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Old 08-05-2020, 03:57   #1
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perkins 4-108 Break In after Rebuild

Looking for advice from the folks who have rebuild experience. I just finished a rebuild on my Perkins 4-108 (with lots of advice from this forum-thank you!) Engine is running on the bench at varying rpms as I run it for the first couple of hours before retorquing the head and giving it an oil change. 55 pounds of pressure, no oil leaks and maintains temp at 180 at 3/4 throttle.

The engine is running smoky. Is this a break in thing or could the fuel pump timing alignment need minor adjusting? I only bled the pump and two injectors to get it going-could an injector still need bleeding? Would it run on less than four?
Also, I went through the timing process in the manual (pump is rebuilt.resealed), but am wondering if the pump timing alignment could be slightly off, but run none the less. Is it common to rotate the pump slightly to fine tune timing?
Or am I barking up the wrong tree and its just a normal break in process?
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Old 08-05-2020, 04:30   #2
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Re: perkins 4-108 Break In after Rebuild

If it does not have a load that might be why. Bob
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Old 08-05-2020, 05:29   #3
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Re: perkins 4-108 Break In after Rebuild

We have rebuilt over 200 Perkins 4.108's in the last 15 years. I have a two page instruction describing "Break In " procedures. PM your email & I will send you a copy.
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Old 08-05-2020, 06:26   #4
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Re: perkins 4-108 Break In after Rebuild

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Originally Posted by oldcal46skipper View Post
We have rebuilt over 200 Perkins 4.108's in the last 15 years. I have a two page instruction describing "Break In " procedures. PM your email & I will send you a copy.
Sounds interesting - any chance you can post something for posterity?

I used to be a delivery skipper and delivered many new Trawler Yachts (mostly Nordhavns). At the time, Lugger was still building and a very popular engine, though JD was also popular (and the base engine of the Lugger 6cyl ~300hp - I forget the model). I was told the break-in oil had a mild abrasive in it to help the rings seat. As a result, oil was recommended to be changed promptly at 100 hours. I changed oil on a couple engines at sea mid-delivery with wing engine running.

Peter
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Old 08-05-2020, 11:45   #5
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Re: perkins 4-108 Break In after Rebuild

Following......
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Old 08-05-2020, 12:42   #6
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Re: perkins 4-108 Break In after Rebuild

Personally I don’t like revving an engine with no load on it. An engine is supposed to actually do “work”. When you are revving it with no load, pressure and heat are not converted to work, and it changes the heat balance of the engine and it’s component parts.

Now, if it is called for in the Service & Operating Manuals, that is a different thing.

Blue Smoke: burning lube oil, rings/valve guides/just rebuilt.
White Smoke: running too lean, (make sure it isn’t water vapor)
Black Smoke: running too rich, Incomplete combustion, engine overloaded, bad injector

Not leaking lube oil? With a British engine that is considered a cause for concern

Keep us informed as to your progress, Good Luck!
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Old 08-05-2020, 13:07   #7
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Re: perkins 4-108 Break In after Rebuild

Buen dia,me dedico a la inyeccion diesel por eso puedo aconsejarlo.
Si su motor echa humo(sobre todo cuando esta frio)en ralenti es muy posible que este atrasado.Seguramente esta un poco mas silencioso que lo normal.
Ud puede girar la bomba inyectora aflojando los 3 tornillos que la sujetan sin temor,nada se va a romper.En el cuerpo de la bomba inyectora hay una chapa de aluminio con una flecha que indica la direccion de giro,usted gire el cuerpo en el sentido CONTRARIO a la flecha y pongalo en marcha a ver si nota diferencias.
El perkins tiene tambien otra forma de corregir la puesta a punto:
En el frente del motor(la distribucion) hay una tapa de chapa o una bomba de agua justo enfrente de la bomba inyectora .quitela y se encontrara con el engranaje que acciona la bomba inyectora.En el centro de este engranaje hay 3 tornillos que permiten mover el centro del engranaje (incluso tiene una marca para tomar como referencia)afloje los 3 tornillos y mueva el centro del engranaje PERO EN ESTE CASO MUEVALO EN EL SENTIDO DE GIRO QUE INDICA LA CHAPITA DE LA BOMBA) y pruebe el motor.
Le dejo mi correo si tiene mas dudas ,estoy en la patagonia argentina
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Good morning, I am dedicated to diesel injection so I can advise you.
If your engine is smoking (especially when it is cold) at idle it is very possible that it is running late, it is probably a little quieter than normal.
You can rotate the injection pump by loosening the 3 screws that hold it without fear, nothing will break. In the body of the injection pump there is an aluminum sheet with an arrow that indicates the direction of rotation, you rotate the body in the OPPOSITE direction to the arrow and start it to see if you notice differences.
The perkins also has another way to correct the set-up:
In the front of the engine (the distribution) there is a sheet metal cover or a water pump just in front of the injector pump. It will meet the gear that drives the injector pump. In the center of this gear there are 3 screws that allow moving the center of the gear (it even has a mark to take as a reference) loosen the 3 screws and move the center of the gear BUT IN THIS CASE MOVE IT IN THE DIRECTION OF TURN INDICATED BY THE PUMP FLAP) and test the motor.
I leave you my email if you have further questions, I am in Argentine Patagonia
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Old 08-05-2020, 13:40   #8
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Re: perkins 4-108 Break In after Rebuild

