1984 GMC (kinda) slow build, Part 1.

[Blessed66]

"There are two secrets to success. The first, don't share everything you know."

And then there's this build thread. I am by no means an exceptional mechanic, welding wizard, wiring guru, suspension bodhisattva, etc. And I am definately on the lower end of the income bracket. However, I am meticulous, inquisitive and experimental. This will be a fairly slow build thread, so do not expect daily updates, but I will be catalogging the changes I make to my 1984 GMC LWB.



Some history; this truck was purchased gently used by my maternal grandfather sometime in the early 90s from his neighbor, who was having health issues and passed away some time shortly after that. I rode with my grandfather many times in this truck and always liked it. Never really knew if I wanted a truck like it, or not, but after he passed away - the truck just sat. My mother and aunt couldn't really agree on what to do with it. That's when I decided someone needs to take care of it. If there's one thing I cannot stand, it's a decent truck rotting away (especially when it's in the driveway right next to my house). So, with blessings from my mother and aunt, I drove (barely) it over to my carport and devised an idea of what I wanted to do with it.

This truck, like my '66, is an heirloom truck. Both my late grandfathers were the former owners of these trucks, and I'd love to one day let my sons drive them (after they've gotten past the reckless teens and early twenties - I'm not naive). But, with a condition that I would freshen the trucks up to be appealing, but not gaudy, and be mechanically capable of being depended upon for another 31 (and 49) years - barring some earth shattering change in technology, like the discontinuation of all SBC parts.

Step 1 (by far the most exciting to me) will be to convert this truck from the antiquated carb to a TBI fuel injection. Cheap, dependable, functional.



After scoring the TBI unit, and currently awaiting the computer and harness, I've been getting the sheet metal off the front of this old truck, because while I may have had no problem crawling under the hood of these trucks 10 years ago, time has not been kind to my body. Sitting on the tire seems much more appealing. Truthfully, if you've been hesitant to try this, I urge you to do so. You can take the fenders off without removing the bumper, so long as you unbolt (or cut ) the inner fenders and get them out first.





I can honestly say that, for the time being (remember, I'd need a $100 loan to be poor) I'll leave the 305/TH350 in the truck. I'm sure it's been worked hard over the years, probably has some cylinder wash, and generally... as the common consesnus is (for good reason)... it's a 305. I'll run it until it grenades, or I get my hands on a decent 350. Or, I might just break down and tug the 350/200-4R from the '66, if I get real desperate.

But that's a build for another section.

I'm currently in the midst of inspecting sheet metal, squirting some rattle can primer over some of the worst spots (the hood, in particular), and waiting for parts. There's a reason for the quote at the top, also. I plan to tackle the EFI first, and give a complete, real world breakdown of difficulty, cost, etc. for those interested. I do work for a parts store chain, but to be fair I will post true prices for the parts I have to buy, correct at the time of the post, and the part numbers used.

Along with that, I also highly suggest checking this post by user cjracing15 detailing the basics of the TBI harness and where the wires go, along with this 3-part install from DIYautotime.com converting to EFI. I will add more links in later posts, if it would please anyone, and will be as thorough as humanly possible with my details (I tend to make a lot of notes).

[Blessed66]

Texas has finally started to get cold. It only took until the end of December/beginning of January, but it finally feels like winter. We were having nice 60-70 degree days and 40s at night. Lately, it's been almost impossible for the temperature to get over 50 degrees, and it's usually when I'm at work and can't do anything. Figures. At least I'm in no rush.

I did get a wild hair and decide to lay some primer on the truck's hood. I don't like rattle can primer, but Duplicolor has a Primer/Filler that was, actually, not bad. Decent coverage, real smooth stuff. If you're in a pinch, I have no complaints. Been debating getting the truck painted, anyways, after everything was buttoned down and any bugs worked out of the TBI retrofit.

Speaking of, the wiring harness and computer arrived yesterday from a member here who happened to have one laying around (thanks, again). I've been doing some reading (in the link from the first post) on the wiring harness. I've got a nice little bit of paper devoted to what I'll have to do, in terms of retaining some of the wiring harness that's on the truck and splicing this 87 harness in.

A few things have come up that I'd love to get some feedback on.

1. I'm going to need a distributor for the TBI HEI ignition, which will not be an issue, but I'm debating my fuel delivery options. From the best of my understanding, my 1984 has a mechanical pump, a transfer pump, and no other pumps. Nothing in the tanks except sending units and pick-up tubes. I could likely find a decent enough pump to run inline, but I can pick up a sending unit/pump/hangar assembly for an 87 (brand new) for a little over $100.

