installed.

I've had it at sea level while in the dunes and all the way to 10,000 feet at dusy ershim trail and it has never missed a beat.

I've personally installed a howell injection kit and had issues. A guy I wheel with has the msd injection and has issues and a third guy I wheel with HAD a pro-flow kit and had nothing but issues so he yanked it and bought a kit from affordable fuel injection after seeing how much I liked mine.

 

[Mastiff]

TBI rocks! The guys that tend to have problems are the ones that pieced together a bunch of old junkyard crap instead of buying new. I bought my kit from affordable fuel injection and it was 100% complete and never needed anything after it was installed.

Did you install all the emissions stuff too, so it's exactly the same as factory, or did they give you a semi-custom setup? Bigger injectors or bored out TB would also make it custom. The thing that bugs me a little is if I'm far from home and something on the computer end goes south, what can I do? A factory computer may not run the engine.

 

[dyeager535]

You'd be in the same boat if your ignition module or pickup coil died, right? The PROM (the actual programming) is removable from the ECM, so replacing the ECM isn't a real issue. The fact that they rarely fail is another aspect to look at. As a matter of fact, I'd wager that just about every factory ECM out there, has outlived at least one distributor component that stopped the vehicle in it's tracks.

Emissions stuff isn't needed. Some of it I think is smart (EVAP), but AIR and EGR just aren't if you don't need to pass a visual inspection. Program that out of the chip (again, PROM) and you are done with. Even if AIR and EGR are removed, but the chip not changed, the engine will still run fine. Neither has any bearing on how the engine runs if removed, as the ECM tests EGR for function (so if it fails, the ECM knows not to modify fueling like it was still there, unlike carbs in the same situation), and AIR is post-combustion so wouldn't matter anyway.

 

[Mastiff]

I think the engine might run poorly with an EGR mismatch between chip and reality. When it turns it on it expects the lean/rich situation to change. It may just be a minor irritation, I'm not sure. In my case I programmed all that stuff out (EGR plus a few other things I forget now).

In my case I have an EBL-Flash from Dynamic EFI. It's based on GM TBI with mods to allow better monitoring and reprogramming, and some code improvements.

Anyway, I agree this stuff is reliable. My thinking was whether (a) you have a prayer of fixing your vehicle with stuff available at the local Autozone, or (b) if you needed could you punt and ask a mechanic someplace to fix your stuff. With totally non-standard harnesses and chips (and I don't even have chips anymore, flash ROM instead), the answer to the second question is no. If you have a very custom setup, who knows if a factory tuned computer will run the engine.

If I start taking my rig on long trips again, I'm going to really want a spare computer. Maybe one of my spare 7747s will run the engine with the right chip, or else I'll need to buy an EBL-modded one and pre-program it to match my current tune.

 

[Avery4jc]

Did you install all the emissions stuff too, so it's exactly the same as factory, or did they give you a semi-custom setup? Bigger injectors or bored out TB would also make it custom. The thing that bugs me a little is if I'm far from home and something on the computer end goes south, what can I do? A factory computer may not run the engine.

I just have a water temp, O2 and MAP sensor besides the sensors built into the throttle body (which is a stocker, just rebuilt) and the distributor is controlled by the computer like a factory TBI setup. It's all incredibly simple once you get your hands on it and yes, regardless of "custom" harness I could get almost every piece of my system at the local Auto Zone.

If you play the what if game you'll never go anywhere. As with anything prepare as best you can but in the end you can't carry a spare truck.

 

[nvrenuf]

I actually had an OE harness but sold it because I'm looking at the Howell harness without the distributor hook up (I really want to keep my MSD stuff). I like the idea of a simplistic system with just a handful of sensors.

As for budget, money is but isn't an issue. As it sits I'm at least looking at buying a better carb, my current Holley just isn't running good and while it was good for bogging I know it probably won't perform well crawling. I'm considering an SMI q-jet for $395 + freight + $50 plumbing. I already have a (theoretically) good 454 throttle body from a running Sub so I figure if I can put together the rest of the system for a little more than the cost of the SMI carb then that seems like the obvious way to go. Also, since my K5 is a '91 I'm already using the OE in tank pump and plumbing. All that said, a $1500+ system just isn't in the budget hence the carb or cheap tbi set up.

