Any info on the 6-71 Detroit?

[RampageFSJ]

I'm looking at a toterhome that a guy has for sale. The chassis is a 72 with an 86 cab on it. He told me that the engine is a naturally aspirated 6-71 six cylinder Detroit diesel. From my research so far, the 6-71 is a two stroke engine and likes to make its power with high rpm's. Because they're two stroke, do they need any special treatment with the fuel or not? I've also been led to believe that they have a supercharger if they don't have a turbo (not completely sure on that one though). I've also seen that Detroits (not just the 6-71) are notorious for leaking oil.

That's pretty much all that I've dug up on my own. I was wondering if there's any more details about the 6-71 that I should look into? The current owner doesn't know exactly how many miles are on the truck because the odometer has been broken ever since he bought it. He says it has no leaks aside from a small power steering leak. He also told me that it can't go over 70 mph with the 9 speed in it but it will pull anything.

Here's a picture of the truck that I'm referring to.


Any help is greatly appreciated.

[spreader]

All of the 2-stroke DD's have superchargers. But, they still call them NA(naturally aspirated). I have never seen a 6-71 with a turbo, but I haven't seen them all. It's not untill you get in the V-8's that you will see a DD with a turbo. And , then it still has a supercharger on it. You're right about the horsepower. DD's worked best at the upper limit of the RPM band, around 2200 to 2300. Don't ever lug the engine.
The 70MPH limit is due to the rear-end ratio. An RTO 910 would be good, but not enough to justify the money. I'm not 100% certain, but I think an overdrive unit could be added to the tranny. But, I dont think you have the horse for it. I don't quite beleive the "pull anything". looks as if you will never see a heavy load tho.
And, yes, they are known for leaking. But it don't have to be that way. A good PM schedule and going over it routinely will keep it clean. At the same time you do an old Harley pan-head..
Fuel usage should be around 4 MPG. Maybe a little better. In the winter find where they sell winterized diesel. There are additives for the fuel to prevent gelling. And, I know it gets cold there in Ks. Been stuck on I-70 with road closed. A block heater will be advantagious.
Good luck with it if you buy it.

[Yeahright]

Two Stroke Detroits Do not have superchargers, They Have Blowers. they are required for the engine to run because they are the only thing that will push the exaust out the exaust valves and fresh air in through the ports... The power will be on the upper end of the rpm range And dont be afraid to run on the governor, chances are it will pull anything you ever put behind it but dont expect it to be a speed demon with the Natural engine.

[RampageFSJ]

Originally Posted by spreader

All of the 2-stroke DD's have superchargers. But, they still call them NA(naturally aspirated). I have never seen a 6-71 with a turbo, but I haven't seen them all. It's not untill you get in the V-8's that you will see a DD with a turbo. And , then it still has a supercharger on it. You're right about the horsepower. DD's worked best at the upper limit of the RPM band, around 2200 to 2300. Don't ever lug the engine.
The 70MPH limit is due to the rear-end ratio. An RTO 910 would be good, but not enough to justify the money. I'm not 100% certain, but I think an overdrive unit could be added to the tranny. But, I dont think you have the horse for it. I don't quite beleive the "pull anything". looks as if you will never see a heavy load tho.
And, yes, they are known for leaking. But it don't have to be that way. A good PM schedule and going over it routinely will keep it clean. At the same time you do an old Harley pan-head..
Fuel usage should be around 4 MPG. Maybe a little better. In the winter find where they sell winterized diesel. There are additives for the fuel to prevent gelling. And, I know it gets cold there in Ks. Been stuck on I-70 with road closed. A block heater will be advantagious.
Good luck with it if you buy it.

Thanks, I'm not bothered by the limit of 70 mph, at least I wouldn't get caught speeding. It has an Eaton 9 speed in it according to him. My heaviest load would probably be three trail rigs at roughly 3,500 a piece, but two would be the normal load. It can fit one in the back and it has a spot between the lift gate in the rear where I could put a hitch. I'm mainly looking into it as a replacement for my dually that would be cheaper to insure and register as well as have a living quarters.

I haven't ever come across a place around here that sells winterized diesel. If I were to get it, I probably wouldn't use it untill I put a toilet and running water in it to make it qualify as an RV in Kansas. Somehow he has it registered in Georgia as an RV even though it doesn't have a sink or toilet.

[DURAtotheMAX]

Originally Posted by Yeahright

Two Stroke Detroits Do not have superchargers, They Have Blowers.

remind me again what the fuck the difference is between a supercharger and a blower?

ben

[hy_desert_4wheeler]

Originally Posted by DURAtotheMAX

remind me again what the fuck the difference is between a supercharger and a blower?

ben

that is pretty much what I was thinking then I looked at his post count I think he needs to go back to grade school..

[nightcrawlers]

yeah im waiting to be educated on this blower/supercharger thing as well.

rampage,that thing is bad ass. how long is the box? any pics of the inside?

[TR]

Wow a text book answer on how a 2 stroke DD works. What tech school are you attending? Any way guys a supercharger raises the manifold pressure above atmospheric and a blower does not. Physically they are the same it just depends on what they are bolted to determines the differance. Kinda like a turbocharger & a altitude compensator

[demonranger]

They are great engines will run for quite a while, they like to mark their territory and burn a bit of oil too even from the factory. They do not get stellar fuel mileage, search for sceep's post on his fire engine tow rig. Granted his is an 8 cylinder but still do not expect much better mileage.

[rockdog57]

If the truck rolls backwards when the engine stalls. You just let out the clutch in forward gear and they start up backwards. Watched more than one concrete truck driver back in the day do that. Cleans the air filters right out. Damn funny to watch too.

