6.2 vs 454

[Detroit Dan]

been thinking about finding a cucv donor for some time. I wanted to take the 4.56 srw axles and put them under my fleetside dually. I love the 'tucked' dually look, but the limitations on tire sizes drives me nuts. Right now I've got 235/85s and a 6 inch lift, which looks great out back but the front tires look weenie. I'd like to swap in the srw axles just to run some 35-37" rubber.

Meanwhile, the carbed 454 is absolutely brutal on fuel. And I miss my 6.5td truck, so I'm thinking about dumping the 454 in favor of a GM diesel. The donor truck could give me pretty much everything I need, but I know I would want to add a turbo and turn up the fuel a tad. I know 4.56s behind the 454 would turn 37s, but the 6.2 with 4.56s came with 235./85s, hows it going to like tall tires? Think I'd be able to tow anything with it? 35s would probably be all I can fit legally, but 37s would be nice because the military ones are cheap and have tough sidewalls, which should be better for towing.

Am I being stupid? As it stands the truck is only used for dump runs and towing the camper a few times in the summer. If I could get a little more than zero miles per gallon with it I'd drive it every day. It would be nice not to have to have two vehicles, one for daily driver and one for chores.

 

[Koots]

I found going from worn out 31s to 35" KM2s wasnt nearly as bad as i expected, especially with 3.42 gears. Im sure id see some issues when towing, right when i need that torque multiplication. The 4.56s and 35s should be about perfect for each other. Right at the balance of torque multiplication and economy for a DD/occasional hauler.

 

[Detroit Dan]

35s would probably be a wiser choice, since civilian flotation sizes rarely measure what they say on the sidewall, and I'd be more likely to be close to legal. Recently was checking the law and it says 30 inches to the bumper, which was the old way, I thought they changed to measuring to the frame at some point. I've been measuring to the frame for years. But state inspection says to the bottom of the frame.. Which is 2-3 inches higher than the bumper. Long as I can get it stickered (which I can), getting pulled over shouldn't be a problem with 35s. 37s I can see attracting a lot of unwanted attention. Especially since I'd need to add a 3 inch bodylift, which wouldn't add any frame or bumper height, but would make the truck look even more massive going down the road.

 

[Koots]

My K5 w/700R4/3.42s and 35s got a measured 16MPG (US gallons, i never use the metric gallons)

Which is what my parents 09 Sierra gets according to the DIC. This is an ECSB with aluminum 5.3L w/AFM so i was expecting better.

 

[Detroit Dan]

I've heard numerous claims of 6.2s getting 20+ mpg. I'm thinking about buying something like what you have to start, adding a 6.5 GMx turbo, and then if I'm happy with it, finding that cucv donoer and re-doing the 1 ton. But, idk, I really need to be able to pull 10k, and I don't know if a 6.2 has the nut. My 6.5 td when it was stock could barely move it in the mountains.
I've driven Blazer cucvs a lot, and always felt that they go pretty darn good for only having 3.08 gears. But that's a long way from moving a big crewcab with 4.10s or 4.56s.

I know that the 6.2 isn't a rocket, but I've become accustomed to the power and acceleration of my 454. I'd like the sound of a diesel (and a little black smoke) coming out of stacks, and to not have Dmax guys laugh at me.

Just wondering at this point if it's all worthwhile.

 

[deejaaa]

here's an excerpt from the diesel page:
"A typical 6.5TD with 3.42 gearing will produce in excess of 20 mpg at 65 mph because the engine rpm at that speed is right at the engine's torque peak of about 1800 rpm. A truck with 4.10 gearing is running at about 2250 rpm at the same speed, which typically produces about 15 mpg. A 500 rpm difference might not sound like much, but in a diesel, that's about half of the useable rpm range.

