Diesel Swap: 6BT or 6.2 Donor Truck?

[BorntoVenture]

Diesel Swap: 6BT or 6.5 Donor Truck?

I've been reading and lurking on several of the diesel sites I know of about the possibility of swapping my 7.4L gas guzzler out with a diesel. So far I've found that it's possible to swap a 4BT or 6BT into my Suburban without major problems but it seems to me finding a donor truck with a 6.5L diesel would be a better route to go since that engine was offered in my Suburban.

I wanted to ask this here since I've read that many members of this board have done diesel swaps and hopefully someone has experience with the GM 6.5 engine.

I should note that the main reason for my interest in this swap is for fuel economy. I also have no prior experience with diesel trucks or engines so when I do this swap (next year) it will be a new world to me all at once!

Thanks for any help!


[Edit] - Changed 6.2 to 6.5 which is the correct diesel engine offered. Too much information read today! [/Edit]

 

[wapitichaser]

Personally I would stay away from the 6.2 and the 6.5 chevy diesels. They are not know for their reliability or power. The cost would outway the return on your investment. You would be better off looking for a vehicle that already had a diesel in it. Some states will not allow a diesel to be put in a vehicle that originally had a gas engine. Check your state's regulations. My .02.

 

[olympiccop2002]

My vote goes for the Cummins. They are easy to work on and they are fuel efficient. The older 12v will pretty much work in anything. Make sure you do a thread on the build. Should be a nice rig.

:costumed-smiley-007

 

[ntsqd]

No doubt that the 6BT is superior to the GM 6.X series diesels, but I think that the 6.X series gets a bump rap. Depending on the intended use a late model engine can be a good choice. I wouldn't want one for pulling a 6 horse slant load trailer, but for bumping around in the back country it is my first choice.
Americans tend to get caught up in needing the biggest/best when the second or even fourth choice down from the top of that pile may actually be better suited to the actual use.
Since these engines came in GM trucks and Subs up to roughly the start of the D-Max Engine, swapping one of them in should be entirely factory supported and require very little in the way of custom fabrication. I'd hunt for a wrecked donor though. Trying to buy all of the necessary parts from a dealer will break you pretty quickly.

In a 73-91 Sub the 6BT is tight to the radiator and the firewall, and doesn't leave a lot of room for the intercooler. I don't know about the later models.

I've personally no interest in a 4BT. A 4cylinder, 238 cubic inch (3.9l) diesel engine can't help but rattle and shake excessively at idle.

 

[benjamin]

X2-- Here's a site w/ a couple of diesel subs and info. on what can be done with them.
http://www.oliverdiesel.com/index.shtml
They also show a 6.2/6.5 diesel swap into a D110.


Dennis

 

[alosix]

I think between my lust of a mini diesel in my TJ and a 6bt in my M725 I must have read everything about doing swaps at some point.

For a surburn, I would probably go hunt down a turbo 6.5. It would be the easiest thing to get in there. It should already have a diesel version of a TH400 on there though I think they are suitable for 'normal' GM trannies since they don't quite have the really extra low grunt of a cummins.

The 4bt and 6bt are really nice engines. But have you ever wondered why a 2500 ram, even 2wd sits as high as it does? That hood and suspension height is there to get the 6bt to fit. It is a VERY tall engine, and pretty darn long as well.

The 4bts make a nice swap. They still have that tall problem, but they are shorter, and in a 1/2 ton truck they work well as long as you aren't towing something rather heavy.

I also found that the 4bts were more expensive than 6bts due to demand and availability.

If you don't mind a ford or wiring the later model 6.0s are light, compact, and make good power. Same can be said for the later model duramax though they are expensive to find in the parts yards.


For my M725, we had a whole 6bt donor truck lined up. I was really excited, then the deal fell through. Ended up with a 5.7 hemi, which is still entertaining.

Jason

 

[BorntoVenture]

Americans tend to get caught up in needing the biggest/best when the second or even fourth choice down from the top of that pile may actually be better suited to the actual use.

I like this saying, so true to boot! I've been reading even more and more since getting home from work tonight and it looks like a 4BT is out, the 6BT will be more work than I originally thought with the adapter to my 4L80e pushing the limits of room in my suburban. It's really looking like a same/similar year model donor 6.5 truck will be the best bet for me. It will net me plenty of torque (more than the 454 in it now) with much better mileage. I'm planning on doing this swap this time next year so I have plenty of time to get everything ready.

 

[Bullseye240]

Try here for all the info and support you will need for the 6.3/6.5 engine.
http://www.dieseltowingresource.com/forumdisplay.php?f=93
I love my 94 6.5 Blazer, and yes it's factory installed! 244000 miles and counting.

 

[olympiccop2002]

A friend of mine had a 6.5L Turbo Diesel in his farm truck. It did very well on the mileage (low to mid 20's if I remember right) and was plenty stout. Good luck with your search.

 

[Rot Box]

I have been through EVERY known problem with the 6.5 TD aside from the broken crank syndrome. The problems I had are NOT something that you would ever want to deal with on a vehicle that takes you away from civilization or on any vehicle that you count on. That being said I do disagree that ALL 6.5's are unreliable. There are certain years to avoid. My brother had a 93 with 550K miles on it before a rod let loose :Wow1: Where as mine was on it's last leg at 50K miles... It's very hit or miss depending on model years.

The www.thedieselpage.com offers some manuals and guides that are very helpful in choosing the right 6.5 for your swap--purchase them before you make your decision.

