CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

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

So while I really like the 6.2/6.5 may I suggest an LS swap. It seems most are getting 15 mpg highway and about 12 in town. I have heard better and worse but I have kept close track and those seem to be a solid number. That's a 5.3 and it will leave any stock 5.7 in the dust.
 
So while I really like the 6.2/6.5 may I suggest an LS swap. It seems most are getting 15 mpg highway and about 12 in town. I have heard better and worse but I have kept close track and those seem to be a solid number. That's a 5.3 and it will leave any stock 5.7 in the dust.

I dont mind a 5.3 however do they last longer than the cast iron block 350? Which the 5.3 is all aluminum block and are they easy to work on?
 
Aluminum 5.3s are not common and they are expensive.

Most 5.3s are iron blocks aluminum heads.

They have lots o computer controls but not hard to work on at all
 
Lol i hear ya. just want to make sure i dont mess nothing up during the conversion

The biggest issues that I think you'll have are gearing and tranny. The diesel engine wants to maintain a lower engine speed than your current TBI rig. You'll also wanna change out your governor in the 700R4 or it will rev the diesel up to gasser speeds before shifting. Same for the torque converter, the gasser T/C has quite a high stall speed for a diesel. None of these things are mandatory, but you will have an unhappy 6.2 if you wind it up to 3000RPM between shifts. And an unhappy engine = crummier fuel mileage. You should still net a gain in mileage, but it won't be 25MPG unless it's geared well.
 
So while I really like the 6.2/6.5 may I suggest an LS swap. It seems most are getting 15 mpg highway and about 12 in town. I have heard better and worse but I have kept close track and those seem to be a solid number. That's a 5.3 and it will leave any stock 5.7 in the dust.

There are good reasons to consider an LS swap (power, dependability, etc.). But if mileage is the top priority, I don't think a 5.3 will ever catch up to a 6.2. Likewise, a 6.2 will never catch up to a 5.3 on the highway. :haha:

Designing anything is an exercise in compromise. You can agonize over this decision forever, or you can pick some option and GO DO IT! Which one do you think is more likely to deliver good results? :waytogo:
 
Yep very true.

Shoot now I have the burb maybe it's time for the Jimmy to have a big block.

@blackandgold51 remember all our milage numbers are from drastically different areas. I live at 6300 ft in the mountains. I'm pretty sure my burb is capable of 21 mpg at a lower altitude with less hills
 
So while I really like the 6.2/6.5 may I suggest an LS swap. It seems most are getting 15 mpg highway and about 12 in town.

Isnt that what most get with tbi 350s??

Last time I checked ours it was 12 in town and 14.5 on the highway at 70-75. I have considered a 5.3 in ours a couple times because the 350 is getting to where it is going to need some work. Just don't see one doing better (in a square burb) than a properly running tbi 350?
 
@blackandgold51 remember all our milage numbers are from drastically different areas. I live at 6300 ft in the mountains. I'm pretty sure my burb is capable of 21 mpg at a lower altitude with less hills

This is probably true. I'd be griping if I ever got below 20mpg in my worn-out, original 1/2-ton. But I live at 600' elevation in a place that's on the flat end of the spectrum. And I have gears that hate mountains.

Like I said, every decision is a compromise. What works for me does not necessarily work for Eric.
 
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

I have a '90 2wd 'burb. 6.2, th400. And no stinking computer! btw it gets ~17 mpg at 70. 285k miles on it.
 
Isnt that what most get with tbi 350s??

Last time I checked ours it was 12 in town and 14.5 on the highway at 70-75. I have considered a 5.3 in ours a couple times because the 350 is getting to where it is going to need some work. Just don't see one doing better (in a square burb) than a properly running tbi 350?

I have had a tbi 350s and they were 13 mpg max on the highway. 11 in town.

But if there is one thing this thread proves it is that the exact same rigs can get drastically different mpg.

5.3 seems like it will get 1 to 2 more mpg than a small block. But it will also give you a hundred horsepower over a tbi 350
 
blazinzuk said:
But if there is one thing this thread proves it is that the exact same rigs can get drastically different mpg.

