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671TA Detroit Diesel Overhaul & Upgrade

The Diesel Doctor

Subscriber
Last Subscription Date
12/28/2019
Hmmmm... There is an oil drain pipe that connects to the cylinder head to drain the valve area. It connects back to a separate reservoir in the oil pan, and a scavenging pump pumps that into the oil pan proper.

Keith
Pic #1 3rd photo down. AS the engine is horizontal the oil fill is on the oil pan. AL
 

Glenn Ayers

Subscriber
Last Subscription Date
02/18/2019
I remember the other thread. I wasn't sure this was the same project. The output unit on this engine kinda tripped my rememberer thing.

.
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Yes, horizontal, under floor, amidships.

Al, which engine were you wondering about? The bus that this engine is going in when it was built in 1955 was originally powered by a 779 ci Hall-Scott gasoline engine. I want to say 240 ish hp. Low speed, maybe 2200 rpm.

That was replaced at some point with an NH Cummins diesel, probably in the ‘70’s when 2 ~ 3 mpg suddenly became uneconomical lol. 220 hp, 2100 rpm.

The bus was originally equipped with a Silent Drive, which no longer remains, leaving it with poor traction. https://silentdrive.com/our-company/

These axles will be replaced with a conventional pair with an inter-axle differential.

Keith
 

The Diesel Doctor

Subscriber
Last Subscription Date
12/28/2019
Yes, horizontal, under floor, amidships.

Al, which engine were you wondering about? The bus that this engine is going in when it was built in 1955 was originally powered by a 779 ci Hall-Scott gasoline engine. I want to say 240 ish hp. Low speed, maybe 2200 rpm.

That was replaced at some point with an NH Cummins diesel, probably in the ‘70’s when 2 ~ 3 mpg suddenly became uneconomical lol. 220 hp, 2100 rpm.

The bus was originally equipped with a Silent Drive, which no longer remains, leaving it with poor traction. https://silentdrive.com/our-company/

These axles will be replaced with a conventional pair with an inter-axle differential.

Keith
Just curious, as to what it was powered with when it was last on the road. I had assumed it was a old 6-71. AL
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
One thing I’m concerned about is that I don’t think I have a bypass blower. That would seem to be necessary for maximum power and efficiency. Anyone who’s selling one is probably going to be really proud of it lol.

Keith
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
I wonder if this might be a more economical way to go? Appears to be a factory overhauled engine. Curious it doesn’t state the hp. It popped up in my saved searches. I think it started at $5k.
https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/362890842175

An acquaintance sent a link to this one
https://m.facebook.com/marketplace/item/485969751922254/

Not much info in either ad. Not going to buy any more engines until I have more completely evaluated the one I have. Will have another work session with it soon.

Keith
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
These service manuals belong to my friend, where we’ll be doing the work on the engine. To keep them clean, I have made a full copy of them at another friend’s wholesale print shop.

Will be up there again this Sunday and should be able to start the disassembly process.

Keith 05395A09-7974-47C9-B911-5DF8311FA0EB.jpegC783B76C-D555-496C-93A2-596614A0467F.jpeg
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
There was a delay, but finally got to work on the Detroit yesterday. Got all the external parts removed as well as the cylinder head.

This engine sat outside for a long time, so it was not surprising to find some rust. All of the gears are rusty. Maybe they could be cleaned up, but I would not trust them in this mission critical application.

I was also told that the engine had a knock in it when I bought it. There was nothing obvious in the bottom end, but finding a loose valve keeper laying under the rocker cover was the smoking gun. From there it was easy to find the valve spring with no valve, then a peek in the port revealed what was left of it.

The head appears to be damaged beyond economic repair.

I would imagine that the rod should not be trusted and could even be bent. What about the crank?

I think I’m going to keep an eye out for a running engine to overhaul. I need to get a parts book so I know what might best suit my needs.

Good thing is I now already have all of the Jake brake stuff, and all of the parts necessary for a horizontal engine. So I should be able to make use of just about any suitable vertical engine.

Keith 55351013-EFAF-4597-9BCE-F3031E3440BD.jpeg108C22A9-3B4E-4DAB-9E24-26388708B7BA.jpeg432D4C45-7170-46B3-BF0E-AA1B6726024B.jpegF8F440C7-20C5-432F-A2FD-D36B27FF6513.jpeg55351013-EFAF-4597-9BCE-F3031E3440BD.jpeg108C22A9-3B4E-4DAB-9E24-26388708B7BA.jpeg432D4C45-7170-46B3-BF0E-AA1B6726024B.jpegF8F440C7-20C5-432F-A2FD-D36B27FF6513.jpeg
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
I also forgot- four of the injectors were stuck too. Of course I can never know if they became stuck in the ten or so years I’ve had it sitting, or if that’s what caused the valve keeper failure.

There was also a lot of oil leaking from the blower seals. It’s all over the aftercooler and in the air box. So a runaway as the cause is not beyond the realm of possibility.

It appears to be a very high mileage engine. Heavy wear grooves on the crank sealing surface.

Keith
 

Birken Vogt

Email NOT Working
I just inspected a 4-71 the other day that was supposed to be a low hour runner sitting 10 years. One injector had the plunger stuck down in spite of the spring and the rack would not budge. Did not figure out why, left it to the owner.

I did have some success with one that was stuck one time. Held the bottom part in the chuck of a lathe, pushed the plunger slowly with the tail stock while running the little rack rod in and out and using WD40 on it. It ran fine and smooth after that but I understand it is "not recommended"
 
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