Project “Polar Bear”: 1989 V2500 Suburban

[Larry]

Yea my square body's all flexed too, but when I put the heavy utility body on the 1/2 ton short bed and the 3/4 ton suspension and axles I always felt another crossmember would have been benificial. Keep in mind I was building suspensions and chassis for off road race cars back then and every stock chassis cracked and broke.
I love the way you guys are running your tiltin hiltons through the trails.
Spotters are nice to help avoid driving over stuff that induces undue strain on steering and suspension.
The scenery looks fantastic!
I'll bet that trip was a welcome relief for Lance compared to the mud of the Expo.
Mud is OK but it is such a pain to clean up after, I usually set a lawn sprinkler under my vehicle for a day after a mud trip.

I could see that on a race truck. If mine ever launched into the air like a desert racer it would be safe to say it would be a catastrophic landing just as most any stock old school rigs would suffer.

...Glad to see I'm not the only one nuts enough to take a ECLB Cummins up technical terrain haha!

Good stuff as always Larry. Good numbers on the Polar Bear!

Hehe, yeah…my friends and I am either crazy or have balls to take full-size rigs the places we do. If you need a chuckle go lookup Lockhart Basin videos on YouTube. The best video to laugh (and cry a little) is the well-produced video of 3 Jeeps (TJ Ruby, Silver XJ and an older SFA Grand Cherokee) totally getting the snot beat out of them going over Lockhart. Some how they got the idea speed and spinning the hell out of the tires are required for maneuvering technical trails. The funny thing is the big rigs hardly spun a tire on that trail other than maybe a ½ rotation of a tire and not a single rig suffered an ounce of body damage or any carnage for that matter. The Jeeps in the other video didn’t fare so well.

Heheheh That dyno vid has me grinning from ear to ear... Nice work!! IIRC, the tune and cam were the only mods, aside from headers... Any idea how this 8.1l might compare to a stock one?

Great... I'm now back on the lookout for a GMT800 regular cab 4x4 with an 8.1, and a 6-speed... Unfortunately, I think all the forest service trucks that were equipped that way have been sold off now, and I doubt many existed in private hands.

Not really sure how a stock 8.1L would compare on the dyno but I seriously doubt my bone stock 2001 Silverado 8.1L would lay down anywhere close to those numbers. I can tell you all three of my 8.1L’s run entirely different. The Silverado being a bone stock virgin truck feels pretty wheezy compared to the other two as the stock ECM tuning is loaded with Torque Management and Lean Enrichment for powertrain protection. The K10 has a bone stock engine but the ECM has been performance tuned with TM, LE & EGR removed, fuel/spark maps tweaked and a bump in fuel pressure. The K10 feels much stronger than the Silverado by a long shot even with passing the fumes through exhaust manifolds. Then the Suburban runs entirely different than the Sily and K10 with the cam, shorty headers and ECM tune. I was really happy with how the Suburban turned out until today when I started it cold for the first time since the dyno tune where it went back to its hunting idle and dyeing when I ease off the clutch to move it. So with that, it became quite apparent the tuner didn’t address the open loop operation. I left them a voice mail and an email today and haven’t heard back yet. Looks like I’ll have to take it back and leave it overnight for them to do some cold start/open loop adjustments. Once it gets warm and goes into closed loop it runs like a sports car......or more like a sports car engine hooked up to a dump truck transmission :elkgrin:

A forestry service truck with an 8.1L/6 speed manual? That would be cool to find. I've only seen the forestry service GMT800's in 6.0L/4L80E form.

 

[Colorado_Outback]

or more like a sports car engine hooked up to a dump truck transmission :elkgrin:

Haha, speedy shifting the NV4500 is not.

I would be interested to throw mine on the dyno when its done, not exactly apples to apples with tire size and gear ratio. Sill I would be interested to see how my stock Howell tuned 8.1L compared to the modded Burb.

 

[Larry]

Haha, speedy shifting the NV4500 is not.

I would be interested to throw mine on the dyno when its done, not exactly apples to apples with tire size and gear ratio. Sill I would be interested to see how my stock Howell tuned 8.1L compared to the modded Burb.

For sure. The work I did below may help with the shifting...we'll see! I agree, it would be interesting to compare apples to apples. Heck, it would have been fun to see what the little 5.7L would have done before to get a good before and after result.


So I got a little annoyance thing addressed on the Burb last night. Since the NV4500 swap the clutch “feeling” has been a moving target. I find myself adjusting the clutch every few weeks and was getting pretty tired of it. Normally there aren’t any adjustments with a hydraulic clutch but with the Advance Adapters NV4500 bell/slave bracket there is. Anyway, I treated it to a new slave, M/C and hose as well has gone to much larger hydraulic reservoir. What a difference this all made! I’ll be able to put more miles on it later this week but it already feels 100% better.

Tiny OEM reservoir. I never though these were big enough to work properly in high temps.

