1991 Diesel (conversion) Suburban

jjosu

Observer
I guess I should do a build thread. I wound up here due to Spur's epic '91 Cummins Burb build showing up on Google. That was my original plan, but economic realities got in the way. Can't say my real goal is a true "Expo" vehicle, but I would have to say this site has me thinking. Anyway, she's a '91 Burb 2500. Came with a 350 TBI and 4L80e. As you can see, the 350's been pulled (which revealed a reman 4L80e, which is a plus given the 180k on the clock). A 6.5 TD out of a '92 K2500 pickup is waiting in the shop and has been for about 6 weeks. Truth be told, I'm not entirely sure it's gonna run. It turned over with a half-discharged single battery, shows no obvious signs of catastrophic failure and was supposedly rebuilt 30k ago...and I paid $400 for it. Here is how the Beast - which is what my wife and 10 year-old son named it - sits today.

1217963.jpg

The shop is owned by a friend/former employee. Way back in 2005, I was the service manager at a Dodge dealership and Trent was one of my techs. His place is called Outlaw Diesel in Stillwater, OK. Truth be told, like most service manager/advisors, I always understood the basic principals of service and repair, but had virtually no experience turning wrenches myself. My only actual experience working on cars was as a installer/salesman at a car stereo shop in the early 90's, and maybe changing oil a few times. Anyway, I'm paying Trent for his time and he's letting me use his shop to do as much as I can by myself. Truth be told, I wasn't quite sure what to do when he handed me a pair of pliers to drain the radiator, but dove in and got most of the top side taken out, unhooked and unplugged. He finished up underneath disconnecting the tranny and motor mounts. Since then, I've dropped the tank and taken out the steering gear box (mostly) solo.

Along the way, I bought a '82 K5 Blazer with a 6.2, 6" lift and 35" BFG KM2's. The original thought was to swap over those three things.

1199375.JPG


It was advertised as having new KM2's. Asking price was $2500 for the K5 and an extra rebuildable 6.2. Checked it out at night and the engine had some serious starting, blow-by and leaking issues. The KM2's though? New was an understatement. As in nipples were still there on the main treads. I figured it would be hard to go wrong around $1700. Seller balked until I told him I had no use for the extra boat anchor. So I drove home my new tires (err, rig, I mean). Only problem with the tires was that they were for 15" wheels and of course my 8-lug Burb has 16's. And 15's with the right backspacing are pretty rare. Wound up with some Pro Comps that should work. I hope, but we'll see.

Found a set of 32x12.50's to fit the K5 and made the switch. Soon enough, I traded off the K5 for a Winchester 1887 lever action 12 gauge made in 1892. It has apparently appraised for $1800. I figure I have $900-1,000 in it.

So that's pretty much it up to date. Well, except Trent's part-time employee told me this morning he has a buddy who wants to buy the 350 and that he might want to buy the Winchester.

Up next is a shackle flip in the rear and new springs in the front and - finally - installing the KM2's and Pro Comps. Decided to go with 4" and the rear flip instead of taking the rear blocks off the K5. We're trying to figure out exactly what has to be done with wiring harnesses and PCM/ECM and/or TCM's. The Burb has a PCM. The '92 apparently had a TCM only, as the engine is (largely) mechanical. New gearbox, subbing hydroboost for the vacuum brake booster and a new torque converter install have to happen before we get the control module stuff figured out, so there is some time.

Also have front buckets and second-row seating from a '97 Tahoe ready to go in. There is fab work to be done there, and honestly we've barely looked at it. Any suggestions are welcome. Only thing I know for sure is the front bucket frames sit way too high on the outsides and will have to be cut down.

That's it for now, and I'd like to thank expeditionportal.com for all the Burb inspiration!
 

jjosu

Observer
Here's a pic of the Beast as it was when purchased. The Warn 9.5ti was sold off ($500) to raise build funds awhile back.

1163811.jpg
 

FellowTraveler

Explorer
Your build

Nice project, a mechanically injected 6.5 turbo diesel. Since this setup does not suffer the stalling starting issues of the newer electronic injected diesel the only thing I see you would need is a good fuel filter setup before the lift pump.

The lift pump for the mechanical injection is different than the newer pumps in that it pumps about twice the psi which the mechanical pump likes, using a newer pump designed for electronic injection (lower pressure) should be avoided. I use these early lift pumps in my 1999 Suburban for the extra pressure to IP.

IMHO, keep it simple increase intake and exhaust flow, a fluid damper, timing gear drive, egt/boost gauge then if needed marine injectors.

Good luck w/build!
 

jjosu

Observer
A new filter set up is definitely in the plans. A harmonic balancer or Fluidamper will get put on, but we decided to get the engine installed and test run before spending that cash, just in case it's no good.

