Cummins in a K5

[Smithy316]

Full disclosure: I'm probably just a stupid kid (16), so feel free to be harsh
I've been looking at K5 blazers for my first car. I would probably be able to afford a decent one next summer. The biggest problem is the mileage. I know no one buys a truck for the mpgs, but I still don't want to be getting 5 mpg highway. So I started looking into the 6.2 diesel that came in 80s Chevys. Some people love them, some hate them, but I'd consider getting one. Obviously a Cummins would be better, so my question is would it be cost effective(<$4000?) to buy a roller/bad engine K5(I know someone who is selling one for $600) and then buying a Cummins/donor truck(probably 6BT because 4BT seem to be difficult to find) to put in it($2-3k?). Would this project be too much to tackle at my age? I have limited experience with cars, none with diesel. My dad could help me and he tests Corvette engines for a living, but again he has extremely limited experience with diesels, however, he has friends with diesel experience who may help. Of course, I don't have the money now so I have plenty of time to think about it and also this year I'm going to take a mechanics class at school; maybe that'll help give me an idea of what I'm looking at. Also, if the cummins plan fell through somehow, my dad has an 84 C20 that's rusted out, but it's mechanically sound, so that engine could easily be swapped into the blazer, so it wouldn't be a complete loss. So Cummins+roller or just settle for the 6.2 and don't give myself extra headaches?
(Also what kind of MPG would I be looking at in a K5 with a Cummins?)

 

[rompinstompinmudmonkey]

I swapped a Cummins into my V30 and it gets about 17-19 mpg.

However, this is not a cheap swap nor is it for a novice. I would guess the average Cummins swap would be 5k+, depending on how much you can score the parts for

For someone your age I would recommend buying a 6.2 truck and learning the mechanical fundamentals of the truck before tackling a very involved swap

 

[Smithy316]

I swapped a Cummins into my V30 and it gets about 17-19 mpg.

However, this is not a cheap swap nor is it for a novice. I would guess the average Cummins swap would be 5k+, depending on how much you can score the parts for

For someone your age I would recommend buying a 6.2 truck and learning the mechanical fundamentals of the truck before tackling a very involved swap

Where does all the cost come in?

 

[rompinstompinmudmonkey]

Your biggest investment will be the engine

And you'll need to buy or fab a new cross member to fit the engine

The oil pan will hit the axle if the truck isn't lifted, so plan on a 4" lift and the steering corrections too

6 lug axles will live for awhile under the truck, but the front will eat ball joints because of the weight.

With the right adapter a GM trans will bolt to the engine, but a stock auto trans won't live very long so you'll need to either build a trans to hold the power or swap to a heavier trans all together

Depending on where you live it may not even be a legal swap. If you have annual inspections or have to pass emissions it probably won't even make it past the referee station

 

[Smithy316]

Your biggest investment will be the engine

And you'll need to buy or fab a new cross member to fit the engine

The oil pan will hit the axle if the truck isn't lifted, so plan on a 4" lift and the steering corrections too

6 lug axles will live for awhile under the truck, but the front will eat ball joints because of the weight.

With the right adapter a GM trans will bolt to the engine, but a stock auto trans won't live very long so you'll need to either build a trans to hold the power or swap to a heavier trans all together

Depending on where you live it may not even be a legal swap. If you have annual inspections or have to pass emissions it probably won't even make it past the referee station

Thanks for all the info. I guess I didn't really realize the magnitude of the project(just my ignorance). I'll look into the 6.2 and maybe a turbo for a bit more power

 

[Richcz28]

I wish I had my 6.2 when I was 16. If you find one with a 4 speed, put some glass packs on it and you will have a blast. They are loud mean sounding engines. You will get decent mileage if you want to and with the right gears and tires. I got 21 on the highway before I lifted mine.

Your new blazer will have plenty of projects without worrying about an engine swap. I also wouldn't be worrying too much about the turbo swap.

All from hearsay, you can think long term about a 4bt. I've heard they can deliver exceptional mileage with plenty of power.

 

[jekquistk5]

I agree with what everyone said. Here is how it goes..

post up pics on here of k5 you are interested in
We will help decided how much work is involved
Buy K5
Lift K5 and new tires
Upgrade axles
upgrade to bigger tires
Upgrade engine, trans, doublers etc
rinse lather and repeat!


Welcome to the brotherhood!

Also spending 25 bucks a year for a membership is one of the best things you can do

 

[paratrooper307]

Some good advice here. For your first car, you'll really want something that's operational and you can build as you go, starting with the little projects and moving to more advanced modifications as your aptitude and interests grow. I don't know what your financial situation is, but when I was sixteen money was a factor, so tackling major builds wasn't an option.