Exactly. A lot of factors apply. I get 20-24mpg on a regular basis. My buddy has a newer 6.5 truck with the same tranny and pulls a consistent 14mpg. YMMV, quite literally.
 
I have a friend with a 94 6.5 burb that will not get over 13. Even a 2500 mile highway trip at 65 or less right at 13.
 
I had a long post in reply to some others here but it vanished when my fumbling fingers touched the "windows" button..:mad:..

To make it short,I do not hate my 6.2's,I just do not like some things about them...in my opinion they are no better on fuel than a good running small block,especially later fuel injected ones,and they seem underpowered for the size of the truck..(and the amount of cubic inches,you'd think a 379 cubic inch would rival a big block as far as power and torque,but it feels more like a straight six to me )..and I'm in a place thats at sea level,not a high elevation..

My pickup has seen its share of abuse plowing over 100 bad storms since I got it in late 2003,and I admit to not treating it well,I have even put used oil from a friends drain bucket at his shop to keep the oil level full for over a year,when the oil pan leaked pretty bad,and who knows what viscosity it was,or if it was synthetic,regular petroleum or if anything else like ATF was dumped in along with it ?..
I also did not change the oil for a long time,figuring I added so much so often it never had a chance to get dirty..

The engine seems no worse off for it,if anything it sounded quieter ,running it with "used" oil,though the oil pressure was somewhat lower ,especially in hot weather..now that I have patched the oil pan up and put fresh 15W-40 in it,the pressure is right back where it always was..

Despite having several glow plugs not working,it has started pretty reliably ,I had to jump start it maybe 3 times when it was below 15 degrees and the block heater was not plugged in...

My 3 sets of glow plugs over the past 15 years mostly failed from salt spray,the wire connector tabs rotted off,and the hex portion whittled away to nubs in 3-4 years..not many "died" electrically..

I also had a very tough time extracting the original glow plugs,one is still refusing to come out so I've just left it ,rather than break it off...
I also had one shatter while the engine was running,thought it spun a bearing it sounded so horrible..I'm sure that did that cylinder no justice..eventually I guess it broke up into small enough chunks to blow out the exhaust..

I have had 3 starters in it so far,two of the non gear reduction type,the current one is a gear reduction from a later 6.5..
Knowing these engines are noted for breaking off starter bolts and the engine block,I made sure to put the front brace on the starter,and always fear I'll find the outer bolt hole cracked someday..

For what is involved in swapping a diesel or LS engine into a square body,I dont think its a worthwhile venture really--though a 6.2 does "bolt up" with no real mods,there are about 30 other changes that you need to do to complete the conversion,as noted already--the fuel tank,sending unit,hydroboost brakes,and you will need a vacuum pump if you have a TH350 or TH400,plus change the govenor,torque converter,etc...granted if you have a donor truck its not that hard,but if you do not,hunting all these parts down can be difficult and costly..
You'd be better off buying a factory equipped diesel truck and put that on the road...

I rarely see any 6.2's here in salvage yards,the few you do find are usually junk,blown up,busted crank,seized,etc..if you do find a running one they want 500+ bucks in most cases...the ones sold at local government auctions might be "brand new" rebuilts in the miltary crates,or it might be one that was in Iraq full of sand and overheated,that was taken out,and washed off and put back in the crate....a big gamble,sometimes you luck out,other times you'll get boned..

Personally,if I wanted a truck with an LS gas engine,or a diesel, I'd just buy one that came factory with one and drive it...

I'm getting too old and physically unable to spend hours bending over under a hood,or lying under a truck any more,to undertake an engine or tranny swap...and its probable that 90% of the "backyard swaps" are at least somewhat "hack" and will never rival the factory's build and engineering..and I'm a guy who loved to rip out straight sixes and small blocks and stuff big blocks in everything too...

If I buy another old square body its unlikely I'd go for one thats a diesel..diesel fuel has been an average of 50+ cents a gallon more than gasoline here for decades--only in the past 6 months has it dropped to "only" 25 cents more..for what I do,mostly putting around town,plowing,going to the dump,and a rare "long trip" of 100 miles or so,I would just assume go back to gasoline...but for what I have put the 6.2 in my pickup through I cant bitch,its been pretty dam reliable..but I still never fully "trust" it...sounds like its going to come apart ,but hasn't so far..
 
