Starting a 671 Detroit after sitting for 35 years

We have a Ford N series semi with 671 Detroit that my grandpa parked after he ended his trucking business. I've heard countless trucking stories over the years, many involved Detroits. These motors intrigue me and I'd like to do some hands on learning. I'm not sure if it's worth the thought of starting it, but figured it'd be a good motor to learn on since it's no loss if I make a mistake. The truck does hold enough sentimental value that it might bring grandpa to tears if I saved it from be swallowed back in the woods. Grandpa said it ran fine when he parked it back in "about '79".

So can it been done?

Back then:




Now:

I'm also interested in this. I've found a truck that has been sitting for about 15 years and would love to make it run. Kind of a challenge to me. There are several videos on youtube of guys starting trucks that have been sitting. It seems like they change oil, all filters, clean fuel lines, fresh fuel, new batteries and ether. Good luck!! Post a video of the first start!

I'd pull the valve covers and check for rust content in the overhead. Check for easy rack travel etc so it doesn't run away. They go to full fuel after shutdown on their own, that's where it would rust up at. Vice grips on the rack are a good safety measure as well. Let's you control fuel after the governor.


Sent from my flashscan v2

will24 said:

I'd pull the valve covers and check for rust content in the overhead. Check for easy rack travel etc so it doesn't run away. They go to full fuel after shutdown on their own, that's where it would rust up at. Vice grips on the rack are a good safety measure as well. Let's you control fuel after the governor.


Sent from my flashscan v2

Click to expand...

What he said, I would find a way to get it some fresh fuel just watch the run away like he was saying


Sent from my iPhone using Tapatalk

YUP, assisted in firing an APC that had been sitting a while, and it went full rack... not a true runaway, but it can turn into one

thankfully, before we started it, I took the intake ducting off and had a square piece of 2x12 on the ready... even with the wood over the intake, it took a while for it to finally choke out

at the time I didn't know enough about them (still don't, honestly) to know how to manipulate the rack, but it was clearly stuck (pulled the valve covers AFTER we experienced the run away) and I told the guy I thought that was his issue

sure enough, they had everything gone through by a trained tech and got it running

Get a video!

My 3-53 sat for 5 years. I just got fresh battery's, fresh fuel and filters and she started right up!

But checking the rack and making sure you have a "stop" board will be a good safety measure to make sure she doesn't run away and go "boom"

exactly do all of what has been said. absolutely pull valve covers and put vice grips on the rack. at a 35 year sitter I would be taking extra steps to make sure a bearing doesn't spin on first crank. or break rusted rings.

I would personally pre lube the engine with an external pressure oiler. after the fluids and filters have all been changed. either tap into a main gallery port on the block. or the oil filter housing. and pressure fill oil through until you see it on the top end at each rocker. you can actually fill the sump that way if you wanted. I might even open up the governor and spray lube all the internal linkages make sure they're all free. pull the intake obviously and ensure its free of animal nests.

but in my mind do not turn the engine, not even by hand until its had a pressure lube. If you want a real chance of it surviving long term. not just short term running. the cylinders might even be siezed. actually theres a good chance the rings are stuck. after its been prelubed. try to turn it by hand first before you hit it with the starter. if its free perfect, give it a couple revolutions by hand. if not. you'll have to pull the injectors and fill the piston crowns with some creeping oil to free the rings from the cylinder walls.

If you just hitting the starter could break rings. or might stall the starter depends on how badly its rusted.

I want to see the video of start up too.

Thanks for that info Luke, that's valuable info right there. I was wondering if I could prime the oil system like we do with new motors. Grandpa mentioned that we should pull injectors and get some lube in the cylinders. Wish I had a Detroit veteran on hand for the "awakening" but with enough info we should be able to get it done on our own.

If and when it happens we'll definitely have a video to upload. First step is getting it out of the tree line and near the shop. A feat I may attempt this weekend when I'm back at the farm. Once we start diving into this project I'll be taking pictures along the way.

That's a cool truck. Would be awesome to see running again. Is it a 6-71 or 6v-71?

If you wanted. It wouldn't hurt to pull the airbox covers off and inspect the airbox condition and if you have a bore scope you can inspect the bottom of the blower. And there will most likely be a couple cylinders you can scope inside the intake ports. It will give you an idea how much rust is actually on the cylinder walls and what the piston crowns look like.

I have a pressure bottle built from an air tank. I use it for fuel to prime engines. But it pushes oil just fine too.

It's an inline 6-71. Once we get it up to the shop I'll update with some shots of the motor and everything. I'd love to resurrect this thing and boom around it in, hell, might even tow my little gooseneck around for fun if we get it going.

Do they have any way to spin the oil pump like we do on gas motors? I'm sure we could rig something up with an air tank though. Do you regulate the pressure down to 20psi or something?

No the oil pump is gear driven by the crank gear.

You regular the air pressure to your vessel yes. But more than 20 psi. As long as you stay below relief pressure let it buck. Best way is to pull a main gallery plug put a fitting in place. And hook your tank discharge hose to that fitting.

You know you cannot use multi weight engine oil in Detroit 2 strokes right?

Only w30 or w50 depending on your climate.

I don't know anything about 2 stroke Detroits, I'll take any info I can get. All I know is keep a board handy to keep them from running away after they sit.

Right on. Ya I'll help you out however I can. And I should have said w30 or w40. Straight weight. You probably want to think you can run multi weight just because it makes sense. But you can't. Has to be straight weight for a 2 stroke compression ignition rating.

Ran 15-40 in thousands of military trucks with 8V-92TA's in them with no problems...

I bet they did.

It's much like a fat chick wearing spandex. Just cause you get away with it most times doesn't make it right.

I can see an outfit like the military running the wrong oil intentionally just for standardization purposes it's cheaper for them to yard one out when it fails than stock and extra oil.

The only reason GM says that, is because they did a study back in the day, and AT THAT TIME, the multi viscosity oils available did not meet requirements. Some were running 10w30 instead of 30w, and that particular oil didn't meet the 30w spec when warm (more like 25w). With modern oil you'll never see an issue. Has nothing to do with it being a 2 smoker. Its still compression ignition.

1-10-2015 671 gets fresh oil change then runs away

Howdy

I've had a 24 valve for about 8 years now in 6 speed manual. Has all of the tricks done to it and its a real screamer.
Such a reliable machine.

Just wanted to let everyone know I also have a 671 detroit 2 stroke that I play around with. Today 1-10-2015 I changed the oil in the 671 Yes 7 gallons of oil.
Started it and it and the thing ran away immediately.
Scared the Holy Heck out of because the truck has no cab and the exhaust is straight piped and comes out right by where the cab used to be.

Luckily I already had the air cleaner off and a steel plate laying by just in case it ever decided to run away.
Was a sad day because after several years it had never run away until today when I put fresh oil in it.

I had not been that freaked out in a long time.

Guess I am now part of the diesel runaway club.

I'm thinking that it ran away because the linkage stuck, but when I was using the foot throttle I could see the external linkage all moving and retracting.

It breaks my heart to think the cylinder walls are leaking oil and that the motor needs a rebuild, again it has never done this before until the fresh oil change.

I might try to fire her up again and have a helper work the starter. Its just weird being in the city and such a gear head because I know no one that is into hotrod diesels or large diesel engines.