A Cummins swap is definitely not for the faint of heart. It is expensive, and some fabrication skill, time, and patience are required. It's almost mandatory to have a Dodge donor truck handy, otherwise you get nickel-and-dimed on all the little parts that you need. Keeping another non-functioning truck around may not be in the cards depending on your living situation. Swapping a Cummins in is a great project, but don't expect it to pay for itself unless you do a ton of driving, and unless your goal is bragging rights or towing power (towing's not the best idea on a Blazer anyway) you'll probably be plenty happy with a 6.2, SBC, or BBC, and still be thousands ahead. 5K for a Cummins swap buys a whole lot of gas. Despite some of the horror stories you hear, it is possible to build a good truck with okay mileage (for a truck). I see about 10-12 in the city, 15 or more on the highway on a mildly modified SBC with a lift and bigger tires. Not diesel-caliber mileage, but manageable.

 

[shady]

find a good running 6.2 blazer to buy and drive the &@#$ out of it No messing around

 

[Detri Mental]

First time I get on here in like forever, and here this post is.

I put a 4bt in my K5 like four or so years ago.

I get an average of 26MPG mixed driving on 35" Goodyears.

Its loud and vibrates. Doesn't really bother me, my wife tolerates it out of love for me. Fortunately for her it's not my daily driver.

It has been dead reliable.

It cost me close to seven thousand to complete the conversion since I bought a NV4500 transmission outright to go in it.

luckily I have a tig welder, lathe, big pile of steel stock and all other sorts of metal working devices. It ain't something I would want to attempt with a socket set and a hack saw.

Honestly I love the thing to death, and have been completely satisfied with it, but I did it as an aside and didn't need it for real transportation purposes. In your situation, honestly I would recommend just slapping a sbc or something easy in that roller for now until you can get ALL the parts sourced that you will need, and all of the miscellaneous brackets, and doo-dads.
It will take a while to get to that point.

Good luck man

 

[campfire]

The biggest problem is the mileage. I know no one buys a truck for the mpgs, but I still don't want to be getting 5 mpg highway. So I started looking into the 6.2 diesel that came in 80s Chevys. Some people love them, some hate them, but I'd consider getting one. Obviously a Cummins would be better, so my question is would it be cost effective(<$4000?) to buy a roller/bad engine K5(I know someone who is selling one for $600) and then buying a Cummins/donor truck

...

(Also what kind of MPG would I be looking at in a K5 with a Cummins?)

Sorry I didn't get on this earlier. If mileage alone is your biggest problem, switching to a Cummins is less helpful than other (smaller) things you can do to the truck. The guys that I personally know that have done 6BT swaps have either built off-roading trucks or cranked up the engine and fallen in love with the power it can generate. Either way, their mileage isn't what they would have had if they had built for mileage from the get-go.

Because of this, I've yet to meet a 6BT swap that beats my stock 6.2 700R4 LWB truck for mileage. Aside from the automatic tranny, I happen to have a fairly good configuration mileage-wise (anemic gearing, small tires, and stock (short) height. So my truck isn't great offroad. If you're willing to put up with these drawbacks, mileage is great for the class. I had 23-24MPG @ 55MPH, 22 @ 65MPH, and 19-21 MPG in town before I swapped out my intake (slightly higher now). It could still be raised a bit, but this is what came with the truck, ready to run and free of charge.

It does depends on what you're willing to live with, though. You'll never get Cummins power out of a 6.2, no matter what you do with it. And stock 6.2 trucks require patience on the road. They're just slower than newer vehicles (although they keep up fairly well with same-era small-blocks). If you're not willing to live with a slow truck, a turbo is a simple enough project and relieves the characteristic lag that 6.2 engines are so well known for (still won't be a powerhouse). It's simple enough to add little things like that (or getting rid of the c-code intake manifold) that will help mileage/power one bit at a time. But it's a lot easier to build for mileage if you start with 20MPG, instead of 13MPG, IMO. And remember that, even without mods, a 6.2 is still a V8. It's not like you're starting with a 4-banger. The torque is awesome!

A 6BT will offer you everything a 6.2 does, and a whole lot more power, except for one thing-you'll never find one that is comparable in cost and comes ready to drive on the road. Fun project, and really few downsides, but a 6.2 will get you the good mileage without the headaches of swapping. Especially if you're not experienced with engines...swapping one would have a steep learning curve if you've not worked on them previously.

If you decide down the road that you want a fun project, your 6.2 truck will come with several Cummins-friendly diesel accessories that will make the swap easier (fuel system, dual batteries, heater relay already installed, etc) that provide a good foundation for the swap. It would be easier to swap a Cummins into a 6.2 truck than a 350 truck. And definitely consider a 4BT at that time if you're still looking for mileage.