6.5TD engine rpm (4L80E automatic transmission) and typical fuel economy at 65 mph:

3.42 gearing 1880 rpm (21 mpg)
3.73 gearing 2050 rpm (17 mpg)
4.10 gearing 2250 rpm (15 mpg)

For high speeds, the GM diesel will deliver the performance as long as you gear your truck for the speed you want to drive. The a 3.42 gear ratio will allow you to drive at any sane speed. The 3.73 and 4.10 gears are more at home towing at a lower speed.

Recommendations for towing with the 6.5TD:

Up to 4,000 lb trailers: 3.42
4,000 to 6,000 lb trailers: 3.73
6,000 to 8,000 lb trailers: 4.10

These are based on reports from 6.5TD owners who. Non-turbo GM diesels should use the next lower (higher numerically) axle ratio increment to ensure adequate towing power. Wind drag factors needs to be considered as well.

For towing trailers that weigh 4,000 pounds or less, a 3.42 differential ratio is probably the best choice in a 6.5TD equipped truck. Your truck will tow heavier trailers up to the maximum trailer weight of 8,000 lbs better with a 3.73 or 4.10 ratio, but your fuel mileage and comfortable cruise speed could suffer when not towing. A 4.10 gear ratio is more useful when used to tow trailers heavier than about 6,000 lbs."

 

[Missy Good Wench]

The 6.2's (if in good order) could easily see 20+ MPG even in a 2500 Burb 4x4

As far as going to the trouble of swapping an engine inot a rig that is used for minimal service, ???? not sure on that one.

A 454 with a well set up Quadrajet should get fair MPG unless being romped around hard.

The 6.2 is going to seem pretty anemic in comparison.

Just an aside here.

Back many years (late 80's) we owned an 86 Burb 2500 4x4 with stock tires and 4.10 gears.

On the highway it would routinely drag down 22 MPG at 60 MPH.

we drove it from home here in Newberg Oregon to the LA area a couple times and to Northern Idiaho a couple times and pushed it hard.

The LA trip saw 22 going down and 20 coming back.

The rig served us well for over 250K miles. We bought it with 60K on it.

So it had 310K on it when we sold it. That was in 1994, and I still see it out on the road around here from time to time.

The 6.2 is certainly not a bad engine.

Power is marginal in a large rig. The J code engnes were rated at 160 SAE so they are no ball of fire.

A 1 ton is gonna be a tad bit of a slug as compared to the 454.


have fun

Missy

 

[Detroit Dan]

well it would eventually see a turbo, but I doubt it would ever get to the point where it is as fun to drive as the 454. Very good point about the limited usage. I like to think I'd drive it more if I could afford it, but it's true, it's a big job and expenditure to build a truck that I currently only use for dump runs and camping trips.
As much as I love the truck, I'm afraid eventually I'll end up unloading it and buying a 2500hd. It would be quite nice to have a truck that will pull a big trailer, carry the family, and still be able to drive it everyday. Been seeing early 2000s HDs for well under $10k. Always said I'd never buy a 6.0 because they suck on gas, but in reality they get a lot more than my 82 gets. My best was 9mpg, but beating around town I'm likely only getting 6-7. Guy I bought it from said he got 10 with it, but I can't, not with my right foot. The carb is rebuilt, and she's all tuned up. Keep in mind, I've got a 3 speed trans in front of 4.10 gears. I've looked into overdrives but again, the gain won't pay for the investment.
I bought this Blazer as a daily driver to save fuel. It seems far better than the 1 ton, but I'm already getting tired of it. Rides like a hobby horse with that short wheelbase.

 

[WarWagon]

Far easier to get a truck with a 6.2 already in it. Cheaper with a pre-blown engine. The 6.5/6.2 trucks are cheap vs. other brands. Really, it costs money to swap diesel for gas with all the little parts. Then the 6.2 is more expensive to run parts and maintenance wise than a gasser.

The 454 will get a hard run for it's money from the 6.2 if you skip the boat anchor GMx turbo and put a 'real' turbo on it. (Like the ATT) I am not easy on the 1995 3/4 ton burb and am getting 15 in town. It does better MPG than the 2005 Duramax. The NA 6.2 would do better but, it really can't get out of it's own way and not something you want to get after a 454. I would get 10-15 with a 350 Yukon and a smaller parts bill.