[RampageFSJ]

Originally Posted by nightcrawlers

yeah im waiting to be educated on this blower/supercharger thing as well.

rampage,that thing is bad ass. how long is the box? any pics of the inside?

The box is 23 foot, 4 inches long. The hauling section of the box is 16 foot, 8 inches long and 95 inches wide. The racks are for his dirt track tires.

[Yeahright]

Originally Posted by TR

Wow a text book answer on how a 2 stroke DD works. What tech school are you attending? Any way guys a supercharger raises the manifold pressure above atmospheric and a blower does not. Physically they are the same it just depends on what they are bolted to determines the differance. Kinda like a turbocharger & a altitude compensator

Portland Community College, but I didn't learn much about the two strokes there... I work on this On The Weekends (slightly modified 16v92TA)



sorry I didn't get back to the other guys sooner

[spreader]

rockdog57
Having the damn thing start running backwards at 2A.M. after a short nap eat'en the horn button will definitely get your attention. Twice!!

And, look at those purty 'altitude compensators'. 2 to the side, no less!

[crashnzuk]

That interior needs a disco ball and some cash money ho's doing lap dances.
Travis..

[RampageFSJ]

Originally Posted by crashnzuk

That interior needs a disco ball and some cash money ho's doing lap dances.
Travis..

Don't lie, you'd pimp it.

[nightcrawlers]

i would!

[crashnzuk]

Originally Posted by RampageFSJ

Don't lie, you'd pimp it.

I never said I wouldn't, just that those things are missing
Travis..

[powerstroker01]

all 2 stroke dd's have blowers(53,71,92) some 53's have turbos,some 71's have turbos and all 92's have turbos.. Run it on the governer you wont hurt anything

[WTF-J]

Originally Posted by Yeahright

Two Stroke Detroits Do not have superchargers, They Have Blowers. they are required for the engine to run because they are the only thing that will push the exaust out the exaust valves and fresh air in through the ports... The power will be on the upper end of the rpm range And dont be afraid to run on the governor, chances are it will pull anything you ever put behind it but dont expect it to be a speed demon with the Natural engine.

Where you come from, they may be called blowers, but in my neck of the woods the twin screw Roots type thingies on the intake manifold are called superchargers.

Have a good life.

[speedo]

Originally Posted by WTF-J

Where you come from, they may be called blowers, but in my neck of the woods the twin screw Roots type thingies on the intake manifold are called superchargers.

Have a good life.

Well there you have it, the blower on a 6-71 doesn't sit on an intake manifold. It is bolted to the side of the block and feeds into the air box.

Gus

[chunky]

the 6-71 i worked around logging was damn reliable (may sound wierd i know) but it was in a log loader (like an excavator) that was at full throttle for hours and i never had to work on it once in the year it was there. looks like a cool find

[K-TRON]

The 6-71 is commonly known as the 238 detroit.
There are a few variants of the 6-71 out there
The earliest were the 6-71's made by General Motors Diesel - Pre Sale to Detroit Diesel
A 6-71T was added to the lineup in the late 1950's, which brought its horsepower up from 220-240 to 280hp
Somewhere in between 1975-1990 Detroit came out with a DDEC 6-71 which dinos 485 horsepower.
The series 71 dates back to 1938.

The 6-71 is a big engine, takes up the same length as a 12V71. You can get some serious power out of them with an injector swap, and a turbo upgrade.
They run quite a while.
I went to the ATHS truck show out on Macungie PA, this summer, and one of the crackerbox 6-71's had over 700,000 miles on it.

The two stroke detroit is a pretty reliable engine, a dinosaur today, but they can be rebuilt very easily. I have heard of many people taking seized detroits and having them run like new again.
Its very simple to do, albeit expensive, but that us possible because the liners are removable, which is advantageous over a bored out block. That way it can restored to new.
They are fairly simple to work on cause there is no electronic crap all over it.

If you are really focused on getting better mileage, I suggest researching a bypass blower for your 6-71 supercharger. They attach to the endplate. Somewhere around 8mmhg or psi (cant remember), the airflow is directed around the supercharger, essentially making more horsepower. It is known that the addition of a by pass blower can free up 30-40horsepower.
But then again, if you want the bypass blower, you need a turbocharger.

If you have never worked on a Detroit Diesel, I suggest getting the inline Series 71 manual, there are two binders
1 with section 1-3
and the second binder has section 4-15

If the answers you are looking for cannot be found here, I suggest going to the Detroit Diesel Yahoo Groups, there are hundreds of Detroit guys there who will be more than happy to answer all of your questions.
There is also a small subforum for Detroits on the Cummins 4BT swaps page

Chris

[WTF-J]

Originally Posted by speedo

Well there you have it, the blower on a 6-71 doesn't sit on an intake manifold. It is bolted to the side of the block and feeds into the air box.

Gus

You're having way too much fun splitting hairs on this one. Air box is part of the manifold.

[RampageFSJ]

Thanks a bunch for the information. I'm starting to think that I'm going to pass on the truck now. For some reason, the owner hasn't been answering his phone when I called him several times this weekend and he never sent me the pictures that he said he took on Friday. What irks me is that when I called his shop and an employee said the owner was away, he told me that his cell phone was working fine since he had just gotten done talking to him on it before I called.

I'm not sure if he's sold it and doesn't want to bother with me or what, but I'm not sure I want to deal with somebody who won't answer the phone for a potential buyer. Either way, I'm probably going to pass on this one and concentrate on building a shop.