The Stovebolt Site Forums The Shop Area Engine Shop 6.5 Diesel

How do the 6.5 diesels compare to the Cummins 4bt as far as reliability and life span? I was looking at Dovebid today and the P30s with the Cummins seem to be disappearing fast, almost everything listed was the 6.5.

Poor on both. The 4BT's sell for more and quickly for a reason.
Learn about them at www.4btswaps.com

Some folks say the 6.5 will hold together and make good power, and ocasionaly they do, but most everyone perfers the 4BT given the two choices.

Pick an engine you will be happy with, and one you will enjoy working on.

Grigg

Thanks Grigg. That's what I thought. I better snap one up before they all disappear.

There is no comparison. Cummins is actually a well designed diesel, the 6.5 is nothing more than a gas car engine. Never should have been built.

Crabby:" the 6.5 is nothing more than gas car engine. Never should have been built".

I beg to differ and apparently so do the US Armed forces as they still use it in the extremely successful Hummer. It was designed by Detroit Diesel and from the beginning it was a diesel...NEVER was a Gas Engine or a Car Engine. The engine is still in production after 12-13 years so how do you explain that? There are lots of versions of it as there are with all successful engine series.

The 6.2/6.5 diesel was OK as long as you don't pull them too hard. We had a 1982 Chevy 4WD dually we used to pull a tub grinder around with. In stock form (6.2) it wouldn't pull the hat off your head, so we put on a Banks turbo. This helped somewhat but then it would overheat easily and head gaskets became a problem. We then upgraded to a 6.5, which was built for a turbo. This helped somewhat, but a Dodge 3/4 ton with a 5.9L Cummins would leave the dually in the weeds every time and burn less fuel to boot.

We had two other pickups with 6.2s in them and we got along with them OK--fair power and economy but they were nowhere near the diesel the 5.9 Cummins is.

The 6.2 is a converted gas engine. But the 6.5 is a true diesel. Many companys still use them because they are reliable engines. The only problems I have heard of them having is the fuelpump going out.

The 6.2 and 6.5 are the same engines, the only diff is the 6.5 has a better crank. The 350 diesel was a car engine. I had an 85 K10 and my father had an 85 K30. The 6.2 was a workhorse, but not too highway friendly. They wouldn't get out of their own way to save your soul. If you are planning on running around town or working on the farm they are great. My K10 had a 700R4 trans. It was kind of a dog at first, but I rebuilt the trans. and put a shift kit in it. What a difference! You almost didn't even know you were driving a diesel! I still regret selling the truck. I'd like to find a 6.2 or 6.5 to throw in an old 'bolt. Maybe someday...

I know you thought I was thinking of the first GM car diesel, built upon the 350 Olds foundation, but I was not.

I know there are differences, but wasn't the 6.5 built more or less on the big block Chevy? That is a fine gas engine, but it won't cut it as far as a diesel goes.

I could be wrong though, I have been before.

Unfortunately this time you are, and no, I was not thinking of the Olds 350 variant.

Well, I didn't know that. I only saw one apart once, I thought it was a big block Chevy just looking at the block and rods. The mechanic said it was a 6.2 or 6.5, can't remember which but he said they were similar to a big block Chevy so that is what I was going on. I know they aren't a bad engine, just not comparable to the Cummins.

The 6.5 is built just for work you dont get alot of power out of them. But the 6.2 does look similar to a 6.5 GM was trying to get away from the Olds diesel. But I would go with a Cummins you can get alot more power out of them. And it would look more authentic since its a straight six.

I agree. The 6.2 & 6.5 are basically the same engines & were designed as a diesel. There reliability on average is not very good & they are sluggish, although we have been running one in a roll back that must have 300,000 or more miles on it. It still runs good. The 4BT is noisy, smoky, shaky, & slow but are tough.

I own a 6.5 powered pickup.... When my Bolt is all done, that 6.5 is out of there and I'll replace it with a 4BT. The 6.5 has more horsepower, but about the same torque, less fuel economy, and way higher maintenance........

