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Vintage Diesel and Oil Engines Fairbanks Morse, Lister, Petter, Witte and other pump injected Diesel oil engines.

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GM 3-71 Injectors


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  #1  
Old 11-11-2018, 11:34:31 AM
glennh glennh is offline
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Default GM 3-71 Injectors

Hello All.

I am new on this board, but I have been fascinated with making old things run for a long time, and I have found a lot of useful information here.

My question is about a new engine that I acquired this week. It is a 3-71 GM diesel that is (hopefully) destined to power my dad's Belsaw sawmill.

The 3-71 was removed from a crane about 5 years ago, and is set up on a home made frame with a Twindisc PTO. The engine itself has a thick layer of yellow paint on top, with orange underneath, and a spot of Olive Drab in places. Based on the paint and the intake/exhaust setup, I have decided that it is most likely from an Allis Chalmers HD7.

My question though, is about the injectors. Everything about the engine appears to be ready to run after a good flushing and cleaning, except the injectors. All three are stuck.

I have removed the injectors and let them soak in diesel for a few days. A gentle tapping on the plunger didn't do them any good, so I opened one up. Repeated soaking, spraying and tapping has failed to loosen the plunger on the one I took apart, so I have decided to look for new (rebuilt) injectors. The problem is finding the right ones. The injectors have no letter, only "GM Diesel Equipment 70" The in/out ports are not offset as on other Detroits I have worked on.

Can anyone direct me to a good reference for old GM injectors so that I can cross these injectors to something more recent?

Thanks for any help.

Glenn
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Old 11-11-2018, 11:53:58 AM
Norm W Norm W is offline
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Default Re: GM 3-71 injectors

It sounds as though you have a HV70 injector. If you wanted to you could replace them with HN60 injectors. You probably have a two valve head, which takes the old High Valve injector body. The "N" type has a better spray pattern hence the H (high valve body) N (N type spray pattern) label.
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Old 11-11-2018, 01:47:06 PM
K-Tron K-Tron is offline
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Default Re: GM 3-71 injectors

If the only number on the injector is 70, the engine you are working on is very old. The 60, 70, 80 and 90 injectors were 1937-~1946. Your engine will run much better with a HV (High Valve) type injector. HV7 would be the equivalent of the old GM 70. The HV injectors have the same body as the old number series GM injectors. You will not be able to run offset body (current) injectors in your engine. I may be interested in your old original injectors if you want to part with them.

Chris
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Old 11-11-2018, 01:54:18 PM
glennh glennh is offline
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Default Re: GM 3-71 injectors

Thanks Norm. I have read about the HN injector elsewhere. My biggest concern is the orientation of the fuel ports. I have found photos of HV injectors that have the offset ports. How can I be sure that I'm getting something that will work? Pictures make everything easier so here they are.
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Old 11-11-2018, 01:58:20 PM
glennh glennh is offline
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Default

Name:  hv7.jpg
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Size:  1.4 KBThis is a photo from Ebay. Hope it's big enough to see. This appears to be an HV7 with the offset body.

Chris,

The Allis HD7 used the 3-71 in the 1940s, so that would match my suspicions.

This photo is better.
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  #6  
Old 11-12-2018, 02:26:31 AM
The Diesel Doctor The Diesel Doctor is offline
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Default Re: GM 3-71 injectors

Quote:
Originally Posted by glennh View Post
Hello All.

I am new on this board, but I have been fascinated with making old things run for a long time, and I have found a lot of useful information here.

My question is about a new engine that I acquired this week. It is a 3-71 GM diesel that is (hopefully) destined to power my dad's Belsaw sawmill.

The 3-71 was removed from a crane about 5 years ago, and is set up on a home made frame with a Twindisc PTO. The engine itself has a thick layer of yellow paint on top, with orange underneath, and a spot of Olive Drab in places. Based on the paint and the intake/exhaust setup, I have decided that it is most likely from an Allis Chalmers HD7.

My question though, is about the injectors. Everything about the engine appears to be ready to run after a good flushing and cleaning, except the injectors. All three are stuck.

I have removed the injectors and let them soak in diesel for a few days. A gentle tapping on the plunger didn't do them any good, so I opened one up. Repeated soaking, spraying and tapping has failed to loosen the plunger on the one I took apart, so I have decided to look for new (rebuilt) injectors. The problem is finding the right ones. The injectors have no letter, only "GM Diesel Equipment 70" The in/out ports are not offset as on other Detroits I have worked on.

Can anyone direct me to a good reference for old GM injectors so that I can cross these injectors to something more recent?

Thanks for any help.