I bought my 4-108 in a box as a total loss from oil pressure failure and put it together, after having the crank inspected by the best machine shop in our area. No damage found. Put it all together and found after adjusting the valves that the timing would strongly affect engine sound and performance..forward and it would have the loud diesel sound of clatter and retarded it would smooth out and sound almost like a gas engine and run very quietly but it would then begin to smoke. So the task was to advance enough to burn clean without the harsh clatter..

Ive got over 600 hours on it now without a problem other than a bit of drip from that darned front oil seal
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Old 08-05-2020, 13:51   #9
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Re: perkins 4-108 Break In after Rebuild

Rebuild is somewhat a nebulous term, I'd us good oil and change well before the normal interval. Maybe 1/4th. I think you will be fine.
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Old 08-05-2020, 13:53   #10
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Re: perkins 4-108 Break In after Rebuild

Run it under load at various rpms.
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Old 08-05-2020, 17:13   #11
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Re: perkins 4-108 Break In after Rebuild

So a little further diagnosis. ran it up today, various rpms. Engine seems to smoke less as it warms up. I loosened an injector at a time while running and confirm all injectors are firing. The smoke is dark-not really blue, definitely not white. Since the injectors seem good, I worked backwards and found a "olive" that is not seating securely on the common return line that runs across the top of all four injectors. In that casagain, this just might be normal breakin stuff-oil pressure is 50 pounds. Also, head has not been retorgued yet, so could be a leak there.
How do I put a load on an engine that is running on a bench??
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Old 08-05-2020, 17:30   #12
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Re: perkins 4-108 Break In after Rebuild

Quote:
Originally Posted by jpendoley View Post
..........
How do I put a load on an engine that is running on a bench??
I don't think you can but I would very happy to be proved wrong!!!

I have been trying to work out a reasonably cheap DIY solution for several years without any resolution. Maybe there are smarter people out there who know how to do it - without access to seriously expensive bench dyno.
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Old 08-05-2020, 17:44   #13
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Re: perkins 4-108 Break In after Rebuild

We use what we call a "Miss a sippi Dynamometer" that is a piece of 2" X 4" wood that we place under the output shaft coupling and lift against the coupling until it ignites.
That is an indication that the gear is not slipping.
When the wood starts to burn, that is an indication the gearbox is not slipping.
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Old 08-05-2020, 17:51   #14
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Re: perkins 4-108 Break In after Rebuild

Put it in the boat and run it hard to seat the rings, if the timing is retarded it won’t make good power and will be smoky, but will be quiet, but it won’t hurt anything, just won’t make good power.
If too advanced it will rattle like a cold motor even when hot and too advanced can cause damage.
However having just been rebuilt smoking is sort of normal as the rings haven’t yet seated, and they don’t seat until it’s put under a load as then the cylinder pressure is higher, strong load results in very high cylinder pressure, this blows the rings out to the cylinder walls and that makes the seat well.
Way back when and even to this day Aircraft engines used to be run in on Non detergent oil,for the life of me I can’t imagine why, I wouldn’t use non detergent oil, but would do my first oil change very soon, the reason is, is because any metal that is worn off is come so very soon and you don’t want that wear metal staying in the oil, so first change 5 hours max.
Now it won’t kill it if you don’t, but believe it’s best to.

You did have the injectors overhauled didn’t you? If not then that could very well be the cause of smoking.
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Old 08-05-2020, 18:20   #15
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Re: perkins 4-108 Break In after Rebuild

[QUOTE=a64pilot
Way back when and even to this day Aircraft engines used to be run in on Non detergent oil,for the life of me I can’t imagine why, /QUOTE]

Because there are anti friction additives in compounded oils. With the RMS finish required for aircraft cylinder walls, you need some wear to break them in.
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