There shouldn't be any issue swapping the 84 for the 87, I would think, but if anyone knows for sure, it wouldn't hurt my feelings if you let me know one way or another.

2. Jags That Run (JTR) sells a nice VSS that I will be getting my hands on, but I seem to remember there are many instances where people do not use the VSS and seem to run into no issue. Does this have more to do with the transmission (TH700-R4/4L60/4L60e) than the actual TBI engine?

3. Considering this is being done in a carport/driveway, I don't plan on doing a whole lot to the engine in the truck. Until it blows up. While the front clip was off, I did want to go ahead and remove some of the excess stuff on the firewall while I'm in the middle of doing the retrofit. I guess what I'm looking for is what items won't leave gaping holes if I take them off. If you have a decent before/after picture of the stock firewall vs shaved/cleaned up firewall prior to any hole filling, I'd be very appreciate to see if for reference purposes.

Thanks, guys. Looking forward to the sweet fuel injected cold start.

[LostMy65]

I'm going to be along for the ride.

[cdub2010]

I wish I could be in Texas, its snowing and 20 degrees now. I'm in the middle of the same job. A TBI swap into my '77 GMC 4x4 LB, "Lucky" for me, my '87 Jimmy's frame rusted out along with the rest of the body. I'm slowly moving all the good stuff to (drive train, interior and wiring) my '77.

I have the drive train, wiring and fuel system all installed and running. I have a stuck egr valve so it idles like crap. Hoped to fix it today but nothing in stock around me, gonna order from rock auto.

I'm working on wiring up a newer electronic speedo cluster from a '90 suburban I parted out. Id probably recommend getting a new TBI harness if i were to do it again. I spent a lot of time cleaning the harness as well as integrating it into my Frankenstein truck.

Some of the bigger expenses were gas tanks, I bought new 20 gallon tanks with pumps and sending units from Rock Auto. Ill have to cut down my rear driveshaft to fit the 700/241, I had an old one from another truck so its not too expensive. Good luck with the swap, A donor truck is an immense help with all the little parts. plus being able to see how it was put together is a plus. I would never have done this if I didnt have a low mileage TBI motor and trans ready to go. I would have went with an LS motor. Oh and yes its so much easier with the front fenders and core support removed.

[Blessed66]

I warned you, this was a slow build. Unfortunately, a work situation made it a little slower, for now.

Small updates (no pictures, yet);

I picked up a brand new TBI HEI distributor unit for less than a bill and got that stabbed with minimal issue. I know I will need to set timing more than just by "feels good!" as a parameter, but the biggest challenge was just getting motivated (the aforementioned work situation) to get back on the horse and keep working on my truck. Stabbing a new, improved dizzy was a nice confidence booster.

I have also purchased a slick Trans Dapt adapter plate to mount the TBI on the QJet manifold. It's a solid, thick metal plate, mounts it over the secondary venturi location on the manifold. Full throttle plate opening and no binds. I cannot complain.

Also took this as a grand opportunity to pull the clunky stock manifolds and man, oh man... exhaust flange studs. Those suckers fought me until they broke, and I promise, that was not on the first try. The alleged exhaust in the truck now will be replaced (eventually) with headers (because, free) coming to a Y-pipe (because I require an O2 sensor), and something quiet with a decent rumble. It's not gonna turn a bunch of heads, but I want a decent sound, regardless.

I also removed the dash pad, and fed the OE 1987 TBI wire loom through the provided firewall hole (direct fit, gutted the original 6-7 wires that passed through originally).

For anyone taking an OE harness and retrofitting it, I cannot stress enough how simple cutting the extra wiring (that would normally go to the firewall junction beneath the wiper motor) off the donor harness. You end up removing the ALDL and MIL hook-up, but that can be relocated and completely reworked. I swear, it took about 1/3 of the wiring harness out of the cluster of wires I'm working with.

Next items, for those interested;

I want to drop the left fuel tank to ensure what size line is there, but I'm betting 3/8" and 5/16" with a smaller vapor line.

Order in Metric O-Ring to AN or hose barb adapters (for the TB supply and return lines), and run new hoses and a universal inline pump that meets the GPH and PSI requirements (spoiler, it's only $60).

Those two items are the bare minimum, I believe, to get the fuel system ready. I've seen the mention of a baffled EFI tank, but I don't believe it to be 100% required for this application. Running the stock pick-up/sending unit and gravity-feeding a 15psi (max) inline pump - I doubt it would be a major issue, even at 1/4 tank.

Still have some loose ends to tie up in sensors and EFI stuff (Coil, ESC Module, Knock Sensor, CTS, MAP, rewire for later-style TPS, figure out what I want to do about the EGR stuff, etc), but I just wanted to let you guys know it's coming along and I'm still here...