Glenn
You can get a better price if you have a acceptable core when you buy a rebuilt injector. soak your injector in WD40 for a few days and then tap the control rack back in forth with a small hammer. If it has an undamaged tip and a free rack its a good core. I get my injectors from PC Industries in Afton Wyoming. AL
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Old 11-12-2018, 09:40:45 AM
miltruck miltruck is offline
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Default Re: GM 3-71 injectors

I agree with all of the above, but would recommend that you down size the injectors to the smallest ones suitable for the 3-71. Not sure which Bel-Saw mill you have, but my father sawed hundreds of logs with a 42/48" mill using a Long 460 tractor to power the saw via a pto setup. Tractor is only 45 pto hp and would saw 20" white pine like it was balsa wood. Red oak was a little tougher but still worked fine if you adjusted the feed rate.

Again, not knowing what setup you have, you may have to come up with a step down pulley system as my father's mill ran at about 550-650 rpm and clockwise when viewed from the rear end of the tractor. The Detroit won't like to run under load below 1,200 rpm under load but may work using a 2:1 step down.
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Old 11-12-2018, 11:00:38 AM
glennh glennh is offline
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Default Re: GM 3-71 injectors

Belsaw advertised that the mill could be run with a 30 HP engine and the power feedworks takes another 25HP.

We have converted to a larger mandrel and a hydraulic drive for the feedworks, so we're losing some power there. We also have to run it through a belt reduction as you said, so that eats up some power. It's currently under power with a chevy 250 gas engine running through an SM465 4 speed running in reverse. This powers a main shaft that runs the hydraulic pump and belt drives to the mandrel. This unit runs well and is quiet, but we can't get a governor to keep up with the mill.

Given all of the advice above, I think that I want to go with the HN60 injectors, but I'm still not clear on the High Valve designation. As long as the fuel ports are straight across and not offset, the injector should work?

Thanks for all of the help. This is a great forum.
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Old 11-12-2018, 11:58:14 AM
Norm W Norm W is offline
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Default Re: GM 3-71 injectors

The offset fuel ports are for the 4valve heads. You have an engine with a 2valve head. That takes the type with the side by side ports. The 71 series engines put out about 35hp per cylinder at full power. The smaller injectors will produce less power, but run cleaner, because there will be more "Air" to fuel when running. "Rolling Coal" just wastes fuel. I dropped from HV70 to HN55 and eliminated all the smoke on acceleration in my 671. It dropped the HP from 238 to about 185, but the mileage went from 6.5 to 10.5. I can still cruse at 65mph.
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Old 11-12-2018, 12:29:37 PM
K-Tron K-Tron is offline
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Default Re: GM 3-71 injectors

If you cannot find new or rebuilt injectors, a good 2 cycle Detroit diesel shop can put the innards of an offset body "N" injector into your 70 straight body injectors. I know several folks that have done so. It looks original under the valve cover and runs without the constant gray/black haze the original 70 injectors had while running. I doubt any shop will give you any money for those old injector cores, they are not serviceable anymore. Leid Diesel in PA likely has a matching set of rebuilt straight body injectors on the shelf for you. They would love to hear about your old diesel & your project.

Chris
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Old 11-12-2018, 12:36:38 PM
The Diesel Doctor The Diesel Doctor is offline
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Default Re: GM 3-71 injectors

Your 70 and HV injector pop at 500 PSI The HN`s pop at 3000 PSI. Better atomization and a clean exhaust. AL
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Old 11-12-2018, 12:58:25 PM
glennh glennh is offline
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Default Re: GM 3-71 Injectors

Thanks for all the feedback. I'll check the suggested sources and let everyone know when it's up and running. I should have time to get the oil changed and the fuel system flushed while I wait for injectors. Already got it cranking with the starter (no injectors), and it pumped decent looking oil out the pressure gage line.
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Old 11-12-2018, 02:06:46 PM
glennh glennh is offline
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Default Re: GM 3-71 Injectors

So, one more quick question before I buy injectors. I pulled the air intake to see what kind of condition the blower is in and this is what I found.Click image for larger version

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I assume that some of this oil is coming from the air filter, as the whole tube from the filter to the blower is coated with oil, but some of it must be coming from the blower, right? I also see several significant gouges in the lobe seals. Is this engine going to be worth putting money into, or should I find a newer 3-71 or 4-71?
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Old 11-12-2018, 03:14:33 PM
Mark Schneider Mark Schneider is offline
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Default Re: GM 3-71 Injectors

I rebuilt an ancient 6-71 crusher engine awhile back and the view in the blower box was very similar. The edges of the box look gritty which more than likely means the fine sand got pulled through the oil bath air cleaner. Your next move should be to remove the oval air box covers and do a visual on the innards. If there is a build up of oil and fine sand (resembling asphalt) on the bottom of the air box the liners and pistons will be toast. As you turn the engine over you will be able to see the compression rings go by the ports. If the rings appear to be sloppy in the grooves an overhaul will be needed.

