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One Piece at a Time: My 1985 Diesel Suburban

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AgDieseler said:
I just ordered a new 6.5 Optimizer. It will be here in about three weeks.

This is not the right time to start a Duramax swap. That's a planned project, and I'm not going to confuse it with what would become an opportunistic repair during a very busy year of deliverables for the business. In more detail, the engine cage and rear subframe are tailored to the dimensions of the 6.2/4L80E/Magnum-205, and it's all pretty tight. I'm 100% disinterested in remaking the bulk of that tube work. Fresh Detroit power makes this a bolt in affair, and gets me back on the trail delivering on commitments in a relatively short period of time.

Now, the newest version of the 6.5 has significant upgrades that make it very desirable all on its own. At a high level, they built a block and head and crank that will run 350hp/650lb-ft all day. That's plenty for my purposes. The no-longer-in-production P400 has taken that further (incidentally, I did find a couple of them still available, but I'm not spending that amount of coin for anything other than an LBZ swap). In more detail, the engine I ordered has an improved metallurgical cocktail, webbing and wall thicknesses are increased, heads have a handful of cooling and durability upgrades, it's got all the nice oil spray stuff, and has the same large diamond prechambers that I ran in my 6.2. Turns out. GEP opted to stop using old cast cranks alongside the P400 forged ones, and just settled on the forged piece all around, so these later style Optimizers enjoy that forged bottom end. Pretty nice little upgrade, and all my fuel injection stuff will swap right over. It's almost like GEP now makes the engine that Detroit originally designed over 40 years ago (and GM would go on and cheapen to suit its own needs).

When it gets here, my dad and I will blow it apart, balance the crank, rods, pistons, and flexplate, install a gapless compression ring, stud the heads and mains, install my timing gear set from the 6.2 (assuming it survived), install some other baubles and bolt ons, and get it all back in place. New oil coolers, flushed hoses and lines, turbo health check, clean out the intercooler, and all that prep gets underway, soon. Our friend, @Greg Ducato, agreed to look over the 4L80E while it's out as a good "sniff test."

I'll probably even run back over a few engine cage welds that were really hard to get to, and do a bit of frame reinforcement while I have access. I mean, I might as well. Maybe I spent too long at @Greg72's last weekend.

Time to get to work.

David
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Ouch, did you pay $8500?
 
My BIL had 93 sub with a 6.5 over 600 thousand Klms on it when he sold it. Never any engine faults that I know of. We have had many 6.5s over the years when they were popular, some not so stellar. But nothing that couldn’t be fixed way cheaper than a duramax.

I know the cost of Duramax repairs.
 
imiceman44 said:
Ouch, did you pay $8500?
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Ballpark.

max 02 said:
But nothing that couldn’t be fixed way cheaper than a duramax.
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Seems like the 6.5 continues to be a high value platform.

Fastereddie said:
Sounds like a solid plan. Any idea what the power difference will be?
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With a pump change, I bet 550 lb-ft is my practical limit while staying all mechanical. I’ll start by just moving my fuel system over as-is. After break in, it won’t be long before I turn up the fuel.

KirsL said:
I think you'll be plenty happy with the new GEP engine.
Going for the bolt in swap is definitely the smart move as you'll be up and running in no time.
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I’m really excited. The forged crank is what sealed it for me, and taken together with the rest of the improvements made this a good value purchase.

David
 
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ZooMad75 said:
He’s the guy that taught both of us how to correctly time the injection pump on 6.5’s with a sonic tool.
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AgDieseler said:
So neat! That's a fine art. I time with a luminosity probe, and there's still quite a bit of "test and check" to it.

David
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Do either of you guys have a written procedure for this? I have mine tuned via the ear method, and I don't have a very practiced ear. I timed and retimed the Blazer engine a dozen times or so before I realized the timing kept changing because the IP was failing. Once I swapped that I set it by ear and never touched it again. Same for the burb. It runs fine, but it may or may not be very close to correct timing. :dunno:

The official instructions I found were to run it on a dyno and tweak it until maximum power was achieved. But that's not a practical or repeatable shade-tree method.
 
The 6.5’s we were working on were the computer controlled versions. I don’t have access to the procedure now. But there was added steps that involved setting the timing offset in the pcm. The pump was installed to the 0 degree mark and the pcm takes over from there.
 
campfire said:
Do either of you guys have a written procedure for this?
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Not really. The instructions for my MT480 meter explain how to do it, but not the target spec.