How many miles do you run a year? After all at 6MPG you can still buy a lot of gas vs. the expense of swapping an engine and getting a good turbo. An OD transmission will help your MPG on the 454 by slowing it's RPM down.

 

[Detroit Dan]

I know, I dont even drive it much, because of the mileage. I always keep another vehicle around as a DD. I like to think I'd drive it more if it was more efficient, but maybe not. It's never ever going to be very efficient. I agonized over OD for a long time, but I dont really think it would be worth much, unless I was driving it more. RPMs arent even the problem, because I rarely take it on the highway, it hardly sees more than 45. Problem is it's a gigantic motor with a big carburetor on it. Even the later TBI and vortec 454s, with computers, fuel injection and overdrives still sucked on gas.
If it wasn't for the rareness of the crewcab, I would have turned to something else a long time ago. I change my mind a lot. I'm also never happy with anything. I kind of thought the 6.2 swap would be simpler, coming from essentially the same trucks. I would have them parked side-by--side to make it easier swapping everything in. But, in the end it would be a huge project and I dont have that much time and not much money. And Im kind of limited to engine in the old trucks. 454 easily does what I want, 350 would not, not without beating it's brains out anyway. Maybe building a stroker could get the torque up there, but I dont want to do that. Only thing left is 6.2, with a turbo added on. Screw it, I'd spend thousands, which I may as well just dump down the bottomless gas-filler neck.
I think for now I'll keep the crewcab on the back burner. Still trying to decide whether to put the plow on the Blazer, or sell it and buy something different. It's January and I still don't have a plow truck ready. Lucky we havent had any real snow, but I'm also glad I didn't go nuts investing a lot of money into building a plowtruck that would have earned nothing.

 

[figment]

here's an excerpt from the diesel page:
"A typical 6.5TD with 3.42 gearing will produce in excess of 20 mpg at 65 mph because the engine rpm at that speed is right at the engine's torque peak of about 1800 rpm. A truck with 4.10 gearing is running at about 2250 rpm at the same speed, which typically produces about 15 mpg. A 500 rpm difference might not sound like much, but in a diesel, that's about half of the useable rpm range.

6.5TD engine rpm (4L80E automatic transmission) and typical fuel economy at 65

3.42 gearing 1880 rpm (21 mpg)
3.73 gearing 2050 rpm (17 mpg)
4.10 gearing 2250 rpm (15 mpg)

For high speeds, the GM diesel will deliver the performance as long as you gear your truck for the speed you want to drive. The a 3.42 gear ratio will allow you to drive at any sane speed. The 3.73 and 4.10 gears are more at home towing at a lower speed.

Recommendations for towing with the 6.5TD:

Up to 4,000 lb trailers: 3.42
4,000 to 6,000 lb trailers: 3.73
6,000 to 8,000 lb trailers: 4.10

These are based on reports from 6.5TD owners who. Non-turbo GM diesels should use the next lower (higher numerically) axle ratio increment to ensure adequate towing power. Wind drag factors needs to be considered as well.

For towing trailers that weigh 4,000 pounds or less, a 3.42 differential ratio is probably the best choice in a 6.5TD equipped truck. Your truck will tow heavier trailers up to the maximum trailer weight of 8,000 lbs better with a 3.73 or 4.10 ratio, but your fuel mileage and comfortable cruise speed could suffer when not towing. A 4.10 gear ratio is more useful when used to tow trailers heavier than about 6,000 lbs."

That's not factoring in the change in tire size. Match the drop in gear ratio with a taller tire size and still can run optimum RPM's for fuel milage. He should go to a 4-53T,or 4-71 and get the same power as the 454 and still get 30 mpg

 

[L98TPI]

Meanwhile, the carbed 454 is absolutely brutal on fuel. And I miss my 6.5td truck, so I'm thinking about dumping the 454 in favor of a GM diesel.

