History 671 detroit diesel questions

We had them in 4 7220 American cranes and 8 Ford LNT 9000s. They're almost indestructible, will run on almost anything and will start in cold weather. One 20 below morning they decided to start one crane that hadn't been run for a month to break some cast iron. They tried starting fluid but could only get it to pop a few times. Finally they noticed that the emergency shut off was tripped. When it started, it took off. I was in the shop over 100 feet from it and it sounded like someone had a snowmobile cranking wide open with the track lifted right outside the door. It slowed down when it used up the starting fluid and the only damage it did was destroyed the tachometer.

We ran the crane engines 8,000 to 10,000 hours and the truck engines 100,000 to 150,000 miles. You should only run straight #30 weight oil in them or they will use lots of oil. 15w40 goes right through them.

 

Yeah, Dad always said you could run a 71 right up against the governer all day long and it would be just fine.
...and that's very true about the oil.
The nickname "driptroit" came from the fact that not everyone knows that.


6narow

 

Make sure you bring your 5 gallons of oil. You ll need it every time you stop. They sure loved to mark their territory with oil puddles

 

...see what I mean?

 

I remember these motors from 2 fire trucks my former vollie fire dept had. Both were 72 model Ward La Frances. One had an automatic and was a dog. The other had a 5 speed manual, 500 gal tank, had to be double clutched and would run 80mph with enough road. that truck felt like a huge muscle fire truck.

Loved driving that 5spd truck. I thought chief was crazy when he said you had to drive the snot out of it constantly. if it wasnt kept on boil or hit 5th instead of 3rd gear it fell on its face. You could hear both coming down the road from a mile away.

I started driving both in 2001 and the second one was sold off in Jan 2008. Guy that bought it drove it to California from south Alabama. Long and loud ride.




Posted from the TJJ App for iPhone & iPad

 

Detroits have a great history if nothing else.They powered alot of military stuff in WW2 . In the beginning of Saving Private Ryan you can hear the Detroit wail from the landing craft.
I've driven Detroit powered dump trucks and you go like hell until the first hill,then down shift like crazy.Very reliable powerplant of the of 50-60's GM city buses.

 

Got a good 6v92 silver edition if you have the room for it. 350 hp. Won't be bad on mileage neither down in south texas thanks

 

Place I worked at had an old army surplus Lull [overgrown 4 wheel drive forklift] with a 6-71 Detroit. Ran like a top until one day it blew a head gasket. I pulled the head to see a circular indentation on the bottom side of the head where the sleeve had come loose and began going up and down with the piston...beating the bottom of the head. I had the cylinder head surfaced and put it back together with a new head gasket...ran like a top again 'till we replaced the machine years later.

 

Crown used these motors laying down under the bus, the same with a Cummins, there are some differences between the pancake engines and the vertical, you won't put anything else in its place without major work as there isn't enough room under the floor for a stand up. As was said earlier the later ones had 4 valve heads and were a little better, I have a couple heads and blowers they can be converted, as also was mentioned use 30 wt oil only, driptroits do not like multi vis, Detroit came out a few years ago with a message to not use a multi vis in the old engines as it would raise hell with the cross head pistons. A 10 spd trans will help and keep it wound up tight, it'll run for years.

 

I remember watching that movie that thinking that they got that wrong, because as far as I know, landing craft were powered by flathead Studebaker Champ sixes! Same engine they used in the Weasels!

--------------------------------------------------------------

Rocky,

That must've been an old engine. I think DDA replaced their one piece head gaskets with ring sets, in the 50's!

 

There were several types of landing craft and ...The ones used during D day had Grey Marine Diesels (6-71 GMC ) or a Hall Scott 250 hp gas engine according to Internet info.. ...I would think a landing craft is too heavy for a car engine.

 

I don't know, its what Dad used to say.
I did take a peek at Wiki's "WWII Landing craft" page. I had no idea that there were so many variations.
When I was growing up, any old-timers that mentioned them, usually called them "Higgins Boats", regardless of vairent (with exception to Amphib's and landing ships).
Anyway, thanks for bringing that to my attention.


