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6.5 Non-Turbo Diesel

i doubt it weighs much more than an SBC - but in my head i was comparing it to the medium duty diesels that are available in light trucks these days. thus, it's your lightest diesel option...
 
A new 6.5 long block weighs 887lbs, SBC cast iron headed long block ~ 545lbs, 7.4 cast iron headed long block ~ 685lbs.
 
Interesting information in this thread. Here are my comments regarding a few of the replies:

1. Light weight - yes, it's extremely light weight compared to most the diesel engines in pickups (Powerstroke, Duramax, Cummins).

2. The above comment about a 6.5 longblock weighing 200+ lbs. more than an iron head BB seems interesting, and assuming a 6.2 and 6.5 are very similiar in weight this is not what I have heard in the past??

3. "My uncle's neighor's 2nd cousin doesn't like GM diesels".......nuff said:rolleyes:

4. I've been seriously wheeling my '90 6.2 Blazer for going on 10 years now. No, I don't consider spinning doughnuts in a cornfield, blasting through a mud puddle on a back road, or jumping parking blocks serious wheeling...but going to places like Harlan, Slade/Natural Bridgle, and other locations where 40" tires and lockers won't get you everyplace and broken D60 shafts occur. Overall I've been really happy with my mostly stock 6.2 even with mediocre gearing (700r4, NP241, 4.10's with 40" tires). There are a few times where I get jealous of the guys running the 300+hp small blocks and 500+ ft-lb. big blocks when a lot of wheelspeed is needed, but other than that it has been great. Super reliable and never left me stranded. The most extensive repairs I've ever performed on the trail was a 5 minute rubber fuel line repair that had a hole rubbed through it, and replacing a thrown p/s belt.
 
So would neither the 6.2 or 6.5 be a good choice for a 78 K30 3+3? I am starting to think I want to remove the 6-8 mpg 454 and go diesel for the 20 +/- mpg economy. But from what I am reading here these motors are only comparable to a stock 350 SB, how is that going to translate to this big of a truck pulling a 24' fifth wheel up a 6% grade? Is it reasonable to get a 6.5 up to 300 hp and be on par with a duramax? Those seem to pull trailers just fine! The 454 is stock and it does a good job of pulling and it is probly only 230 hp.

It has 35's and 4.10 gears with th400 trans.
 
I ended up going with a Cummins 6B. The 454 is a great choice if you have deep pockets to fill the tank. The 6B will average in the 20's with correct gearing and will blow the doors off the 454 with very little modification. I think the 6.2 or 6.5 is a good motor for say a wrangler. You could probably get away with it in a a blazer. K30 3+3...thats a different story.
 
irspiff said:
So would neither the 6.2 or 6.5 be a good choice for a 78 K30 3+3? I am starting to think I want to remove the 6-8 mpg 454 and go diesel for the 20 +/- mpg economy. But from what I am reading here these motors are only comparable to a stock 350 SB, how is that going to translate to this big of a truck pulling a 24' fifth wheel up a 6% grade? Is it reasonable to get a 6.5 up to 300 hp and be on par with a duramax? Those seem to pull trailers just fine! The 454 is stock and it does a good job of pulling and it is probly only 230 hp.

It has 35's and 4.10 gears with th400 trans.
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Again you will hear that from a lot of people, but I have friends with 6.2 stock in their 3+3 and they tow big race car enclosed trailers, they are happy with it, they are thinking about adding a turbo to be able to race with the duramax guys while towing (things get a little slow when towing 45-50 mph) but it does the job.
I had a 350 in my 3+3 and it did fine for towing so it depends on what you expect from your truck.
I didn't expect it to race down the highway with a 24' trailer behind it, and here in CA anyway you can't go past 55mph in tow legally :D
 
You don't often come across an engine that both has great mileage and towing power. You have to trade one off for the other.

While a diesel engine is closer to having both (I get 17 mpg with a 360 horse / 650 ft lbs duramax), you can't expect to trade a 8 mpg 454 out with a 20 mpg 6.2L diesel and expect to have the same towing abilities as you had before.

