1991 K5 LO5 Engine replacement

[Rhinodrvr]

I am in process of replacing the LO5 in my 91 K5.

I am getting the GM replacement motor (http://paceperformance.com/i-648501...mc-full-size-trucks-g-van-up-to-7200-gvw.html).

My question is regarding the TBI. I am debating replacing the stock intake and TBI with an upgrade. Are there any recommendations any forum members are using with reliability and solid performance? Would I be better off doing a short block and then adding the Vortec heads with another TBI version?

Ideas or advice are greatly appreciated.

Thanks.
Rhinodrvr and MegaPig (K5)

 

[jekquistk5]

Well that depends on if you are using the stock ECM or not. If you plan on using the stock ECM you will need tuning to gain any performance.

There are a ton of off the shelf style tbi style self tuning units. Fast seems to be the best one, and is good for any size motor. All depends how much you want to spend really.

 

[eagle mark]

That's not much more then a stock motor and will run fine with stock TBI injection.

 

[cuervo]

I put that exact motor in my 87 Jimmy with any tuning. It worked very well.

 

[dyeager535]

Just to chime in, were you thinking the stock TBI itself was a limiting factor?

Without going to something like port injection (and even then to a degree) TBI isn't really a limiting factor, nor is the intake. If anything the heads and cam are, but those are designed to make low end torque, which is perfect for trucks.

Yes, more power can be had with a larger TBI, larger injectors, better fuel pump, better intake, better heads, better cam and better exhaust, but that's a big leap.

 

[Rhinodrvr]

Just to chime in, were you thinking the stock TBI itself was a limiting factor?

Without going to something like port injection (and even then to a degree) TBI isn't really a limiting factor, nor is the intake. If anything the heads and cam are, but those are designed to make low end torque, which is perfect for trucks.

Yes, more power can be had with a larger TBI, larger injectors, better fuel pump, better intake, better heads, better cam and better exhaust, but that's a big leap.

The TBI is just what I have immediately available. Plus I don't want to affect the warranty. I am not opposed to other injection set ups...my brother and I discussed using the 454SS pickup's TBI with a 9C1 style manifold. We even discussed doing a short block and building with VORTEC heads. I don't want to get overboard but want to be able to enjoy the truck with out having to worry about tuning, changing computers or modifying the computer.

I still have to do exhaust... I have straight pipes with magnaflow mufflers and 4" outlets. I think i need to do an H or X pipe with Flowmasters and going to a flat camaro style outlet tucked up near the rear bumper. Any thoughts?

The new wheels and tires.

and then...fresh paint.

 

[dyeager535]

Realistically anything you do to modify the engine (including intake and exhaust) requires tuning. The only way around that is to stick with a bone-stock engine. Yes, it will run "fine" up to a point without programming, but that is an inherently bad idea, as you are relying on the safety margin GM programmed into the system, and once outside that margin, well, bad things can happen.

As to exhaust, my belief anymore is that unless you simply cannot do so, or HAVE to have duals for looks, single is better in every regard. Cheaper, easier, more reliable, more than enough flow with 3" pipe, and less cluttered under the truck. I've got duals now, I will be going to single.

 

[eagle mark]

I don't want to get overboard but want to be able to enjoy the truck with out having to worry about tuning, changing computers or modifying the computer.

Even stock the chip has loads of room for improvements!

Once mods are done then the vehicle can even run worse then before mods without changing the chips programming.

If your willing to do all this work then why not add what is truely important and get a good tune? It's cheaper then any of the mods your considering. All you need is a cable and laptop to datalog for a good tuner. Chip comes and you slip it in and POOF! Best mod you've done!

I did a starter tutorial for guys who want to learn tuning. If you don't want to learn then half of it is not neccesery, just the data logging part which is also your scan tool you must have if you own a EFI vehicle.
http://coloradok5.com/forums/showthread.php?t=302680