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Generators & Motors General Discussion Antique Generators, Light Plants and Old Electric Motors: Questions and answers about restoring and showing old power generation systems.

Generators & Motors General Discussion

3-71 GM Diesel GenSet


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  #1  
Old 06-28-2006, 10:09 AM
Roger Boardman Roger Boardman is offline
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Default 3-71 GM Diesel GenSet

Was given a GM genset under the condition that I get it out of the Microwave tower site. This was done and a garage built around it when I got it home. I removed the muffler from the outside of the block building that I removed the set from. The muffler is about 14" in dia. and 40" long, how close to truss and roof sheathing can this be? I have no experience with this engine or exhaust and do not wish to set the house ablaze. Thanks. Roger
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Old 06-28-2006, 05:46 PM
mylesdw mylesdw is offline
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Default Re: 3-71 GM Diesel GenSet

Not sure how relevant this is but my experience with a National 2 cylinder diesel in a boat is that the exhaust does not run very hot; you can easily touch the exhaust where it comes off the manifold and you can use the silencer to warm your hands on!
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Old 06-28-2006, 06:48 PM
Jim Rankin Jim Rankin is offline
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Default Re: 3-71 GM Diesel GenSet

How hot it gets will depend on the load on the generator. Be safe and allow a couple feet from anything combustable, but be aware that radiant heating can get things hot enough to burn too. My neighbor had to add some sheetmetal shielding on the ceiling of the shed he built to house an 85kW Onan.
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Old 06-29-2006, 10:16 AM
Ray Griffiths Ray Griffiths is offline
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Default Re: 3-71 GM Diesel GenSet

Hi Jim
I have a statonary 3-71 engine that is also driving a 12 kw gen head. While the DD definitely moves more air than a 4 cycle engine, (about 2x as much) the exhaust gets plenty hot. You won't be laying your hand on it. I'd try to keep at least 18" between it and anything flammable. There is shielding and even piping made for wood stoves that could be used to reduce this though.

My engine is old (made in 1946) and came with a straight pipe. I put on a muffler, but am still trying to figure out a way to quiet it more. The muffler I have is about 10" in diameter, and about 24" long. How loud is your engine with the stock muffler? I tried putting the end of the exhaust pipe in a water tank, but it's moving so much air it blew water all over the place. I'm thinking of filling the tank with 1" gravel now. Even if the exhaust is quieted, the rest of the engine still makes a lot of noise. Hope you don't have neighbors that are very close.
Ray
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Old 06-29-2006, 10:47 AM
Roger Boardman Roger Boardman is offline
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Default Re: 3-71 GM Diesel GenSet

I have only ran the set twice, last night I ran it for about 45min. and the stack never got so hot that I could not touch it, however it was not loaded. The first time there was no muffler on it and it was painful. After I ran the stack up into the trusses and put the muffler up there and the stack through the peak I was able to determine that the gasket on the exhaust manifold is leaking on the #2 cylinder and so there is a lot of report still. As you say the engine is just noisey even with the absence of exhaust note, and it is moving a lot of air. This is a 3 phase set, with 1532hrs. on the clock, there is a hand written note in the control cabinet stating, lube oil and filter changed 10-31-1957 @ 257hrs. Anyone have any good and cheap ideas on putting a large load on this machine??? It really needs a workout. Thanks Roger
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Old 06-29-2006, 12:08 PM
Ray Griffiths Ray Griffiths is offline
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Default Re: 3-71 GM Diesel GenSet

Interesting, I haven't really loaded mine either, it is for a sawmill, still under construction. The 12 kw gen head is mounted to the side and runs off a pulley on an outboard shaft. I've used it for welding, but other 3-71's generators are rated about 45 kw or so, as I recall. I can't even tell it has any load from the generator. More questions, sorry.
Do you know the kw rating of yours? Is the engine 4 valve? Turbocharged or not? What rpm is the govenor set for?
Inquiring minds and all that.