A short run down: 92-93 are great because of the mechanical fuel injection. 94-95 came with the E prom electronic injection and 96-later had a PCM. On electronically controlled trucks the PMD (pump mounted driver) is known to get really hot due to it's location in the engine valley, and when it fails the injector pump no longer supply's fuel. It is a $400 part and unless it's relocated (to a cooler spot outside of the engine compartment) it will likely fail prematurely.

All years before 96.5 had poor cooling flow that was later upgraded to a high flow dual t-stat housing along with a higher gpm water pump in 96.5 and later engines. These engines WILL cook themselves if worked hard unless you have the later model cooling upgrade.

Also 97-98's are known for a very poor block the is known to crack and I would just avoid those years altogether they are probably the worst of the 6.5 models.

Poor harmonic ballancer design will eventually lead to crank falure.

If you don't see a puddle of oil under it--check the dipstick! Very poor hose connections.

Coolant temp over 217 degrees is quick way to crack the heads, and it's very easy to get them hot.

There's a lot more, but nothing else is coming to me right now :coffeedrink:

My truck when running well (which was not often) achieved very good fuel mileage (up to 24mpg) and very good power. I will never own one again--ever. My Cummins gets the same milage with a lot more power, and I'm not under the hood of it every day saying "what now!?!" I don't think the biggest Ford fan in the world could ever say a Cummins is unreliable, and hold a strait face.

If you want more advise on the 6.5's I'm happy to help as have seen it all (no seriously), but if I were you I'd go with a Cummins or even a 6.9/7.3 Ford IDI before I ever considered the 6.5 just my .02. :elkgrin:

GM 6.2/6.5 links

www.kennedydiesel.com
www.heathdiesel.com
www.thedieselpage.com

Cummins Conversion:

http://www.avalancheengineering.com/new_products.html (crossmember adapter)
http://destroked.com/parts.html (GM adapter plates)
http://www.4btswaps.com/forum/index.php (Expo's DIESELCRUISERHEAD's webpage)

 

[spencyg]

I would go with a Cummins hands down, and I think the 4BTA would be an excellent choice. You can reliably get 250hp/450ft-lbs out of it which is more than enough to haul around a 'Burb. Its not too long in the engine bay and is easy to work on. I've known way too many dead 6.5's to ever consider them even a distant contender. Yes, the cummins will be more work to install than a 6.5, but the reward for the hard work will far outweigh the drawbacks. You could bolt many different transmissions to the Cummins as well...overall I'd say its a no-contest.

Spence

 

[highlandercj-7]

There is no other option IMHO. Cummins 6BT is one of the best engines ever built. It will make that sub haul and get great fuel milage. I'd expect you to see 20MPG with the big C. I would love to build a 94 Crew Cab Silverado 4wd with a Cummins and a D60 front.

 

[Rot Box]

I would much rather swap a mechanically injected Cummins than an electronic 6.5 TD... Also with the DI (direct injection) Cummins you could use your current radiator. With the 6.5 IDI (indirect injection) you would need a new--much larger--radiator out of a donor vehicle at best.

With an extra cooler your 4L80E transmission will hold up good to either engine, but it could be expensive making it work with the Cummins Vs. finding a donor harness for the 6.5. Either way you will need a different torque converter.

 

[BorntoVenture]

Thanks for all the great information everyone, this has been very helpful! I was not aware that the 6.5's had such a bad history compared to the Cummins 4BT/6BTs. Needless to say I'm back looking into the 4BT or 6BT again, partly because of the information on the reliability and partly because I found out this morning that the dash harness has to be swapped along with the ECM harness on a 97/98 suburban.

On to do more reading! :Wow1:

 

[rewell6]

As a current owner of 3 6.2 suburban's I would have to consider the cummins. Especially if it is totally mechanical. The 6.2's need power to the pump to keep the fuel solenoid open.

However you can pick up some great deals on 6.2's. Everybody gets them confused with the original gm diesel which really was junk.
First purchase was 1k. 1982 2wd 1/2 ton The rusty one. Came with 10k on reman engine, a new radiator and an $800 set of front bucket seats. The guy was running it in his driveway and decided to bleed the fuel filter while running. He couldn't get it cranked again. Changed the filters, bled the air out and it ran for almost 2 years before it was scraped. It was so rusty you needed regular tetanus shots just to get in it.

Second was $1200. Another 2wd 1/2 ton 1985. 250k miles and just had the pump rebuilt and the tank steam cleaned. He drove it home and it wouldn't crank the next day so he sold it. The wires on the glow plug relay came off while at the shop and the mechanic put them back in the wrong places (the wires came out of the pigtail). Took 15 minutes to get it running. Still runs but getting near it's end.

Number 3. 1989 4x4 1/2 ton. $800. Rebuilt pump and 2 tractor trailer batteries. Towed my Honda toad home about 75 miles after purchase. Thought about turning this one into an off road toy.

Number 4 (and final) 1990 4x4 3/4 ton. $600. No engine but was originally diesel. Took the engine out of the rusty one for this one. Our current family vehicle.
We also have an 1986 3/4 ton 4x4 gasser Suburban. 9mpg on a good day. The diesels average 20+. Don't use veggie oil in the 6.2's or 6.5's as it doesn't lube the injector pump well enough and you will wind up having it rebuilt. You can burn used motor oil though.

The problem with the pump on the 6.5's is real and it only helps a little to move it. They still go bad regularly and we won't mind taking your money to rebuild it.

Edit:
Before you go putting a diesel in the body you have you might want to check out ebay for diesel suburbans and google "craigslist diesel surban" you might come out better just buying one that already has a diesel. Check out the Atlanta craigslist that's where I fould all of mine.