<img src="/forums/images/graemlins/smile.gif" alt="" /> I posted a while back on opinions between the 4.3 GM TBI and the Holley unit. I decided to go with the 4.3 when I found one in the For Sale section here for $40 <img src="/forums/images/graemlins/kewl.gif" alt="" /> (thanks George!)

I also found a 2.8 intake manifold on eBay for $50, which came with a 2.8 TBI that I will put back on eBay to offset part of my project costs! <double grin>

I've printed out all the conversion articles here, so am ready to get started! Has anybody seen this article or tried any of these mods? Chevy/GM TBI mods

I think I'm going to give them a try since I'm going to throw a rebuild kit in it anyway before I put it on.

It's probably going to take me a while, but hopefully it'll all be on before summer!

Jay

I've always liked the 4.3L...it certainly gave excellent power and better than average fuel economy in my 97 Blazer.

Looking forward to ongoing swap updates! <img src="/forums/images/graemlins/kewl.gif" alt="" />

He's talking about just swapping the 4.3 TB and intake manifold. People sometimes use TBI and "throttle body" interchangeably, it is confusing but seems like everybody says it like that.

Ahhhh...OK...so what is actually gained with this swap? Fuel injection? Just curious...

You increase the throttle bore from something like 1 5/8" to 1 11/16".



The mods described in the link would theoretically decrease incoming air resistance and turbulence by tapering the throttle bores and shaving the throttle shafts.

Lifting the injector pod with a spacer theoretically should allow for better high-rpm fuel atomization, but, according to some tests, decrease low-rpm throttle response. This mod is similiar in design to a TBI spacer, by lengethening the intake manifold runners.

No, the 2.8 comes with TBI (throttle body injection) already. Looks like a 2 barrel carb (two injectors in a 'pod') as opposed to an MPFI (multi port fuel injection) setup like the 3.2/3.5 and I think 2.3/2.6 4 cyl engines with an injector for each cylinder. On those setups, the throttle body only flows air, rather than the air/fuel mix as a TBI does.

The swap to the 4.3 injector body (you still use the 2.8 injectors) is supposed to flow more volume through the engine and improve the HP and torque. The 'new' intake manifold is because the stock one has bores sized to match the stock TB (duh...), so to increase the flow, the bores need to be enlarged to match the bores of the larger TB.

By buying another manifold, it just reduces my downtime for the swap. I can have it bored out while still driving the Trooper, then, when I'm ready, take off the old one and swap the modified intake manifold/4.3 TB onto the engine, hopefully over a weekend and be able to drive to work on Monday.

Basically, like swapping the stock manifold and carb on a 60's small block V8 for an Edelbrock manifold and Holley 4 bbl!

Chris made a nice write up of his version of this swap, I'll go find it and post the link...

[edit]http://www.4x4wire.com/forums/showflat.php?Cat=&Number=415804&page=0&view=collapsed&sb=5&o=14&fpart=1#Post415876

And Chris showed up with a pic in the meantime![/edit]

I'll get some pictures of the parts and add them, that should help too.

Jay

Not to nit-pick, but this mod will not flow more air (in terms of volume) through your engine.

It just decreases the amount of power needed by the engine to suck in air on the intake stroke by limiting resistance. The only way you will get more air in your engine is by increasing displacement, or adding forced induction. This is the reason you stay with the same size injectors.

Not to rag on it though, it is a great cheap mod that will increase throttle response and top-end HP!! (especially combined with exhaust mods)

Pick away! If I knew everything, I wouldn't be here asking questions... <img src="/forums/images/graemlins/lol.gif" alt="" />

I'm sure I'll have lots more before this mod is over too!

BTW, good stuff about the spacer underneath the injector pod, I hadn't thought that all the way through yet. Makes sense and top end HP vs. low end throttle response is not (IMO anyway) where you want to go with a 4x4...

Jay

Here is one way to make the fuel lines work with a 1" spacer on a TBI. All I did was fliped the fuel line 180 deg.

see pic:
<img src="/forums/images/graemlins/kewl.gif" alt="" />

Geez...

I'd almost forgotten I made this post... <img src="/forums/images/graemlins/frown.gif" alt="" />

How things can change. I still have all the parts, but my Trooper died for good (well, died and wouldn't restart easily at a point when I didn't have time to mess with it), so it got parked off the side of my driveway and has been sitting ever since.

Work and home life have been too hectic to take the time to fiddle with it and I haven't been willing to part with the $$$ to take it to a mechanic.

Knock on wood, things are starting to calm down a bit and if monsoon season ever lets up (record rainfall for a couple of months in an area known for it's rainfall), I hope to do some diagnostics and get it on the road again, then pick up on these mods...

Jay