Tilton reservoir mounted to a bracket I made that bolts to the bracket master cylinder and hydroboost hose bracket. I actually used a TBI 7.4L MAP bracket for this. Hey, it fit almost perfect! Now I want to do the same to the K10.

 

[Larry]

Finally got around to pumping up the A/C pumped this afternoon. She works great and that Delphi HT6 compressor is so quiet you don’t even hear it run. It’s in the upper 90’s here today and she was blowing 54 degrees out of the vents cruising down the highway. 54 really feels cold when it is almost a 100 ambient. It will freeze you out after a while. Next 2 projects is to get it back to the tuner so they can straighten up their tune to take out the parking lot idling hop and the piss poor cold start open loop operation. After that it goes back to the exhaust shop to have some rework done on the exhaust as I cannot stand the way it sounds. Going to have a dual inlet dual outlet Magnaflow x-muffler installed and move to true dual exhaust instead of the huge restriction it has now where it is squeezed down to a single pipe for 3 feet.

 

[Larry]

Oh, I forgot to post up the official decal to consummate the 8.1L install :costumed-smiley-007

And a few shameless glamour shots

 

[NMC_EXP]

Larry

When you get tired of the 8.1L what's next......a V12 Allison aircraft engine?

Love the Burb, by the way. Got my eyes peeled when I'm blowing thru Pueblo West but have not eyeballed it yet.

 

[Larry]

Larry

When you get tired of the 8.1L what's next......a V12 Allison aircraft engine?

Love the Burb, by the way. Got my eyes peeled when I'm blowing thru Pueblo West but have not eyeballed it yet.

for sure! Nah, I think the 8.1L will keep me under control for a while although I would love to get my hands on a PSI 8.8L for the K10. Those 8.8L’s are turning 565 lb. ft. of torque at 1800 RPM. I drove a 71 passenger school bus last week with an 8.8L and it had better low end grunt than a Cummins ISB…..no waiting on turbos to spool up. They just go!

I’ll look you up next time I’m up in Canon. You may see the Burb on Hwy 50 sooner or later as I am constantly on Hwy 50 running back and forth between McCulloch West and town.

 

[1stDeuce]

Nice work!! Well, my quest for an 8.1L is over. I settled. Found a 2002 GMC K2500 with a 6.0L Auto for too good a price to pass it up. It'll do. First project is to ditch the contractor box for a flatbed.

Just curious, but did you do the A/C plumbing, or have someone do it? I will eventually need to get A/C on the Comanche functional, and I'm not sure how exactly to go about getting it plumbed up... Custom hoses will definitely be required...

And from an engineering standpoint, I can't see how the clutch reservoir makes a bit of difference... It only needs a tiny volume of fluid... ?? Still think it's so much better, and not just better because you bled it??

Thanks for keep us all envious!
Chris

 

[Larry]

Nice work!! Well, my quest for an 8.1L is over. I settled. Found a 2002 GMC K2500 with a 6.0L Auto for too good a price to pass it up. It'll do. First project is to ditch the contractor box for a flatbed.

Just curious, but did you do the A/C plumbing, or have someone do it? I will eventually need to get A/C on the Comanche functional, and I'm not sure how exactly to go about getting it plumbed up... Custom hoses will definitely be required...

And from an engineering standpoint, I can't see how the clutch reservoir makes a bit of difference... It only needs a tiny volume of fluid... ?? Still think it's so much better, and not just better because you bled it??

Thanks for keep us all envious!
Chris

Nothing wrong with that. 6.0L’s are great engines as long as you don’t tow too heavy in high altitude they’re fine. I had a 2005 Silverado HD with a 6.0L that I fixed and flipped a few years ago. It ran great but didn’t do any better on fuel economy over my 2001 Silvy with the 8.1L. In fact, the 6.0L drank more fuel with the car trailer behind it. The 6.0L, especially backed by an auto trans, was much more athletic to drive around town. Pretty quick truck actually.

Yes, I did the A/C hoses myself at the local Napa store. I’ve known these guys my entire life where they let me use the tools to build the hoses. Building hoses is a lot easier than one would think. Finding all of the compatible fittings is the hassle.

As far as the clutch reservoir, no I don’t think the reservoir itself made any difference. What made the big difference was replacing the master and slave and spending more time adjusting the push rod between the slave and clutch fork. On these type hydro clutch systems I actually bleed the systems off the truck and on a bench. The bigger reservoir is just cheap insurance for keeping the fluid cool when working the clutch pedal a lot. I’ve noticed on my K10 with the exact same hydro clutch arrangement the pedal starts getting harder and harder as you work the pedal more and more. Last month we spent a week in Canyonlands. After riding the trail for a few hours on and off the clutch pedal, the pedal gets pretty stiff. Added capacity for fluid cooling is my “engineering” standpoint on the larger reservoir

. The original clutch reservoir is way too small in my opinion. I ordered two of these Tilton reservoirs so the other one is going on the K10 when I get some time abliet that one is a bit smaller. I had ordered a 10 oz and I think an 8 oz. The bigger reservoir ended up on the Burb because that is the box I pulled out of the parts bin first

 

[justcuz]

Larry,
You get your open loop cold start situation fixed yet? Curious to see the fix on that, recalibrate the IAT settings maybe?
The Polar Bear is looking real nice. Just about done right?