I for one won't bash the 6.5, but I sure wouldn't go to the work to convert one into a vehicle.....

Here is the official answer from a former Diesel manufacturer employee (Read that as a former Cummins Employee). The 4B and 6B family of Cummins engines are heavy duty, continuous use Mid-Range powered engines, while the 6.2 and 6.5 are automotive based light duty diesels. The Navistar (Ford Power Stroke) is also a light duty diesel, so is the up-comming LDD from Cummins (Light Duty Diesel) that will be powering the 1/2T Dodges

That being said, you can beat the pi$$ out of a heavy duty continuous use diesel 100% of the time, while a light duty diesel has a lower duty cycle, more like 10% at full load, 25% at 50% load, 25% at 25% load and 40% of its life at light to no load.

The 6.2 and 6.5 are not related to the Olds 5.7 variant that GM had in the mid 70's, so the block failure issue is no longer a concern

If looking at the 4B, check with your local Cummins distributor as you can get them for much less than any of the auction sites. Also the Echo engine (4-valve ISB variant) that was slated for Euro use was used in the US in UPS and Fed EX trucks in the early 2000's Much more power. Those engines have rear gear train and were the predecessors to todays QSB industrial engines.

Personally the 4B needs a balance shaft like the Deere 4.5 liter to prevent the 3rd, 4th, and 5th order harmonics from rattling the engine apart. The 4B is also known as the "paint shaker" as it shakes like a dog passing a peach pit. Although the marine double dampers help it. The 6B and QSB engines are bullet proof, smooth, and in non-100% duty cycle mode can make a crap-load of power with twin turbos, etc. Hence the superiority of the Dodge trucks with the Cummins Diesel. Unfortunately 6 cylinders in a row are a bit long for some conversions as compared to a V engine.

Unfortunately they all are assembled by humans and subject to failure eventually.

As Grigg stated, pick an engine that you will be happy with and live with that decision. In an automotive installation, both will run for a really long time with proper maintenance, and both will die fast and painfully without proper maintenance.

Scott

I agree with all points mentioned except a few:

First, the 6.5 DOES have block cracking issues..... Run any power into them and watch the block split.... Actually, the 6.2 block will hold more power than a 6.5......

Heads: They will crack eventually.. I count myself EXTREMELY lucky to have an old-style head(s) on my 95 and still have them in one piece.....

IP's: The POS stanadyne DS4 electronic injection pumps are a nightmare..... All the issues I have EVER had with my truck (and I've had many....) Have related DIRECTLY to that junk pump and or it's supporting hardware.. I personally wouldn't own another vehicle with Stanadyne anything in it..... At least not their electronic stuff........

Design: Being an indirect injection system, these engines are not going to acheive the efficiency levels that a DI engine, such as the Cummins, Duramax, and Powerstroke.. Plus, due to the higher compression ratios needed on IDI engines, they start harder. (My truck is in VERY good condition internally, and it WILL NOT start if you don't wait for glowplugs..... Our ancient DI Massey-Fergusson with a Perkins diesel will start clear down into the 20's. And it has no glowplugs, nothing....)

Cooling: Because of the IDI, primary combustion occurs within the head. Thus, all IDI engines run HOT. If you've ever seen the radiator for a 6.5, they are the same size as the towing-package suburbans and 454 powered vehicles.... Them babies push out some serious heat.... That heat is diesel fuel that isn't moving your vehicle down the road....

So, in short; like I said before, I won't bash the 6.5, but I certianly would pick a better engine if I was contemplating a swap from scratch..... Now, if you've got a good running free 6.5 laying in your garage, then go for it! With the money you'll save not buying a cummins and tranny adapters and such, you can put so good mods into the 6.5 to get the torque, fuel economy, and reliability up a little....

I was laughing when I read 53moneypits comment on the 6.5, "its good enough for the armed forces". A friend of mine was a mechanic in the marine corps. Of all the things he did they were very efficient at changing diesels in the Hummer. The Marine Corps has there own engine shops and the 6.5 is the only rebuild they can't keep up with! It gets contracted out! lol