Congratulations Jim! <img src="/forums/images/graemlins/cheers.gif" alt="" /> Now, where are the pics of the new engine/install?! Would like to see it.



Now, I've not done the 4.3 TBI swap yet, but, with all of the reading that I have done (and may remember correctly or incorrectly) did they not use the 2.8 injectors in the 4.3 TBI? Or, was that, don't use the 4.3 injectors in the 2.8L, but use the 4.3 injectors in the 3.4L? Can someone clarify this? <img src="/forums/images/graemlins/notooth.gif" alt="" />

Jim

Jim, you can run a 4.3 TBI with either 3.4 or 2.8. A stock 2.8 might be a bit rich with 4.3 injectors so usually you'd put the 2.8 injectors in the 4.3 TBI.

For a 3.4 application, you need more fuel so you'd use the 4.3 TBI as is.

If you were to stick with a stock 2.8 TBI on a 3.4, you'd get lean surging on warmup. Installing 4.3 injectors in the 2.8 TBI's injector pod will cure the lean surge but you're limiting the midrange and top end of the 3.4 'cause it wants/needs more air/fuel.

I used a Holley Big-Bore TBI (roughly the equivalent of a stock GM 4.3 TBI) on my old 2.8. That motor was hot-rodded with larger exhaust, bored intake, jacked-up timing, flipped lid/K&N, and 1.6:1 roller-tipped rocker arms. It ran quite well with the Holley but was just a wee bit "over carbureted".

Putting a larger TBI on an otherwise stock 2.8 would be overkill, since unmodified this engine just can't flow enough air to achieve significant HP gains.

Once uncorked at both ends, using Good Old-Fashioned hot-rodding techniques, it'll really wake up.

Anyway, hope this clears it up a bit.........ed

P.S. Other Jim, Good Job! on the swap. Now get'er run-in, tweaked-out, and enjoy the ride! Your ECU will take a while to adjust to the new motor, and you can pull trouble codes out of your auto tranny's computer to see what's going on there.

Ed,

Thanks! You've been a big help with this here project. What I did was this... put the 2.8 TBI on the 3.4, but with the 4.3 injectors to compensate for the greater airflow of the 3.4, which would run too lean with the 2.8 injectors... whew! I read it on this site, anyways... I have a stack of printouts on this swap! Besides, I didn't have time (or the right parts at the time) to rebuild the 4.3 TBI, or bore out the intake.

As far as pulling codes, I haven't the faintest. I can't seem to find pictures of wiring, diagrams of where to look, instructions that make sense... all I know is the CTL doesn't come on for approx 20-30 seconds after starting, starts blinking really fast (2-3 times a second) and by whacking the throttle, it goes off until the revs drop.

Duh. And I looked under the dash for the trans box (from the other post) and I haven't a clue. There's nothing under there that says "transmission" anywhere that I can see. Mr. Analog is lost here.

I think I'll go crawl underneath and look for unplugged wires that I may have missed, again. If I can't find an answer tonight, I may have to drive this thing to Cali with a piece of electrical tape over the CTL...

Other Jim

Thanks Ed! <img src="/forums/images/graemlins/cheers.gif" alt="" /> Your answer to my question is concise AND thorough. I really appreciate your post.

Jim

I'm a dope, officially. Two sets of wires, running along the left side of the intake, ending with large washers, calling out to be grounded - weren't. Bolt on the back of the left head, w/braided ground strap attached, when the two wires from the intake manifold loom were bolted down to the back of the left head - SHAZAM!

No more blinking Check Trans Light.

I saw that at like 1:30 this AM, but wasn't ready to go there.

Now you know, check all your grounds!

I'd bet that a 5/8" offset distributor wrench would work on that 15mm bolt... if not, maybe a crow-foot socket on an extension?

Randii

A 9/16 distributor wrench, a grinder, a file and I'd have been in business...except my files were too wide, my grinder was elsewhere, and my machinist pal down the street had gone home. Oh, and Sears was out of 15MM crow's feet attachments. Trust me, I looked. But a Craftman 15 MM Universal socket/12"extension, (not a socket/universal joint/extension) worked just dandy.

Update: Just returned from the trip from Seattle to Bakersfield, CA and back. 2270 miles. Haven't figured out the milage yet, but for having one day from firing up the conversion to hittoing the road and driving 1100 miles, everything went pretty doggone well. A couple exhaust leaks (retightening bolts and nuts worked wonders), do NOT overfill the auto trans and drive 85 MPH... it'll puke the fluid out all over the exhaust! Smoke everywhere. Looks pretty bad threading the 99 between semi trucks...still have an issue with the TPS (trans position sensor), as 4th gear (OD) can only be achieved by moving the shifter between D and Neutral, and holding your mouth just right.It's just too tight in between the exhaust & torsion bars to get into and adjust without jackstands or a lift... I did drive up on a curb Friday AM and managed to get it a bit better. But there was a ton of rain, too, and that kept me out from under.

Used some oil, but I may have underfilled at the start, so it may be a non issue.

Anybody got some 4:10's for a 91 Trooper they want to get rid of? I need higher gears... maybe a set of chevy truck wheels with 265 or 275/75/16's or 17's.

Jim Sorenson

After roaming though the various pages, I noticed that there were some questions about the "check trans light" flashing on the 4L30E trans. The trans goes into "limp" mode, no power...
Many times you will find that the fluid is scorched or oxidized. Half a can of Berryman's Chemtool B-12 and drive it for a few miles usually stops the problem caused by sticky valves or solenoids. Change the fluid and you are good to go.

People often take the auto transmission for granted and don't realize it also needs a little tender loving care -- as in a periodic change of fluids to keep things in good working order. Thanks for the information point and reminder...

Quite often the limp home mode is generated because of a broken wire in the harness.