We're currently trying to figure out what has to be done in terms of Control Modules and wiring. From what I've been able to gather, the TBI/4L80e combo had a PCM. The 6.5 TD (mechanical) and 4l80e would have a TCM with a handful of sensors from the engine feeding info to the TCM. Does this sound right? I do not have a donor vehicle on han
 

chilliwak

Expedition Leader
Welcome to the site JJosu!:Wow1: Always good to have new GM guys here. Even though things look like they are never ending regarding your engine swap, just take it slow and easy, and when you hit a snag the guys here on the site, or your buddy in the shop will help you out. I can see you have learned the first unspoken rule here, POST LOTS OF PICS!:Wow1: So I think you will enjoy your stay here. Keep up the good work and keep us up to date....:ylsmoke:
 

jjosu

Observer
Not a lot accomplished today. Removed the brake booster, as it needs hydroboost instead with the new setup. Did some cleaning around the PS gearbox attachment. Pretty caked with fluid and dirt, etc.

The lift in the shop should be freed up tomorrow, so hopefully we can get the shackle-flip and new front springs, plus shocks all around done this weekend. I went cheap on shocks for the time being (Superlift), but they have to be better than the 20 year-old stockers.
 

jjosu

Observer
Not much shaking on the mechanical front. That should change soon. We were hoping to get it on the lift Friday, but a simple transmission fix on a 5-speed turned into "new transmission" so the lift was tied up. At the same time, it occurred to me that moving around a 3/4 ton Burb with no steering was going to be interesting. Even though it needed to move about 40 feet to the right, it was still gonna be a problem. New gearbox arrives tomorrow, and hopefully will get installed so we can move it over as soon as the lift is freed up and get the suspension work done. In the meantime, I've been working on dress-up stuff. Pics below.

Old dash, trashed like most of them
1220263.jpg

Replacement dash. A factory original, with one TINY crack in the center grille. Otherwise pretty much flawless.
1220261.jpg

Another view of the new-to-me dash
1220262.jpg

New dash with painted insert (the good one in the background is still an option. Exterior will be flat black with Oklahoma State U orange accents
1220260.jpg

Grille insert, flat black
1220259.jpg
 

REDROVER

Explorer
dont forget to add check valve on your fuel lines , gasoline powered trucks dont have it, but diesel will have to have it, since your fuel pump is gonna have max of 14 psi,

6.5 is awesome
 

jjosu

Observer
Still not a lot happening.

Steering gearbox installed, front shocks removed. Currently waiting for the lift to free up in order to finish suspension work. Also waiting for some parts to arrive - torque converter, thermostat, diesel fuel sending unit.

Still unsure exactly what needs to be done on the TCM/PCM/wiring front. Looks like I need to acquire a 6.5-specific TCM and either buy a complete wiring harness, or have a custom one made.

Some good news? My buddy handed me $70 cash yesterday...he sold the old catalytic converter. I just handed it directly to his wife and told her to credit my account, though. :smiley_drive:
 

jjosu

Observer
No major update today, but I do have pics! The suspension work will begin tomorrow morning, hopefully.

The new-to-me 6.5 TD
burb engine 1.jpg

burb engine 2.jpg

Pretty much all the parts visible here are for the Burb.
burb parts.jpg
 

jjosu

Observer
Quite a bit happening today. Got the lift springs installed on the driver's front. Moved over to the passenger side and the leaf bolts will not fit through the bushing/sleeves. The springs are Superlift (I know, I know, I went cheap for now) and so are the bushings. Why one side fit perfectly and the other not at all, I have no idea. Called Sam's Offroad in Tulsa to get a different set. They don't stock them, but the guy I talked to said the 88-91 Suburbans and Blazers often have to go with just the polybushing and no sleeve to fit right. Anyone else ever heard this? I took some pics, will post em up later.

Other problems - the steering arm has not been cooperative coming off. The lock washers are fused to it. Also, we had noted that the front wheels sat a little crooked. Tried to correct it, but that required disconnecting the front drive shaft. That probably explains the rumble we had noted at any speed over 55. Looks like I may need a new one.

There was some good news. We're pretty sure all four shocks up front were factory original, and the front springs definitely were. They'd sagged to the point of almost bending a little in the wrong direction. Ride quality should massively improve, even with less than primo new springs and shocks.
 
Last edited:

jjosu

Observer
More PICS!

The Beast is finally on the lift
1222683.jpg

Lift on driver's front basically done. Steering arm still not resolved.
1222682.jpg

Passenger side before completion. Still needs one new leaf spring bolt to really be done.
1222681.jpg
 

jjosu

Observer
Other notes: Front drive shaft is hosed. There's no play in it at all. Someone before me hit something really hard upfront. Front axle is now properly aligned, but the drive shaft won't reach now.

Forgot to mention the bushing sleeve solution. I had six rear bushing and sleeve combos. Two came with the shackle flip kit, plus I ordered a set...so we test-fitted a pair of rear sleeves in the front bushings. Theywere not a perfect fit - they are not quite wide enough and a pain in the *** to fit inside the front bushings. That said, we decided that an imperfect sleeve inside the polybushings was way better than no sleeve. It actually worked pretty well in the end, I think.
 
Last edited:

jjosu

Observer
One final thing for the night (I think?) A decision has been made on the TCM/wiring issue. Thanks to some advice from thedieselplace forums, I'm going with an aftermarket, standalone TCI/TCU. As one poster succinctly put it, "it's not THAT expensive versus other options and puts you that much closer to a Cummins 12V conversion down the road." Also has a lot of available customization.
 

Forum statistics

Threads
189,829
Messages
2,921,377
Members
232,931
Latest member
Northandfree
Top