I personally love the 6.2L diesel engines, and have never had a problem with one (cept for one that burned up half the bearings after an oil passage plugged up with something, but that'd kill anything) and swapped one into my K25 with a turbocharger from a 6.5L and an NV4500. The engine in my K25 far outperforms the old 350, and would probably take a similar era 454 on a very good run for it's money both with towing and acceleration.
 
The old GM inline 6 would get the job done, just a matter of what your expectations are. If you are used to the 454 the 6.2 or 6.5 will be disappointing until you stop at the fueling station. Neither 6.2 or 6.5 can compete with the duramax, powerstroke, cummins, they are a different class of motor so there is no sense in comparing them. The 6.2 or 6.5 can pull that trailer down the road but it's gonna work like hell at it to break 50mph.

Geared correctly a "real" diesel will definitely make close to the 20's and have all of the power and then some of your 454.
 
I've mentioned this comparison several times before, but years ago when the 6.5 turbo first came out my cousin traded his 2 year old 454 TBI truck in for a 6.5 turbo version. He pulled a big goosneck trailer ("dual tandem" version = 2 axles, 8 tires) with a backhoe for his regular job almost daily, and hauled grain wagons on the farm in between. His comment was that the 6.5 turbo pulled just as good as the 454 TBI, but got twice the fuel mileage.

I've owned a 6.2 powered K5 since '94 and daily drove it for years, and even with good gearing (4.10's and 33's) I felt it was kinda' doggy on the road even empty. Didn't tow much but did haul a 3,000 lb. boat and about an 8,000 lb. trailer short distances a few times and to be perfectly honest I think it would be struggling to maintain highway speeds on anything but perfectly flat roads. For comparison my current daily driver and tow rig (pulls the K5 now) has a 300 hp/360 ft-lb V-8 in it and has seriously more seat-of-the-pants power in all conditions than the 6.2 and it works hard pulling a 9k trailer up a long grade.
 
A small block making good horse power and torque numbers will never tow as good as a big block or diesel making similar numbers. The reason for this is the fact that the small block makes it's power much higher in the RPM range and will have to wind = work harder to make the same numbers. A big block makes more power on the low end due to the sheer mass of it's rotating assembly...simple physics. This is good for towing but hard on fuel economy because more mass and larger volume require more fuel. The advantage of the diesel is it makes it's power nearly off idle. In turn it does not have to wind to make power, therefore reducing fuel consumption. This incurs other things as well like longer life. A diesel will always have greater fuel economy than a gasoline engine simply because diesel fuel contains more energy per unit than gasoline. All of this also allows use of less cubic inches to make comparable power. All said, the diesel is a no brainier for towing due to less work and more efficiency. Trains and rigs all run diesels enough said. Without a turbo you will have a dog loaded or unloaded because diesels due not utilize spark advance. Better diesels will make more power with very comparable fuel consumption to the 6.5 or 6.2 because they are more efficient, utilize better internal geometry, better turbos, better fuel injection, and most importantly better engineering which allow things like much higher compression ratios. 6.2 and 6.5 = proven reliability and fuel economy but the lack of internal strength to make traditional "diesel" power.


6.2Blazer said:
I've mentioned this comparison several times before, but years ago when the 6.5 turbo first came out my cousin traded his 2 year old 454 TBI truck in for a 6.5 turbo version. He pulled a big goosneck trailer ("dual tandem" version = 2 axles, 8 tires) with a backhoe for his regular job almost daily, and hauled grain wagons on the farm in between. His comment was that the 6.5 turbo pulled just as good as the 454 TBI, but got twice the fuel mileage.