I had a long post in reply to some others here but it vanished when my fumbling fingers touched the "windows" button..:mad:..

To make it short,I do not hate my 6.2's,I just do not like some things about them...in my opinion they are no better on fuel than a good running small block,especially later fuel injected ones,and they seem underpowered for the size of the truck..(and the amount of cubic inches,you'd think a 379 cubic inch would rival a big block as far as power and torque,but it feels more like a straight six to me )..and I'm in a place thats at sea level,not a high elevation..

My pickup has seen its share of abuse plowing over 100 bad storms since I got it in late 2003,and I admit to not treating it well,I have even put used oil from a friends drain bucket at his shop to keep the oil level full for over a year,when the oil pan leaked pretty bad,and who knows what viscosity it was,or if it was synthetic,regular petroleum or if anything else like ATF was dumped in along with it ?..
I also did not change the oil for a long time,figuring I added so much so often it never had a chance to get dirty..

The engine seems no worse off for it,if anything it sounded quieter ,running it with "used" oil,though the oil pressure was somewhat lower ,especially in hot weather..now that I have patched the oil pan up and put fresh 15W-40 in it,the pressure is right back where it always was..

Despite having several glow plugs not working,it has started pretty reliably ,I had to jump start it maybe 3 times when it was below 15 degrees and the block heater was not plugged in...

My 3 sets of glow plugs over the past 15 years mostly failed from salt spray,the wire connector tabs rotted off,and the hex portion whittled away to nubs in 3-4 years..not many "died" electrically..

I also had a very tough time extracting the original glow plugs,one is still refusing to come out so I've just left it ,rather than break it off...
I also had one shatter while the engine was running,thought it spun a bearing it sounded so horrible..I'm sure that did that cylinder no justice..eventually I guess it broke up into small enough chunks to blow out the exhaust..

I have had 3 starters in it so far,two of the non gear reduction type,the current one is a gear reduction from a later 6.5..
Knowing these engines are noted for breaking off starter bolts and the engine block,I made sure to put the front brace on the starter,and always fear I'll find the outer bolt hole cracked someday..

For what is involved in swapping a diesel or LS engine into a square body,I dont think its a worthwhile venture really--though a 6.2 does "bolt up" with no real mods,there are about 30 other changes that you need to do to complete the conversion,as noted already--the fuel tank,sending unit,hydroboost brakes,and you will need a vacuum pump if you have a TH350 or TH400,plus change the govenor,torque converter,etc...granted if you have a donor truck its not that hard,but if you do not,hunting all these parts down can be difficult and costly..
You'd be better off buying a factory equipped diesel truck and put that on the road...

I rarely see any 6.2's here in salvage yards,the few you do find are usually junk,blown up,busted crank,seized,etc..if you do find a running one they want 500+ bucks in most cases...the ones sold at local government auctions might be "brand new" rebuilts in the miltary crates,or it might be one that was in Iraq full of sand and overheated,that was taken out,and washed off and put back in the crate....a big gamble,sometimes you luck out,other times you'll get boned..

Personally,if I wanted a truck with an LS gas engine,or a diesel, I'd just buy one that came factory with one and drive it...

I'm getting too old and physically unable to spend hours bending over under a hood,or lying under a truck any more,to undertake an engine or tranny swap...and its probable that 90% of the "backyard swaps" are at least somewhat "hack" and will never rival the factory's build and engineering..and I'm a guy who loved to rip out straight sixes and small blocks and stuff big blocks in everything too...

If I buy another old square body its unlikely I'd go for one thats a diesel..diesel fuel has been an average of 50+ cents a gallon more than gasoline here for decades--only in the past 6 months has it dropped to "only" 25 cents more..for what I do,mostly putting around town,plowing,going to the dump,and a rare "long trip" of 100 miles or so,I would just assume go back to gasoline...but for what I have put the 6.2 in my pickup through I cant bitch,its been pretty dam reliable..but I still never fully "trust" it...sounds like its going to come apart ,but hasn't so far..

That is probably the longest "short" answer that I've encountered yet. :eek1:
 

Latest Posts

Top Bottom