Timing at idle isn't really that helpful since the pump has an advance built into it. I time at 1500 and 2000 RPM (when the advance is off), and set it for 1 - 3* after TDC. Do all this with a hot engine, and I use rolling 5-60 MPH runs to determine what the engine likes. I've never timed an engine BTDC (but it's an efficient way to destroy stuff), and I always start with the timing marks in line. My 6.2 was timed at 3.5* ATDC at 2000, and the marks ended up being just slightly offset to the passenger side.

This is somewhat of an approximation, because the timing needle jumps 1/2*, but never went past 3.5. Recall, this is combustion timing, and not injection timing.

David
 
AgDieseler said:
Not really. The instructions for my MT480 meter explain how to do it, but not the target spec.

Timing at idle isn't really that helpful since the pump has an advance built into it. I time at 1500 and 2000 RPM (when the advance is off), and set it for 1 - 3* after TDC. Do all this with a hot engine, and I use rolling 5-60 MPH runs to determine what the engine likes. I've never timed an engine BTDC (but it's an efficient way to destroy stuff), and I always start with the timing marks in line. My 6.2 was timed at 3.5* ATDC at 2000, and the marks ended up being just slightly offset to the passenger side.

This is somewhat of an approximation, because the timing needle jumps 1/2*, but never went past 3.5. Recall, this is combustion timing, and not injection timing.

Daless.
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I always timed mine by ear. Current setup is running about a 1/16 advanced. Seems pretty happy there. Egts are good and smoke is minimal once the turbo spools.
 
ZooMad75 said:
Did you find the arp head studs you were looking for @AgDieseler ?
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Not yet. I did order a backup from Gator Fasteners (same alloy material as ARP, just a very new brand), but I'll use a set of ARPs if they come along.

If my dad and I are going to crash EJS properly, we need a running suburban. Also, we're doing a big and very remote trip in June for one of the brands, and I need to get enough proving miles on the setup to be comfortable going way out there.

David
 
Okay, so here's the rundown on what's coming together:
  • 6.5 will all the fancy new forged stuff running 20.2:1 (about the same as how my 6.2 was setup)
  • New DB2 injection pump rated for 250hp (which is about 520 lb-ft at the 1800-2000 torque peak)
  • New Bosch higher pressure injectors with the full flow nozzle (no metering needle)
  • I sprang for new injector lines while I was at it
  • New FASS lift pump and filter system, because @KirsL made it look so sweet
  • Head studs and main studs
  • 1.6 roller rockers
Once it arrives, it'll get blown apart (in a good way), and:
  • get balanced - I'll take it to the same race shop that balanced the 6.2 way back in 2001, and they'll put their hands on everything in between the balancer and flexplate
  • send the secondary compression rings to Total Seal to be made "gapless"
  • I'll port match the heads and manifolds
  • transfer over my timing gears and 6.2 front cover
  • move the darned turbo oil drain down to the side of the oil pan
  • move the tach from being crank triggered to a new ESS on the oil drive
  • make up a small set of "steam lines" similar to LS engines for the back cooling passages where the heads tend to heat soak at #7 and #8
I haven't been this excited about engine stuff in a long time. My bank account isn't thrilled, but at least I'm smiling from ear to ear.

David
 
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Be careful of the cam drive tach sender. If it is the one that came factory on the California trucks that is. I bought a used one because the new ones are crazy high. It leaked oil. I bought another used one with the same result. My tach signal comes from my alternator now. Just wanted to warn you.
 
Barrman said:
Be careful of the cam drive tach sender. If it is the one that came factory on the California trucks that is. I bought a used one because the new ones are crazy high. It leaked oil. I bought another used one with the same result. My tach signal comes from my alternator now. Just wanted to warn you.
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I'm just switching from the old style pump drive that has a vacuum pump on the top of it to one with a hall effect sensor. Same same, really. I guess I could take the signal from that fourth prong on the alternator, if needed. Good thought.

Babaganoosh said:
Somehow you make me want a 6.2 or 6.5 cause you can hot rod them and no one does it.
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It's exposure therapy.

David
 
You need the Dakota Digital converter for the 4th alternator wire. Thankfully it is adjustable. The MT1480 really makes that easy and accurate.
 
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