Detroit Diesel 671TI Rebuild

thelast322 · Post by **thelast322** » Mon Dec 27, 2010 2:27 pm

Sorry~ Maybe I missed the boat on another thread, but why the rebuild. Are your engines a little tired? How many hours did you have on them? Not trying to be to demanding on the questions, just curious. Totally understand the have some good years of service accrued.

Thanks
Butch

Jerry · Post by **Jerry** » Mon Dec 27, 2010 3:44 pm

Butch,
Engines have just over 1100 hours on them.
Starboard engine has always run fine. Port started to smoke constantly and picked up a heartbeat that you could feel at an idle. I also started to get a bit of a sheen on the water.
Thought maybe it was a bad injector but after canceling it out and verifying the cylinder, replaced it and it still had the issue.
Removed air box covers and used a borescope to take a look and did not like the way the cylinder walls looked.
Did a compression check and had 1 cylinder that was down to 300 lbs. That is not enough compression to ignite the fuel oil, thus my problem.
I did do a compression check on the other engine and all were right around 480-485 so all is good there.
Even doing a compression test on these engines is quite a task. It is just not as easy as taking out the sparkplugs as on a gas engine.

Jerry · Post by **Jerry** » Mon Dec 27, 2010 6:14 pm

We put another temporary piece of flooring in here and got the head ready to lift out.

Here is what we have been working on to lift the engine up a couple of feet.

We are using a couple of mini chain falls that are rated at 2,000 pounds each so they should work just fine.
I was going to use the strap type come alongs but they do not offer the adjustability of a chain fall.
This weekend should be interesting.

Jerry · Post by **Jerry** » Mon Dec 27, 2010 6:23 pm

We need to lift the engine just a bit to get the tranny to slide back. I unbolted the shaft coupler and slid the shaft back as far as I could to give us some room.
The shaft went back to the point that I was about to hit the rudder with the prop.... but I ran out of room between the coupler and flange at the same time so that worked out well.
I plan on supporting the engine with large blocks across the stringers when we get it the the proper height so some of the load will be on the blocks and some on the lifting chains.
That will be easy in the front until I remove the front cover as the mounts are bolted to the cover.
In the rear it will be a bit tricky as the rear mounts are actually on the tranny and not on the block so once I remove the trans, no more mounts.
A lot of this will have to be fabricated on the fly.

prowlersfish · Post by **prowlersfish** » Mon Dec 27, 2010 7:08 pm

Unless you need to pull the crank or rear seal , you can leave the gear on If I remember correctly .

Jerry · Post by **Jerry** » Tue Dec 28, 2010 8:28 am

As long as I am this far, I am going to replace the rear main and front seal just to give me a piece of mind.
I am hoping that I can just loosen the main caps and roll the upper main bearings in place as I would hate to have to remove the crank. I will see what the journels look like and make up my mind from there.
With the low hours on the engine I don't forsee any problems..... Maybe I shouldn't have said that.

prowlersfish · Post by **prowlersfish** » Tue Dec 28, 2010 8:43 am

The mains should go a lot more hours the the piston & liner kits . Make sure you check the old bearings to make sure your replacing it with the same size .

rossjo · Post by **rossjo** » Tue Dec 28, 2010 10:34 am

Jerry wrote:They make the sleeves in .001 oversize increments so you hone the block just enough to clean it up and then measure, measure again and when you are all done you measure it one more time.
Originally, Detroit wanted about .000-.0025 between the block and the sleeve but I am being told that it should be a bit tighter than .0025 being a dry sleeve and that tighter fit will drastically cut down on the high-low pressure areas. We will be shooting for the low end of that range.

So you'll hone the block while in the boat? How do you plan to do this?

thelast322 · Post by **thelast322** » Tue Dec 28, 2010 11:06 am

Jerry,
Good for you on concording this large time consuming Task. You are really kicking butt and getting it done right. Just think how nice it will be this season when your cruising done the waterway with those Fresh Detroits. Looking over your project allows me to realize why a shop would charge you 2 arms and a leg to do what you are doing. "They still charge too much"

Back in 2006 I pulled my 2 350 CID Crusaders out to get the Stringers replaced. One engine was rebuilt due to sub-par compression reading and me being extremly eager. I stripped the block and sent it to a machine shop. So my point is, I kinda can feel your pain. The big difference was it is a lot easier to get those 2 gas blocks out of the Sedan compared to the monsters you have in a Aft cabin. Back in 1992, when a was a young fireman apprentice in the Navy; I had the pleasure of helping a rebuild job on a 6V-Mtu. Can't remember the CID but they were like 700+ BHP. I remember dropping the pistons down beneath the block . The heads were around 75lbs ea and were individual for each cylinder. I remember messing with the journal bearings but don't know if we pulled the crank. We did it in place in the engine room. I was a new guy and they used me from the neck down if you get my drift. These were auxillary lift engines for lift air on a 160ft Surface effect ship. the mains were 16v Mtu over 2000hp each.

Thanks for the great post and keep up the good work!
Butch

Jerry · Post by **Jerry** » Tue Dec 28, 2010 11:18 am

prowlersfish wrote:The mains should go a lot more hours the the piston & liner kits . Make sure you check the old bearings to make sure your replacing it with the same size .

I have gone back and forth on this for a couple of months now as I have been told by people that know a lot more than I do to just leave the crank alone. Just as you said those mains will last a very long time.... But.... I guess I am just goofy that way as I would lose sleep knowing that I went this far and did not put new ones in.

Jerry · Post by **Jerry** » Tue Dec 28, 2010 11:24 am

rossjo wrote:
Jerry wrote:
So you'll hone the block while in the boat? How do you plan to do this?

I have an adjustable power hone that I will use.
You cannot use the normal spring loaded hone is it will make a mess out of a cylinder very fast.
As long as you use the proper grit stones and keep them clean..... and DO not be too aggressive it should all clean up fine. I think Detroit calls for 75% clean up with no low pressure area to be larger than a half dollar.
I will know for sure once all of the sleeves are removed and I get to work with the micrometer.

Jerry · Post by **Jerry** » Tue Dec 28, 2010 11:42 am

Butch,
I know what you went through with the stringer replacement as a couple of guys did it down at the club that I am in. That is also a major job that I would not look forward to.
On the 10 meter that I had I also pulled both engines and generator to rebuild. I would much rather do that again than do what I am doing now.... But I do enjoy the challenge and learning something new.
It sounds like you have some diesel experience. What are you doing for the rest of the winter?

thelast322 · Post by **thelast322** » Tue Dec 28, 2010 7:31 pm

Jerry, If I was not 6hrs away, I would love to turn some wrenches with you!!!!!!! That is what it is all about, helping others and learning new things.

Now is the time you can call of those people you took out in the warm summer and tell them to come down to the boat to see why your boat runs so good when you need it the most

rossjo · Post by **rossjo** » Wed Dec 29, 2010 9:38 am

Jerry wrote: I have an adjustable power hone that I will use.

Nice - those Detroits will love you for your efforts.

Jerry · Post by **Jerry** » Mon Jan 03, 2011 11:27 am

Wow.... That sucks.
I lost two pages of pics and comments.