When I've run mine for an hour or so, even under the light load of the generator, the exhaust has wavering heat coming off it, touching it with bare skin would be an instant burn. Mine is an old 2 valve, maybe the 4 valve moves enough more air to stay cooler? Just a guess. I don't know what to tell you about loading it, you could likely run your whole neighborhood off it.
Ray
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Old 06-29-2006, 01:52 PM
B.Sparks B.Sparks is offline
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Default Re: 3-71 GM Diesel GenSet

"my experience with a National 2 cylinder diesel in a boat is that the exhaust does not run very hot; you can easily touch the exhaust where it comes off the manifold and you can use the silencer to warm your hands on!"

The exhaust system on a marine engines is usually water cooled. The exhaust manifold has a water jacket. There is usually a fitting downstream of the exhaust manifold where spent cooling water is injected into the exhaust stream. As a result the exhaust manifold and plumbing stay (comparatively) cool during engine operation.

We have a 1958 vintage 75 kVA P&H Harnishfeger genset. The P&H engine is a 2 stroke unit similiar to a Detroit, but it is equipped with a conventional rotary injection pump. I can assure you that the exhaust gets quite hot, even under light load. At no load in cool weather it likes to wet-stack. Even though the engine operates at a mild 1800 rpm, this beast SCREAMS! Most of the noise is generated by the scavenging blower (or "supercharger.")
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Old 06-29-2006, 03:04 PM
Roger Boardman Roger Boardman is offline
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Default Re: 3-71 GM Diesel GenSet

Mine is a two valve head, had the rocker cover off to free up the injector rack, no turbo just the blower, it turns 1200rpm and is a 30kw unit so I assume it is a 6 pole head. It is nice to look at it as everything says it was made in the United States, all steel and iron and real copper. Roger
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Old 07-01-2006, 06:18 PM
K D Redd K D Redd is offline
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Default Re: 3-71 GM Diesel GenSet

To load you unit visit you local scrap yard and buy all the electric range elements you can find. It will take many to load a 30 KW generator. Also a local genset dealer may have a load bank that is mobile. You could pay them to load your genset for testing. I check with a local genset dealer about teasting a 100 KW set. The charged $75/hr 3 hour minimum.

Kent
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Old 07-01-2006, 08:03 PM
Ray Griffiths Ray Griffiths is offline
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Default Re: 3-71 GM Diesel GenSet

Roger, here is a webpage on insulating mufflers for diesel gensets. Look on page 14, I think?, middle of the pages.

http://www.bowerspower.com/pdfs/Inst...guidelines.pdf

My engine runs at 1800 rpm, which would make a difference in the heat generated, but even so, I'm surprised at how cool yours runs. Better safe than sorry though.
Good luck.
Ray
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Old 07-01-2006, 09:36 PM
Wayne 440 Wayne 440 is offline
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Default Re: 3-71 GM Diesel GenSet

Go to your local HVAC place and buy a couple of the old electric furnaces they have from wreck outs. They are almost an instant load bank, with a bit of creative wiring. A of 15kw units would let you see what your set is made of.
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Old 07-07-2008, 08:38 PM
russcomp russcomp is offline
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Default Re: 3-71 GM Diesel GenSet

Quote:
Originally Posted by Ray Griffiths View Post
Roger, here is a webpage on insulating mufflers for diesel gensets. Look on page 14, I think?, middle of the pages.

http://www.bowerspower.com/pdfs/Inst...guidelines.pdf

My engine runs at 1800 rpm, which would make a difference in the heat generated, but even so, I'm surprised at how cool yours runs. Better safe than sorry though.
Good luck.
Ray
interesting site any others ???
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Old 07-11-2008, 09:29 PM
K D Redd K D Redd is offline
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Default Re: 3-71 GM Diesel GenSet

Remember, With a DD engine a lot of the noize is the gear train that drive the blower and the blower. A muffler will not reduse this noize. There is a guy on the Yahoo DD forum that claims that a DD engine is the Most Efficent Way to turn diesel fuel into noize. They are NOT called Screaming Jimmy's for nothin !!!

Kent
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Old 07-11-2008, 09:48 PM
armandh armandh is offline
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Default Re: 3-71 GM Diesel GenSet

the real load test
I've posted pics of the 7200 watt kohlerK series powered homelight.

I hooked it up to the barn/tractor shed load and kept turning things on

the lights, the fans, the AC, open a hot water tap until the water heater came on the load.

it just kept getting louder
until the breakers opened then back to a quiet rumble
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