 

[Larry]

Larry,
You get your open loop cold start situation fixed yet? Curious to see the fix on that, recalibrate the IAT settings maybe?
The Polar Bear is looking real nice. Just about done right?

Nope, it goes back to the tuner the week of the 13th to straighten out what they should have done right the first time. Dealing with “tuners” is aggravating.

 

[justcuz]

Dealing with a lot of people in the automotive repair and modification industry is frustrating. That is why I do most everything myself and read the internet sites like this one related to my interests. I also search YouTube videos for assistance. Yelp or other sites help to find feedback on services for things I can't do myself.
You are pretty much the complete do it yourselfer also so I know I'm preaching to the choir here. Hope you get it worked out to your satisfaction.

 

[Larry]

Dealing with a lot of people in the automotive repair and modification industry is frustrating. That is why I do most everything myself and read the internet sites like this one related to my interests. I also search YouTube videos for assistance. Yelp or other sites help to find feedback on services for things I can't do myself.
You are pretty much the complete do it yourselfer also so I know I'm preaching to the choir here. Hope you get it worked out to your satisfaction.

Exactly, but when it comes to tuning that is something that really needs to be left up to the “pros”. I already went through phase where I did my own tuning when I was running the 8.1L in the K10 on a RamJet/Marine MEFI-4 ECM for the first year. The MEFI system is based on a speed density calculations opposed to Mass Air Flow, where you need to tune all of the tables for EVERY event (temp, MAP, load, etc.). I quickly learned that tuning is something that is hard to get really good at by just doing one engine. Tuning a manual trans vehicle on speed density is really time consuming with lots of trial and error. Tuning is an art that gets honed by doing it A LOT! Then when it comes to OBDII the tuning software is super expensive (like $800 on up). I just don’t see buying that tool is worth the investment for one single truck let along the experience in knowing what you’re doing as mentioned above.

I think the lesson learned here is what we’ve all known all along……leave the engine stock as possible. I moved the K10 from MEFI-4 to a Howell harness running a production truck P59 ECM just like any other 8.1L truck ( & early LS engines) but that 8.1L is box stock. I plugged that Howell ECM (with their in-house 8.1L “hot tune”) in back in 2009 and have never had to touch it since. It just started right up and been running great for 6 years and 35,000 miles with no odd ball drivability abnormalities like the Suburban currently has. The difference…. The aftermarket camshaft in the Burb that requires hands on live tuning. I won’t tolerate the drivability issues on the Suburban for long so when I run out of patience with these so called “tuner pro’s” I have no qualm about yanking this cam back out, installing a stock cam and running it on the same calibrations that are in the K10. If I lived on Phoenix, Texas, Detroit or California where really good tuners exist I feel this would be a much easier task in getting the tuning quirks worked out of the Burb but in Colorado….not so much.

 

[chilliwak]

Wow Larry. I really did not know there was that much work involved. No wonder I am still old school working with what you call toilet bowl carbs.... All jokes aside at least I can still figure that stuff out. Hope that fine rig treats you well. I can only dream of having a nice `Burb´ like yours! :drool:

 

[justcuz]

I hear you on the investment in equipment for just a couple vehicles.
Cams can be changed but the profiles have to be modest enough that there is no overlap we used to get with the old lumpy cams. That kind of overlap can't play well with the computer programmed engines that have cleaner operating parameters built into them. Stock cams will obviously work well, but you may be able to increase the lift/duration a bit over stock. Plus another cam change will require another retune correct?
This is why lobe separation angles are so wide on new cams, it eliminates the overlap that causes confusion with the downstream O2 sensors. That and roller cams that can ramp faster. You can actually have some pretty high lift and duration numbers do to the faster ramping of the roller cam, yet with the wider lobe separation angle you lose the overlap.
With overlap you are getting dilution of the intake mixture because the exhaust valve is hanging open slightly on the intake stroke. Kind of like an EGR valve only worse. The cycle of intake, compression, power and exhaust with a large overlap cam at low engine speeds causes a consistent drawback of exhaust on the intake stroke causing the lumpy idle, low vacuum readings and lean mixture. A computer controlled engine with O2 sensors will read this as a lean exhaust and add more fuel, then the excess fuel may not all get burned in the combustion process so the O2 leans the mixture. It becomes a viscous cycle and causes all kinds of running issues. Thats why computer controlled engines don't like overlap.
The O2 sensor is designed to do exactly what it is doing reading the exhaust and changing rapidly but the overlap is what overpowers the O2 sensor to work effectively.
This is kind of a Cliffs notes on cams and overlap, there's a lot more to it, but you get the idea.
In open loop when cold, the O2 sensors don't read the mixture, as I recall it is a function of the IACV and increased engine speed.