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MetalMan
07-07-2006, 09:24 PM
GIVE ME THE DIRT, I want to know everything about these things, I know the 5.7's were modded Olds engines and were basically garbage. But that's all I know about old GM diesels. What's the skinny on the 6.2's?

little laker
07-07-2006, 09:40 PM
I haven't heard too many good things about them.

They're definately underpowered

However I'm using an 85 in my project, and even though it has a little over 500,000 km on it the bottom end was never touched until now.

The bearings were in excelent shape when we changed them the other day, and the motor still runns like a charm.
I thought that it was re-built once until we looked at the date stamped on the bearings.

I firmly believe that they're good motors as long as you stay on top of the maintence. My plans include only running synthetic oils so I'm sure that the engine will make the million MILE mark.

One thing going for mine is I know that I know the mechanic that worked on it it's entire life. It started off as a mill truck and was sold to a local man who kept bringing it to their #1 mechanic in his off time. And he always does everything right.


They used the big brother (6.5L Turbo Diesel) in the Hummer H1 until a year or 2 ago so how bad can the motors really be.

MetalMan
07-07-2006, 09:46 PM
Yeah the lack of power is one thing I was aware of, I'm also interested to find out what there is for aftermarket "improvements". Mainly I'm worried about reliability though. There is a chance my next bush beater could have one of these mills, I want to know all I can before I go check it out tomorrow. BTW anyone know if an '85 3/4T is supposed to have a D44 front and 208 T-case? Because apparently this one does...I figured it would be 10-bolt and 205.

little laker
07-07-2006, 10:42 PM
Mine's a 1/2 ton, so I can't compair diff's I think that mine's a 10 bolt front, and know that it's a 12 bolt rear.

Bigger injectors, however this only works if the injection pump is strong enough.

The air intake ends at the firewall, and looks like it sucks the hot ait from the rad. in my opinion drilling out the firewall in this location will also get you a little more power with a little bit of a ram air effect.

Propane injection will even give non turbo Diesels a power increase.
more on that here. http://www.mrsharkey.com/lpg.htm

You'll find out more on the 6.2L here
http://www.gm-diesel.com/
I'm just 4 fun there

u2slow
07-07-2006, 11:14 PM
My DD is a 6.2L Suburban.

The 6.2L is fine one you eliminate the stock GP controller and fuel filter contraption. Those 2 alone cause no end to hard starts and the resulting dead starters & batteries.

If the rubber deteriorates on the crank balancer - change it sooner than later.... or you might be shopping for a crankshaft too.

A fuel additive is supposed to make the IP last longer on these older diesels that use the rotary IPs. The reason being sulphur used to provide IP lubrication, but they're refining almost all of it out of the fuel now. I've also heard Husky's 'DieselMax' fuel already includes this type of additive.

'85 3/4-ton will have a 10-bolt and NP208 stock. I hope it has a manual because the TH400 kills any of that diesel economy you are looking for.

The turbo from a 6.5TD is adaptable - requires the 92-93 wastegate. IP would need to be retuned for max benefit.

Propane works too... http://www.members.shaw.ca/k2pilot/Propane%20article.html (http://www.members.shaw.ca/k2pilot/Propane%20article.html)

little laker
07-07-2006, 11:46 PM
My 1/2 ton has a TH700. I don't know if this is normal.

What do you recomend to use as a fuel filter u2slow?

I'll have to change my crank balancer before I go to far. It's easy now, and I just saw a 6.5L with a broken crankshaft at the wreckers. Probably caused by this.

Thanks man

MetalMan
07-08-2006, 09:49 AM
Sweet, awesome info guys, Thanks! Keep it coming. He did say it was stick, not auto. I just want it for a bushbeater, actually that's all it's really good for. I'll check out those sites

ottoman
07-09-2006, 04:12 PM
guttless and slow but can be reliable. timers for the glow plugs can be a problem resulting in hard starts . make sure the starter still has the front support attached . both 6.5 and 6.2 blocks are famous for cracking in the webbing inside the block and 6.5 heads are junk . banks makes performance stuff for them and if you get a good one , even though it will be slow no matter what you through behind it , it will be hard to make it go slower.