...now I just need a good job, for a change. But that's a subject for off-topic.

[lowandlong]

I too have and 84. It's a GMC sierra classic. im starting with the brakes and suspension. do you know what your plans are when it comes to that?

[lowandlong]

I new to the forum, what are your suggestions on were to start?

[Blessed66]

Originally Posted by lowandlong

I too have and 84. It's a GMC sierra classic. im starting with the brakes and suspension. do you know what your plans are when it comes to that?

I new to the forum, what are your suggestions on were to start?

First, Welcome to the Forum.

Second, I plan to leave the brakes and suspension mainly stock, at this point. The future may hold bags or a static drop, but at this point I just don't want to bite off more than I can finish in a timely manner. The fuel injection conversion in almost wrapped up, really.

I may want big brakes, bags, or that slammed look... but I suggest to anyone to take it a step at a time, unless youre confident in you wallet or your ability.

[lowandlong]

cool, thanks.

the truck I just bought is running and not in bad shape....eventually I would like to improve it. so im starting with a static drop and wheels. I will try to post pics. not sure how to do all this.

[Blessed66]

Looks pretty good, to me. Congratulations on your new ride.

[Blessed66]

Well, got some goodies on the way...

TBI to Air Cleaner spacer (OE style) and stud (aftermarket), supply and return hard line sections, new coil to distributor wiring harness, newer style TPS pigtail (have the older harness)... that should be a majority of my "Oh Crap, I don't have (blank)" purchases.

Going to convince the Mrs. (I hope) to go ahead and splurge on the remaining parts because, at this rate, I'll only have a few more hours of work tied up in this thing. I decided to go ahead and piece back on the sheet metal. Naturally, things aren't lined up (say it ain't so!) 100%, but the hood and fenders are back on! No inner fenders, but I have a solution I will get to. Eventually.

Again, not going to be driven daily, so I can leave a few things "poor and in a hurry" for now...

And...



Blurry shot, night shooting with an old digitial camera because my spiffy one on my phone is gone (dropped a few times, the struggle is real). Don't mind the multi-colored hood. I got bored waiting on parts so I decided to watch paint dry instead.



Left Front Fender/Cowl/Door. Kinda sketchy.



Right Front Fender/Cowl/Door. Makes the other side look AMAZING by comparison. Luckily, everything is bolted together with just a handful of bolts, so adjusting the alignment won't be too bad. Wouldn't mind expert advice, though.







Some of what I've been up to around the engine. That mess of wires? Really not as bad as it looks. I have (almost) all of them a home and will be looming and taping everything up when I get it plugged in. I guess my line of thought is I want to have it all unwrapped to check for bad wires (the 4-pin distributor plug will need to be fixed) and then wrap it all up in a routing that won't be a pain to take off at whatever point I yank the engine.

Just enough to get it running, but no where near as amazing as some of the people's builds I've been inspired by, here.

Just for clarification, I know what I'm doing isn't 100%... optimal, I guess. Truthfully, this is one of the first times I've taken all that "book knowledge" years in this business has given me and actually applied it. So, it looks bad, now... but eventually, I'll polish this turd up.

[LT7A]

Good luck man. I have a 93 TBI truck that I love and am working on a carbureted 82 project now. I'll be interested to know how the swap goes, and how the starting and driveability improves.

[Blessed66]

Originally Posted by LT7A

Good luck man. I have a 93 TBI truck that I love and am working on a carbureted 82 project now. I'll be interested to know how the swap goes, and how the starting and driveability improves.

Thanks, I'm excited to see for myself. I don't anticipate it to be a major difference - maybe that's just keeping my expectations low - but cold starting/operation and maybe a hair of fuel economy increase? Don't know, will find out soon.

[Blessed66]

Picked up some packages from the post office today!

Received:
OEM TBI Air Cleaner Spacer
Air Cleaner Stud
Dist to Coil harness
MAP Sensor
O2 Sensor

Still waiting:
Coil
ESC Module
TPS pigtail
CTS (not -V, sadly)
Dorman fuel hard lines (short)

I also got a chance to hit my Friendly Local Parts Store™ (who, in truth, is not very friendly, or local) and pick up some wires, a fuel pump, and some assorted odds and ends (wire, connectors, electrical tape, etc) but they were out of 3/8" fuel hose? I was astonished. Oh well, I'm not ready to mock up the fuel delivery yet, so I can live with that.

Just wanted a quick parts update, because I feel this "kinda" slow build has actually made some decent progress - in spite of the universe throwing me curve balls. For a one guy (with questionable mechanical ability) job, at least.