I've owned a 6.2 powered K5 since '94 and daily drove it for years, and even with good gearing (4.10's and 33's) I felt it was kinda' doggy on the road even empty. Didn't tow much but did haul a 3,000 lb. boat and about an 8,000 lb. trailer short distances a few times and to be perfectly honest I think it would be struggling to maintain highway speeds on anything but perfectly flat roads. For comparison my current daily driver and tow rig (pulls the K5 now) has a 300 hp/360 ft-lb V-8 in it and has seriously more seat-of-the-pants power in all conditions than the 6.2 and it works hard pulling a 9k trailer up a long grade.
Click to expand...
 
Ive got a 1994 6.5 in place of a 6.2 in my '84 cc 4x4. It has a banks sidewinder turbo/exhaust kit meant for a 6.2. IT has 4.10's 35's, and an NV4500 5 speed behind. it.

I tow my wheeler with it.

It is a mechanical fuel injection, without the turbo I couldnt imagine what a dog it would be. You cant compare it to a cummins, but for what it is it does great, and my rig weighs in at 7500lbs.

Also, I get 16-20mpg out of it.
 
Thanks for all the replys, it all helps out. Have any of you seen this thedieselpage.com/finale.htm. They say the 6.5 can be comparable to the cummins and powerstroke and put out 300 hp. Not sure how much all those mods costs to get it to that level. I am not looking for a race truck. Just wanting comperable or better towing power with most importantly good fuel economy. So I could either go through my 454 and build it up to 400-500 hp and maybe only ever get about 10 mpg or put in a built 6.5 with 300 hp for the same money (?) and get upwards of 20 mpg.
 
don't forget to consider the cost of the swap in this. you're going to have some decent money put into the swap that will take a decent amount of time to make up for in the fuel economy gain.
 
irspiff said:
Thanks for all the replys, it all helps out. Have any of you seen this thedieselpage.com/finale.htm. They say the 6.5 can be comparable to the cummins and powerstroke and put out 300 hp. Not sure how much all those mods costs to get it to that level. I am not looking for a race truck. Just wanting comperable or better towing power with most importantly good fuel economy. So I could either go through my 454 and build it up to 400-500 hp and maybe only ever get about 10 mpg or put in a built 6.5 with 300 hp for the same money (?) and get upwards of 20 mpg.
Click to expand...

You are missing the point.
The more power you squeeze out of the same engine, the less mileage you can get.
There is no way you will get 400-500 HP out of a big block and get 10mpg.
And in the same reasonning when you get to the 300hp 6.2-6.5 diesel, no way can you still get 20 mpg.
The only way you can compare is for the same power, the diesel will have more mileage, how much more will depend on your driving style.
 
Ditto

To get 300hp out of a 6.5 you will have to dump fuel down it's throat. You will not touch the 20's.

Duramax, Pstroke, and cummins are all capable of well over 300hp with little work. You will pay far more money to get that power out of a 6.5.

A 12V cummins is easiest to make power out of because it is non-electronic. They are also very efficient and have proven 400,000mi + life spans.

I have a friend with a 12V cummins, 1 case of beer, 2hrs, tweak of pump and it's about 300hp and 550ft/lb trq. It's running about 16mpg in OD with 33's and 3.73's on the highway.
 
I think he's geared just outside optimal that and he drives it if you know what I mean.
 
I would really like to know if any of you read the article on this page thedieselpage.com/finale.htm.

They claim they got 10.8 loaded and 17-20 unloaded mpg out of a 6.5 that they modded producing around 300 hp. Of course to find out how will only cost you $24.95... Which would be fine if it were true. But from your guys real world experience your saying its not really feasable. Or did they really prove a 6.5 could be competitive with a Pstroke, cummins and Dmax like they claim?

I know 10 mpg out of a 500 hp 454 is not really to be expected. I just put holley projection on the truck hoping to get a gain in mpg and I am not sure if I have or not yet. Its a weekend warrior so I dont drive it much and have not had a chance to track the mileage. Basically my point was I figure if I am only getting about 6 mpg with it now, by pumping up the hp at least I would be getting real power out of my 6 mpg. Then I could blow up the hills at 85 mph half throttle instead of 35 mph wide open throttle. Cause thats important! :D
 
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