1_ton_k5
07-09-2006, 10:15 PM
I swapped a 6.2 into my Jimmy and couldn't be happier. First of all it's not really that slow...it accelerates about the same as the stockish 350 I had in there before. The number one reason they got a rep as being slow was the stupid gearing GM used in 6.2 trucks. 2.73's, and 3.08's were common even it truck with the 700R-4.

I have a SM 465 behind my 6.2 now and it does just fine with 4.56's and 39.5's.

As it sits now it gets a steady 19.5 mpg on the highway, almost double the mileage the 350 got.

6.2 trucks with overdrive usually get 25-29 mpg.

For rock crawling and stuff the 6.2/465 is wicked. The redline is governed by the injection pump, but so is the idle speed. If you try and pull the rpm's down it'll add fuel. The result is that in the technical sections I often wheel with both feet flat on the floor. I have never had it stall in low range yet, honestly I think it'd smoke the clutch before it'd stall. It'll also run at any angle without the slightest sputter or stumble. If it could maintain oil pressure it'd run upside down.

Balancers are a known problem, and some 6.2 blocks do get the spiderweb cracks. The biggest reasons they can get a bit of a bad rep is hard starting and being confused with the 5.7 diesel.

There are performance parts for the 6.2, gear drive timing sets, stud girdles for the bottom end, headers, ceramic coated lower compression pistons, and of course turbo kits.

Mine has 362,000 km on it and still runs like a champ. I have manual control GP's, AC 60G glow plugs, run a spin-on fuel filter and a Racor filter/water seperator, and port matched my 'J' code intake. I also have a set of Hummer H1 headers for it...they may go on soon.

One last benefit in my opinion is that slow crawling and a lot of idling will cool down a diesel rather than spike the temps like most gas engines do. A diesel uses such a small amount of fuel at idle that it can be hard to warm them up. On a hot summer day I had to stop on hwy 1 because of a major accident...we sat there for about 30 minutes and I watched my temp gauge slowly drop from 200 F down to 140 F before we started moving again.

Only downside is aircaring a NA 6.2 with a wide ratio manual tranny can be entertaining. The test is 4 minutes long simulating a lot of different conditions. The end of the test is a WOT pull from 12km/h to 95 km/h. That isn't gonna happen using one gear, and with those useless fucks at aircare not knowing how to drive my truck failed a few times. It's too easy to shift early and then floor it and make it puke smoke.

I installed a throttle stop limiting WOT to 65% of max and it passes with flying colors every time now. I intended on that being a temp fix to pass aircare, but found that i never use more pedal than that anyways...so I left it.

Ooops, looks like I wrote you a novel. [1b]

Rene

MetalMan
07-10-2006, 04:46 PM
Cool, good info, what year was your 6.2 out of? Also, what's it based off, SBC or Olds?

little laker
07-10-2006, 05:06 PM
1_ton_k5, if you don't mind me asking how did you handle the wiring?

I'm thinking of using the stock Blazer wires for 90% of my project, but bolting in the 6.2L fues box for the engine stuff. But there has to be a better way.

tenpack
07-10-2006, 07:25 PM
i've understood the 3/4t's has athe J-Code engines where are more deisrable from the C-code( if i remember right) and that a 1/6th of a turn on the injection pump combined with a free flowing intake with good filter will yeild good power. And supposedly the intakes have shitty port matching resulting in bad flow. Off ck5.com

1_ton_k5
07-10-2006, 08:02 PM
1_ton_k5, if you don't mind me asking how did you handle the wiring?

I'm thinking of using the stock Blazer wires for 90% of my project, but bolting in the 6.2L fues box for the engine stuff. But there has to be a better way.

I bought a complete running POS '83 1 ton 2WD pick-up with a 6.2. I didn't use the motor though. I bought the donor for every other part of the swap. Wiring, hydroboost, rad, rad mounts and shroud, oil cooler lines, battery trays, diesel dash, filter mounts and Racor mount, plus all the dickshit stuff you can never find. The motor itself I got from an '85 K20.

I had a few other projects on the go at the same time, one of which was swapping my AC crap (that didn't work) for non-AC controls. The donor was non-AC. I swapped the engine bay wiring harness from the donor to my truck, as well as the under dash stuff. Pretty much anything that was different got swapped. The headlight wiring as well as the wiper wiring is all the same though. The wiring can be split at the square junction block on the firewall. The lights/wipers/etc are one part, and the rest is the other part.