How about instead of going with the axles or a 6.5 transplant, provided the dually body chassis is in good shape, go with a Duramax swap. Find a rolled one and swap in the engine trans transfer case, axles maybe, and so on. Not a huge amount of work beyond converting to a 6.5, but more worth the effort. An 82 4x4 crew with a Dmax has huge cool factor, and a excellent truck when done. I for one would be drooling :hihi:

 

[Detroit Dan]

That's not factoring in the change in tire size. Match the drop in gear ratio with a taller tire size and still can run optimum RPM's for fuel milage. He should go to a 4-53T,or 4-71 and get the same power as the 454 and still get 30 mpg

Now you're talking! I would love the sound of a 2 stroke Detroit Diesel!. Heck I might even break my own rule and put stacks on it so I can listen to it. That's where I got my nickname from, I used to drive a 6-71, the guys in the shop always heard me coming and going.

If I win the lottery I'll have the truck completely restored and put a D-max in it, but for now that's way out of reach. Where I work deals with insurance salvage, and wrecked, junked burnt blown up Duramaxes that have been under water still pull down 8 grand easy. Not to mention replacing injectors would cost more than I have in my whole truck.

 

[Koots]

6V53 swap!

 

[figment]

6V53 swap!

No that's getting too heavy.

I found a vid on you tube, the guy put a 4-53t in a '03 3/4 ton with the allison tranny. I think Phoenix casting and machining Inc. mite be a place to check out. Those little 4 bangers put out the power and some have jakes on them and are still lite enough to not overtax the suspension.

I've thought a lot about putting one of those in my '51, except no stacks. 5" side pipes and weld some expanded metal on them and paint them flat black and set them out far enough to use as step. I would face them down as to not deafen the Trooper next to me.

 

[Koots]

My old coworker said told me that if i ever wanted to swap in a 2 stroke destroit into a truck, let him know and he would set it up right for me. He has done extensive work on them in his many years and he told me any one of them would make a damn fine engine.

A 4-53T still does sound like a pure beast! I know of one just sitting in this logging truck too...wish i knew who the owner was LOL

 

[red]

I know the feeling Detroit Dan, I've got the same issues just the older body style, manual trans and a built up 454. Wonderful power, but horrid fuel economy which sucks since I drive mostly highway with the truck.

Cheapest and easiest diesel swap to make the goals would be either a turbo 6.2 or 6.5, question is which to go with? I've heard the 6.2 has a slightly stronger block because of the less amount of metal that's been bored, but slightly less power because of it. Maybe a 6.2 with a good turbo, exhaust, marine injectors, and an intercooler might meet the bill?

 

[WarWagon]

There is no real difference between a turbo 6.2 and 6.5. I am cracking the mains out of a 1986 6.2 turbocharged now and have blown up 6.5's. Exhaust valves and precups are the biggest difference along with injector angle. Use 6.5 heads and there is no 'real' difference. Advantage 6.2 heads with turbo precups for larger exhaust valves. Actually the 6.2's are cheaper by half to buy used as everyone wants a 6.5.

Only the latest Optimizer non-GM built blocks handle the cracking issues period. Everything else GM is a matter of time before cracks doom it.

Skip the intercooler and marine injectors. ARP heads studs would be money better spent.

 

[jmack91z28]

I'm in the same boat you are. My 454 gets about 7-8 mpg, and I only fire it up once every two weeks to make a dump run or tow something big. I've been tossing around a 4bt swap for it. But it would cost me probably $6-7000 all said and done the way i'd like it. I just can't justify that. I've even tossed around buying an 04.5-06 duramax with 150k miles or so. But then after monthly payments it would cost me more too.

I'm also like you, I don't think I can get rid of the power and sound of a big block. Everytime I fire it up I quickly forget why I wanted to sell it in the first place. I'm just gonna suck it up and keep using it.

 

[DEERE3594]

Go with a 7.4 OR 8.1... so much cheeper to work on.. witch equals more money for fuel