My biggest "concern" has been will the motor run good with the tbi, it sounds like it will. I just want to be careful I don't go with a restrictive set up. I know it won't flow like an expensive high hp aftermarket system but I'm also not rock bouncing or drag racing. I just want it to provide good reliable performance mostly likely in the 2500-4000 rpm range. The most should peak around 5500 so I won't need the ability to flow big at high rpm either.

I feel like I'm rambling... Am I making sense?

 

[bp71k5]

If you are planning on crawling, don't bother with the carb. They are fine for the street, but it sucks having the thing die on you halfway up something steep. The TBI is insanely reliable and can make plenty power if you get stock big block parts. I used a stock harness from a k5 from 4x4high that I tweaked. All the components are stock except for the chip which I can move to another computer if needed. Even the stock chip ran good enough if needed. All for under a couple hundred bucks, not including the chip.

 

[nvrenuf]

Are there any upgrades for the throttle body itself that I should consider? Bigger injectors? Adjustable regulator? Etc...

 

[Mastiff]

Are there any upgrades for the throttle body itself that I should consider? Bigger injectors? Adjustable regulator? Etc...

Not sure on 454 stuff, but there are all kinds of opened up 350 throttle body options. Just my opinion, but I'd really stay away from the non-factory stuff for all the reasons discussed above. I started out with a bored out throttle body on my setup and it raised all sorts of questions about what the problem was when it didn't work right away. I think people who think TBI swaps are easy are people who just grabbed a factory setup and dropped it in. You might get lucky with a modded setup, or you might go down the rabbit hole of burning a million chips while half-guessing the purposes of the hundreds of tunable parameters in these things.

Isn't a stock 454 enough for you?

 

[POORBOYK5]

I actually had an OE harness but sold it because I'm looking at the Howell harness without the distributor hook up (I really want to keep my MSD stuff). I like the idea of a simplistic system with just a handful of sensors.

As for budget, money is but isn't an issue. As it sits I'm at least looking at buying a better carb, my current Holley just isn't running good and while it was good for bogging I know it probably won't perform well crawling. I'm considering an SMI q-jet for $395 + freight + $50 plumbing. I already have a (theoretically) good 454 throttle body from a running Sub so I figure if I can put together the rest of the system for a little more than the cost of the SMI carb then that seems like the obvious way to go. Also, since my K5 is a '91 I'm already using the OE in tank pump and plumbing. All that said, a $1500+ system just isn't in the budget hence the carb or cheap tbi set up.

My biggest "concern" has been will the motor run good with the tbi, it sounds like it will. I just want to be careful I don't go with a restrictive set up. I know it won't flow like an expensive high hp aftermarket system but I'm also not rock bouncing or drag racing. I just want it to provide good reliable performance mostly likely in the 2500-4000 rpm range. The most should peak around 5500 so I won't need the ability to flow big at high rpm either.

I feel like I'm rambling... Am I making sense?

Personally, I like the stock harness idea and stock dist. You can still use lots of msd stuff on the stock sys except for the dist (they make an aftermarket one, its just a stock billet replacement) I like it because of the parts availability. Module goes bad, walk into any parts store and get it. MSD box craps out, you can unhook it and still run stock ign. I'll be running MSD off road box, MSD coil etc with stock dist.

Stock 454 TBI is 670cfm If I remember correctly. Almost seems small but seems to work well on most applications. just my .02

 

[nvrenuf]

Personally, I like the stock harness idea and stock dist. You can still use lots of msd stuff on the stock sys except for the dist (they make an aftermarket one, its just a stock billet replacement) I like it because of the parts availability. Module goes bad, walk into any parts store and get it. MSD box craps out, you can unhook it and still run stock ign. I'll be running MSD off road box, MSD coil etc with stock dist.

Stock 454 TBI is 670cfm If I remember correctly. Almost seems small but seems to work well on most applications. just my .02

I'm not really scared of the MSD parts dependability, I've been running this 6AL box and distributor for literally 15 yrs with no failures (hopefully I didn't just jinx myself).

As for the throttle body cfm size, I questioned Howell about that and the guy said fuel injection doesn't need to be as big because it's working so much more efficiently. Might just be a sales pitch but I does make a little sense.

 

[nvrenuf]

Isn't a stock 454 enough for you?

recheck my user name please