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6.2 or 6.5 diesel versus 350 V8Tbi. Out of which diesel engine is better than the 350?

I have had multiple GMT400 trucks with turbo 6.5s and NV4500 and I have to say that is the tranny that should be behind them , really wakes them up .

Especially compared to a power and mileage sucking TH400 it maybe stout but with its tall first ,no lockup , and lack of overdrive it just uses up to much valuable fuel and power
 
diesel4me said:
The 6.2 has power & torque more like a 250 or 292 straight six than a 350 V8 in my opinion--they only make 140 HP and the torque is nearly identical ,and peaks at low RPMs much like a straight six does (about 1600 rpms)...

Both of my 6.2's never broke 20 mpg more than once or twice..to me they are not really much more economical in the long run,with diesel costing more than gasoline..and today's EFI V8's will get better mpg than that..the diesel does have the advantage of not needing a tune up,no plugs,wires,cap & rotor,but glow plugs do fail and are around 10 bucks each..

Google "6.2 reliability" and you'll find 1000+ posts varying from "mine is running sweet with 500K on it ",to "they SUCK,the cranks snap like glass,they are noisy,eat injector pumps,blow head gaskets,etc"..all depends on who you ask,and how good or bad their luck is..

A gas 350 will leave a 6.2 diesel powered truck in the dust in a standing start 0-60 race...while a 6.2 might tow a light load OK,I would not want to use my truck for towing--trying to get it up to 65 mph empty when merging onto a highway is scary enough !--especially if its an uphill grade..
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I take exception to damn near everything you have said here, my experince with these engines has been in cold climates Of the Arctic all the way to heat of the Desert

Glow plugs rarely if ever fail when treated right I have had close to 15 or so of these trucks that I have actually put miles on (not to mention countless parts trucks) and of all those trucks I have had to replace maybe 2 sets of glowplugs .

Even in N/A form They have more power and tourqe then any FACTORY carbed truck 305/350/400 small block and the Turbo motors will standup and walk away from a TBI350

Diesel fuel is now back to being cheaper then gas just about everywhere now (the way it should be) combine that with double the mileage and lower cost of maintenance (and purchase price since everyone hates on these engines you can get good runners for free sometimes) it would not take long to pay for a swap

Towing, I have put some serious weight and grades behind these trucks and while they are not a cummins or dmax they will get the job done with proper gearing ,

Turbos are a game changer and GM should have never offered these engines without one....... Actually boost period is a game changer .there are some guys playing with roots and centrifgul style blowers with good results .

This little guy here gets 25 mpg and merges with ease and can cruise 75-80 all day long with the A/C on . And its exactly the way GM built it in 1983

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Yah my burb will do 80 mph freeway speeds without alot of issue. It's as stock as they come.

Acceleration is like a freight train. It happens slow but it does happen and keeps happening till you reach top speed. Which on my burb seems to be 87 lol.

I have driven turbo 6.2s a couple times and I would say they would stay with a mildly built small block. I bet my burb would stay with a 305 powered burb.

I think my comfortable tow limit is about 5000 lbs. My Jimmy when on 35s could roll out about 65 no problem with that. 7000 lbs was pushing it stupid hard never even got to 60. But remember that's a lifted Jimmy. I have towed say 3000lbs with the burb and it tows better than my Jimmy does. I would tow 8000 lbs with the burb and not bat an eye. It would be slow and probably limit it to 60 or 65.

Around here diesel is still more expensive than gas so the Jimmy will probably end up with a 5.3 I will lose 3 mpg outright but it will cost almost the same. Our gas is usually 20cents cheaper than diesel. Not always but most of the time.

The burb will get a turbo.
 
blackandgold51 said:
Keep in mind that i dont drag race and not in the driving fast thing. Although i would like some decent accelration, ive heard you can add a turbo to the diesel motors
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This is exactly why I think the 6.2/6.5 would be a good fit for your purpose. Most of the limitations with these engines (like cracked mains and overheating) are things that non-drag-racers typically don't encounter.
 
campfire said:
This is exactly why I think the 6.2/6.5 would be a good fit for your purpose. Most of the limitations with these engines (like cracked mains and overheating) are things that non-drag-racers typically don't encounter.
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Wonder how difficult it is to install one in mines that has a 350 tbi
 
If you want economy in one of these trucks, it is that simple, diesel. Nothing you do mechanically to a 350 is going to increase mileage exponentially unless something is already wrong with it. Don't waste money trying. Make sure it runs correctly, that is all you can do. You can add parts to increase power, but very few things will increase economy without requiring more fuel, and they are complex and costly (roller camshaft and rockers). Even then it won't amount to much in the grand scheme, except spent money.

If you can live with anemic performance, I don't see why any of the 6.2/6.5's wouldn't suit you, turbo or not. Obviously a turbo variant doesn't have much in the way of downsides, but if someone is yanking a perfectly good NA 6.2L out of a truck and you can get everything for $200, that would be hard to pass up.