6narow

 

Hello everyone and Happy Easter! Stumbled onto this forum and find it quite interesting - so I joined. I have a '57 GMC transit bus with its original 671 Detroit that I had rebuilt. Soon after the rebuild, the bus began stalling each time it tries to shift into second (hydromatic trans). Does anyone have insight on what would cause this? Thanks

 

I owned and operated ,a '48 GMC 3751 bus( ex Grayhound Silver Side). I did a motorhome conversion on it in 1975. It was a life boat during some hard times, full timed in it for a few years and was used as a Rv until 1990.It had a 671 with a 4 speed gearbox
and was well maintained. I always used 40wt.Delo and had almost no oil leaks. Usually
got about 10 to 12 MPG, except in the mountain passes, then I was looking at 5 to 6 MPG. The only drawback was the lack of power steering, it was OK at speed,but a real
problem when you were stopped.The other problem was a place to park it,if I didn't have space at my home, then they become like a boat or air plane and it's usually not cheap.

.....................Jack

 

I have put several detroit's in farm tractors. You may have a "low block" there, might be a good one to stay away from. Way to tell is look for a small notch in the top of the block just under the head on each end. Later high blocks will have the notch, it is part of the machining for the oil oring. In lines (6-71) are easier to rebuild than v's (6v-71) not near as picky on fitting the sleeves. All detroits were very generous with there power rating, power is peaky, not good on hills, not good for lugging. They work great up against the governor all day like in a boat or a farm tractor. I found that if you put a detroit with a rating 50% greater than you needed you would be happy. If the engine was rated at 238 horse like a N series 4 valve 6-71 and you need 238 to get the job done you will not be happy.
I also run a transit maintenance shop and not to spoil your plan but you may have more potential work there than you may want. Although I think the old crowns are pretty cool.
That old a bus may have things like copper brake lines, no back up if you loose a brake air line like the post 1976 trucks and buses have (dual system). Also a pancake as I am sure you have figured out is a engine laying on its side, bit of a stinker to work on if you don't have a hoist big enough to lift it.
I will be interested to see what you decide. Best of luck to you either way.

B

 

Hey Ralph, When the governor tells the magnet valve to move the clutch arm, it also send an air signal to either a stop valve on the right side of the head or it sends air to the engine stop valve atop the governor. It should shift fast enough so the engine dosen't die in the mean time. If the air pressure is low to the shift cylinder, it will not make the shift, or take too long. There;s a pressure regulator there at the shift magnet valve and should be at 60 psi for the shift to happen right. could be the seal ring in the clutch shift cylinder is leaking real bad and can't build up enough pressure to make the shift. Or the direct clutch is burnt up and it has no direct. that will also stall the engine. Or the neutral solenoid arm is stuck in the up position keeping the clutch arm from full travel.
You need a maintenance manual or an old fart close by to look at it.

 

Hey I think a Crown bus with a deetroit is cool and you can do things to make it go faster and more power. Like some of the guy's said, nothing sounds like a jimmy up against the pipe. But like anything else old, the old timers that know that stuff are getting harder and harder to find. That and you make more hp you make more heat and deetroits don't like heat.
AND you are trashing my avatar talking down the old detroits.
It is a 6-71 I laying in a cradle on the ground getting ready to go back into a '56 GM 4104. I built it turbocharged and found an after cooled block. That and a 3.56 rear end gear change and it does real good getting down the road. 325hp and 760 ftlbs torque.
That from a 426 CI engine with no carbuerator and spark plugs
Doesn't slobber oil, like anything else it is in how you build it.

It gets work as a picture bus and if you have seen the Las Vegas show on CBS it is in it multiple times

That and I have a 92 series that has 300k miles on it and it uses a gallon of 40wt Delo 100 every 5000 miles. No slobber either. Don't know if it is HAMB friendly but there is a photo of it pulling my T'all (the regular towed) and one of the engine when it made it into the 4104.

LJ