You can do the wiring yourself, but it's gonna be a lot more work and head scratching. Using a donor makes it all plug and play.

Cool, good info, what year was your 6.2 out of? Also, what's it based off, SBC or Olds?

My 6.2 is an '85 model from a K20

The 6.2 was designed and built from the ground up by Detroit Diesel for GM. It isn't based off of any gas engine at all. It shares no parts with any other gas engine either...

i've understood the 3/4t's has athe J-Code engines where are more deisrable from the C-code( if i remember right) and that a 1/6th of a turn on the injection pump combined with a free flowing intake with good filter will yeild good power. And supposedly the intakes have shitty port matching resulting in bad flow. Off ck5.com

'C' code engines have an EGR deal that restricts the intake, only found on 1/2 tons. 3/4 tons and 1 tons got the 'J' code which supposedly has larger valves (I can't confirm that personally, but have read that in a few different places) and also has no EGR blocking any airflow into the intake. More air, more power.

Turning up the fuel rate on the IP will yield more power, but also higher EGT's and it'll be harder to pass aircare. With a manual tranny I have to use a throttle stop to get mine to pass, and my fuel rate is factory.

The intake port thing you read about was my intake. I'm tRustyK5 on CK5.com and the thread on intake port matching was mine. Yes, I found the casting on the intakes sucked, most ports needed almost .250" removed total to get them the same size as the gaskets (and the head ports)

Uber simple mod to do with a die grinder and a little time. It took me less than two hours to port match mine. I don't have dyno numbers and wouldn't even venture a guess as to power increase...but it was enough of an increase that I noticed when driving. Seemed snappier after.

Hope that helps...

Rene

u2slow
07-10-2006, 09:47 PM
I've gone through the wiring in my 6.2L to weed out tons of stuff that's just crap (GP controller, fuel filter doodads, AC, cruise, etc.)

From this experience I know there isn't much wiring that's critical for the diesel. I will homebrew it for my other rig when I put in the 6.2L. For the GPs you need a solenoid, a pushbutton, and an indicator lamp. The IP needs ignition power (to open the fuel solenoid). Anything else is optional.

I ditched my oil cooler and plugged the block. That was about 15,000km ago. Hydroboost is ideal, although you could see if the vaccum pump will provide enough for the regular booster (Ford and Dodge use vaccum w/diesel).

The stock diesel rad will work of course. Although you may be able to get by with the next size smaller (28x19?) if it has the thick core.

MetalMan
07-10-2006, 09:50 PM
Interesting...so there's no gas engine that bolts in, like the Olds diesels? Sounds like you know your stuff about these motors. I've wound up a little more strapped for cash than I thought, so I've got to wait on the rig I'm looking at, if it does go before I can grab it at least I'm learning something about 6.2 diesels!

u2slow
07-10-2006, 09:56 PM
While the 6.2L is not based on a SBC, it does use the same bellhousing pattern. :)

1_ton_k5
07-10-2006, 10:05 PM
It also drops right into the sbc motor mounts...

The good part about the swap is that it will pay for itself in a reasonable amount of time.

Rene

MetalMan
07-11-2006, 08:56 AM
I see...good to know. Certainly opens up options for either motor.

BeerBaron Sr.
07-13-2006, 07:32 PM
guttless and slow but can be reliable. timers for the glow plugs can be a problem resulting in hard starts . make sure the starter still has the front support attached . both 6.5 and 6.2 blocks are famous for cracking in the webbing inside the block and 6.5 heads are junk . banks makes performance stuff for them and if you get a good one , even though it will be slow no matter what you through behind it , it will be hard to make it go slower. This is a problem with ANYTHING that is'nt mantained
properly

BeerBaron Sr.
07-13-2006, 07:38 PM
Interesting...so there's no gas engine that bolts in, like the Olds diesels? Sounds like you know your stuff about these motors. I've wound up a little more strapped for cash than I thought, so I've got to wait on the rig I'm looking at, if it does go before I can grab it at least I'm learning something about 6.2 diesels!Any Chev V8 will bolt to a diesel set up