 

[campfire]

And welcome to CK5. There are lots of ideas here, for chevy trucks in every configuration I'm aware of (and several I wasn't previously familiar with). I look forward to seeing what you wind up with. You will get much more out of the site if you sign up to see everyone's pictures. The $25 annual fee is paid back the first time the pictures save you from wasting 6 hours doing some maintenance job incorrectly. I so wish I had had CK5 around when I started out with my projects (not much older than you, either-good on ya for starting young ). It would have significantly changed what I ended up doing with my truck(s), and saved me from re-doing several things (which I am now starting to do )

 

[campfire]

I wish I had my 6.2 when I was 16. If you find one with a 4 speed, put some glass packs on it and you will have a blast. They are loud mean sounding engines.

I've never been a glass-pack fan, but I will say this-my suburban came with one (yes, just one!) glass-pack on it, and it sounds pretty neat (although I think it's obnoxiously loud on the one side). Loud, but it makes the straight-piped gasser engines just sound lame. So, if you want a loud engine, the diesel is able to sound both loud and cool at the same time.

Your new blazer will have plenty of projects without worrying about an engine swap. I also wouldn't be worrying too much about the turbo swap.

Truth-the turbo is a fine project once you get familiar with your truck. But 30-year-old trucks come with a bunch of maintenance associated with them. I would recommend spending a couple years getting to know your truck when you buy one, to get a feel for what things break and at what rates. Some failures will be periodic (like brakes and balljoints), others shouldn't be (like rebuilding axles). But if you pick the wrong time to start a project it's really easy to end up with several things broken all at once. And that's no fun. Nothing says fun like watching a broken truck rust away in the driveway...

I also daily drive 2 of my 30-year-old trucks, and that presents its own challenges. You've gotta stay on top of maintenance if you want to drive your truck every day without getting stranded. Old trucks will not forgive negligence like young vehicles will. This is one reason I ended up with a pair of trucks-either one of them could break without notice, and I wanted a backup.

So-old trucks are a heap of fun, as long as you treat them like old trucks. And, over time, you can replace one thing at a time, until eventually you have a mostly new truck!

 

[shady]

slow isn't really a good definition of a 6.2..... it depends on your comparison... my 6.2 burb would get with it pretty good and even squeak tires on shifts (midline shift kit)... it had enough stock power to DESTROY the internals of my 700r4 (twisted off 2 shafts, blew apart the planetary housing, stripped who knows how many teeth off) when I was trying to hot rod it.... plus it'd get to 85 mph pretty easily on the interstate... point is, if your comparing it to a big block or a cummins off the line it'll look like a snail.... but FAR from a slouch. mine had more go than my stock tbi 350 hands down

 

[campfire]

slow isn't really a good definition of a 6.2..... it depends on your comparison... my 6.2 burb would get with it pretty good and even squeak tires on shifts (midline shift kit)... it had enough stock power to DESTROY the internals of my 700r4 (twisted off 2 shafts, blew apart the planetary housing, stripped who knows how many teeth off) when I was trying to hot rod it.... plus it'd get to 85 mph pretty easily on the interstate... point is, if your comparing it to a big block or a cummins off the line it'll look like a snail.... but FAR from a slouch. mine had more go than my stock tbi 350 hands down

In all fairness, I don't consider my stock 6.2 trucks slow either. But I'm running 3.08 gearing with O/D, which puts me a bunch slower than I could be if I built for that (vs. mileage). I should have mentioned that in the first post.

Overall, the truck is a lot of fun to drive. My observation is that at 65MPH (110HP max in 3rd gear with my non-powerful gearing, according to the engine curve), the truck hangs with traffic pretty well, and I do pass folks whenever I need to. Downshifting from OD (4th) is minimal here in the Midwest (I'll downshift on anything greater than a 4% grade, approximately). And it definitely likes to walk away from me speed-wise. It took me quite a while for me to be able to drive it without my speed creeping up whenever I wasn't watching. But in town is where the 6.2 seems to shine brightest. The low-end torque makes a huge difference compared to driving a similarly-powerful 350. I don't have to downshift to get a sudden surge of power. I simply press the pedal. I believe the 6.2's sales pitch was "Big Block Torque with Small Block Economy."

Off the starting line, I feel like my truck would beat a corvette up to about 5MPH or so...

 

[Smithy316]

On the 6.2 discussion, I just came across a 86 GMC 6.2 CCLB DRW for $1200. I'm not sure what condition, what trans, 2wd or 4wd, or pretty much anything else. But how much would the DRW effect mileage? And how easy/hard would it be to make it SRW and would the gain in MPG be worth it?