Have to be careful worrying about economy though...you can spend a lot of money to save money, and you have to figure out the cost of adding those MPG's and whether or not you will ever break even. Your time too, if you use that as a factor.
 
dyeager535 said:
If you want economy in one of these trucks, it is that simple, diesel. Nothing you do mechanically to a 350 is going to increase mileage exponentially unless something is already wrong with it. Don't waste money trying. Make sure it runs correctly, that is all you can do. You can add parts to increase power, but very few things will increase economy without requiring more fuel, and they are complex and costly (roller camshaft and rockers). Even then it won't amount to much in the grand scheme, except spent money.

If you can live with anemic performance, I don't see why any of the 6.2/6.5's wouldn't suit you, turbo or not. Obviously a turbo variant doesn't have much in the way of downsides, but if someone is yanking a perfectly good NA 6.2L out of a truck and you can get everything for $200, that would be hard to pass up.

Have to be careful worrying about economy though...you can spend a lot of money to save money, and you have to figure out the cost of adding those MPG's and whether or not you will ever break even. Your time too, if you use that as a factor.
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Are the any computer issues ihaveld have to deal with while installing a diesel in thr suburban in placr of the tbi 350? The suburban is a 1990 by the way
 
blackandgold51 said:
Are the any computer issues ihaveld have to deal with while installing a diesel in thr suburban in placr of the tbi 350? The suburban is a 1990 by the way
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Probably need to hear from other folks that have done the swap, but this is where having a complete donor comes in...probably best (not sure about easiest) to replace the entire harness. Problem with that is, you'd want the same year and model, along with matching rpo's, like power windows, door locks, etc. There will be so much mechanical to change, I'm not sure swapping harness would be that difficult all things considered.

I don't know what all instrumentation specifically the diesels got, but the oil pressure gauge was 80PSI, there was a wait light IIRC, and there was a water in coolant light, among other things I'm probably missing.

Two options for speedometer: need to run the same transfer case and somewhat separate the speedometer wiring from the ECM, but that's not too tough. Or, swap to an earlier cluster that ran a mechanical speedometer, and swap transfer case as well. The 241 you have is a great t-case, I'd rather keep it and the electric speedometer than go backwards.

Computer is irrelevant with the diesel. I assume ABS can be kept, but no idea how all that braking stuff works. Hydroboost with ABS?
 
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Again, I am in for the info you guys are sharing.

PMD just shot crap last week, so I am back to getting 14mpgs for now. New PMD ordered. I was getting 17.5 on a couple tanks before the PMD pooped on me.
 
GWeakland620 said:
Again, I am in for the info you guys are sharing.

PMD just shot crap last week, so I am back to getting 14mpgs for now. New PMD ordered. I was getting 17.5 on a couple tanks before the PMD pooped on me.
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I think a lot of folks told you that was coming... :doah:


Hahahahahaha. :pimp:

What symptoms did you have?
 
blackandgold51 said:
Pmd? Dont know what that is
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The pump mounted driver is a basic electrical controller used in 94 and newer 6.5 engines. It has a cooling issue in stock configuration and ages faster than the rest of the engine. This issue is super easy to prevent, and I'm making fun of Greg because 2 months ago he said it wasn't worth preventing. He opted for laziness (as we all do sometimes), and IMO it but him this time.
 
Pump Mounted Driver, it's a computer/module mounted on the engine. They are know for going bad, and causing some odd symptoms. Usually will cause check engine lights, stalling/sputtering, and starting issues. Easy to change.
 
Most of the 6.2s that I had got amazing mpg. Had one 84 that was turbod in a 3/4 ton burb with a 700 that would almost always AVERAGE 20 or better. All of the other ones I had (that had OD) would average about 16 but still pull 20+ on the highway. Had a 90 that I went from 700r4 to th400 and average dropped from about 16, down to 12 and highway mpg went from 20ish to 15.

Went on a road/offroad trip with a friend in his identical everything tbi 350 burb, and me in the turbod 84. I used very close to half the fuel he did at every fill up.
 
black dawg said:
Most of the 6.2s that I had got amazing mpg. Had one 84 that was turbod in a 3/4 ton burb with a 700 that would almost always AVERAGE 20 or better. All of the other ones I had (that had OD) would average about 16 but still pull 20+ on the highway. Had a 90 that I went from 700r4 to th400 and average dropped from about 16, down to 12 and highway mpg went from 20ish to 15.

Went on a road/offroad trip with a friend in his identical everything tbi 350 burb, and me in the turbod 84. I used very close to half the fuel he did at every fill up.
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Fuel price here in new orleans like for unleaded 4 example is 1.83 a gallon for gas while diesel is around 2 something.

So i think i might be alright with a diesel. Just need to know the basic steps on how to install one in my gasser and since i sometimes get tired of filling up and want to keep my suburban(especially since i made somemodifications to it). I sometimes see 6.2s for around 400 bucks online. Not bad however i sometimes wonder why so cheap?
 
Compared to modern engines, a 6.2 is slow. Even a 6.5 won't keep up with a modern tow rig. Efforts to modify the engines to increase power often lead to reliability headaches (You can't beat on these engines like you can beat in a Cummins). So folks wanting to tow won't touch them. And folks not towing usually don't buy diesels (in this country, at least). That's why they're cheap.

If you're not trying to tow a car hauler up Veil pass at 80mph you will be fine.
 
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