The crusher engine I did had dual oil bath air filters and the bottom of the air box had a thick layer of that petrified oil/sand mix. I chiseled and pressure washed for hours trying to get that stuff out. Needless to say when I finished the rebuild the first thing I did was toss the original oil bath air filters in the junkpile and mounted a big paper element filter assembly off of a combine.
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Old 11-12-2018, 06:13:26 PM
Anthony60 Anthony60 is offline
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Default Re: GM 3-71 Injectors

Greetings Glen.
Looks like you have lots of good help here! Just putting my 2 cents worth, with the HV injectors, they have a more likelyhood of light smoke hazing. Back in the day I rebuilt 100's of inline 71's for the oilfields, 6-71's we kept them 2 valve heads(2 valve heads rarely dropped valves like the 4 valve heads) we would build them up with 4 valve cylinder kits and run offset N injectors they ran strong and clean...
I would recommend running N60's with an injector timing height of 1.460, this will run nice and clean. But with the offset N injectors you will need to replace the injector hold down clamps and fuel jumper lines as well.
I have manuals I can look up any other info you might have.

Quote:
Originally Posted by glennh View Post
So, one more quick question before I buy injectors. I pulled the air intake to see what kind of condition the blower is in and this is what I found.Attachment 322733

Attachment 322734

I assume that some of this oil is coming from the air filter, as the whole tube from the filter to the blower is coated with oil, but some of it must be coming from the blower, right? I also see several significant gouges in the lobe seals. Is this engine going to be worth putting money into, or should I find a newer 3-71 or 4-71?
Blower Looks pretty normal for a high hour engine
The 'Grit' in the air box is mostly oily carbon and not dirt (the Joy's of a 2 stroke ported diesel). As long as the blower turns free without dragging sounds it still is runable. What you don't want to see a a completely oil washed set of rotors, that would mean blower seals, piston rings or piston pin retainers leaking. Keep in mind that they aren't called Driptroits for nuthing�� they are always going to slobber some oil out the drain tubes.
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Old 11-12-2018, 09:26:51 PM
The Diesel Doctor The Diesel Doctor is offline
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Default Re: GM 3-71 Injectors

What are the model and S/N of your 3-71? From the looks of the oil bath air cleaner, starter, generator, and oil filters i would guess the middle 40s. The off set injector will not fit in the two valve head because of interference with the valve springs. I agree with Anthony 60 on the blower. With the battery disconnected, you can push on the blower rotors and they should move slightly and spring back. When blower lobes touch you know it and their will be polished surfaces on them. AL
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Old 11-12-2018, 09:50:41 PM
glennh glennh is offline
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Default Re: GM 3-71 Injectors

Model 371RC-6

Serial 3716568
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Old 11-12-2018, 11:19:44 PM
The Diesel Doctor The Diesel Doctor is offline
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Default Re: GM 3-71 Injectors

According to your S/N it was the [7586] 3-71 built. My data book goer back to 1972 and shows the first 3-71 to be built in 1972 was SN 79536 and starting in 1993 102396 had been made. KTRON might be able to find more info on this and enlighten us. AL

Getting old, meant to say your engine was the 6568 3-71 to be built.
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Old 11-13-2018, 04:54:01 PM
Anthony60 Anthony60 is offline
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Default Re: GM 3-71 Injectors

Quote:
Originally Posted by The Diesel Doctor View Post
What are the model and S/N of your 3-71? From the looks of the oil bath air cleaner, starter, generator, and oil filters i would guess the middle 40s. The off set injector will not fit in the two valve head because of interference with the valve springs. I agree with Anthony 60 on the blower. With the battery disconnected, you can push on the blower rotors and they should move slightly and spring back. When blower lobes touch you know it and their will be polished surfaces on them.
AL
DR DIESEL, Its been a long time but I do remember running N65 injectors in those old 6-71s, I may be wrong
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Old 11-13-2018, 09:41:06 PM
The Diesel Doctor The Diesel Doctor is offline
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Default Re: GM 3-71 Injectors

Anthony60, If your inline 6-71 had a four valve head a N65 would fit in the injector tube. If the engine has a two valve head it wouldn`t Before HN injectors were available i took HV injector bodies and machined and lapped them to the dimensions of my N 60 bodies. Transferred the N parts to my straight bodies They were in in a 4-71 and they worked. AL
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