Construction and other equipment - 3-71 Detroit Mystery

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3-71 Detroit Mystery

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Construction and other equipment
Forum Description: everything else with orange (or yellow) paint
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=33386
Printed Date: 03 May 2025 at 8:13am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: 3-71 Detroit Mystery

Posted By: needsomeparts
Subject: 3-71 Detroit Mystery
Date Posted: 05 Jul 2011 at 9:42pm

Just purchased a HD-7 with the 371 Detroit. The previous owner stated it run fine two years ago when parked. When I got it home (I never tried to start it) I started doing the services and dropped the engine oil and it was full of gear teeth. I pulled the pan and found over a hundred pieces of teeth most are over .50" long and some are 1.5 inches. I inspected the crank grear and there is not even a scratch on one of the teeth. I pulled the small round covers on the rear of the engine and inspected the idler gear, the cam gear, the balance shaft gear and the blower drive gear, not so much as a single chipped tooth. Where did all the gear teeth come from?

Replies:

Posted By: Coke-in-MN
Date Posted: 05 Jul 2011 at 9:54pm

how about the gears on the blower lobes themselves .

One 2-71 in a HD5 I bought was ran when parked and when I went to start it it was locked , ended up blower lobe was broken from getting water into blower,( drain hole was plugged) and broken gear teeth from the locked lobe

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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."

Posted By: q4016lanz
Date Posted: 05 Jul 2011 at 10:17pm

You will have to check every tooth in the machine turn it over with a spanner on the harmonic balancer nut by hand first take the injectors out. some one my have repair a gear in it and and left the broken peices in the sump

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15 allis chalmers tractors

9 lanz bulldog tractors

2 water cooled deutz

9 john deeres tractors

14 Aus made orange chamberlains

I spent most of my money on old tractors I wasted the rest

Posted By: needsomeparts
Date Posted: 05 Jul 2011 at 10:29pm

I have not inspected the blower gears yet. Are the oil return to crankcase holes big enought to let all those big chunks through without plugging? I pulled the intake tube to the blower and watched the lobes turn all the way over as I turned the engine over by hand. How much lash should be felt in the lobes if turned by hand? Every tooth on the rear on the motor has been accounted for.

Posted By: Coke-in-MN
Date Posted: 05 Jul 2011 at 10:34pm

there is very little lash in the blower lobes as they are extreme close tolerance and lobes are timed to each other so they do not clash.

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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."

Posted By: needsomeparts
Date Posted: 05 Jul 2011 at 10:42pm

Yea thats what I thought, anyway in there with a bore scope or do I have to pull the blower to inspect those two gears?

Posted By: gemdozer
Date Posted: 06 Jul 2011 at 5:01am

I dismantled 3 motors DETROIT 371 if sometime I can help.

Posted By: needsomeparts
Date Posted: 06 Jul 2011 at 10:13pm

Well I didnt find any teeth broken in the blower so I put it all back togather, changed oil and filter put in a new fuel filter and fuel and it started right up. I cannot believe someone would replace just the gear that shelled out and not even bother to check the pan. Wow. It does seem to surge a bit but if I hold the rod that connects the injectors to the govenor it smooths right out. Is my gov just gummed up from sitting??? I do need a starter solenoid and I think my steering clutches might be froze but and least my motor is good.

Posted By: Coke-in-MN
Date Posted: 07 Jul 2011 at 8:44am

At low RPM they will surge if everything is not set right as the governor brings idle down and then catches up.

Depending on the starter , solonoid is not a big issue or if the older type you can service the unit yourself by cleaning the internal contacts within the cap.

Posted By: wfmurray
Date Posted: 07 Jul 2011 at 1:24pm

I hear those engines will idle but they let them surge so they want get to cold . Might be just old wives tale.

Posted By: Tad Wicks
Date Posted: 07 Jul 2011 at 1:41pm

It will smooth out when it warms up, if not, you might have to run the racks and get everything in sync. The starter should engage by foot . Tad

Posted By: Coke-in-MN
Date Posted: 07 Jul 2011 at 2:33pm

Might be like mine I took the starter off and updated to late style starter with solonoid. As I changed to alternator it was easy to put on key switch and change out starter with the M42 style with adjustable front cone. Would have cost the same to rebuild one of mine as it did to just exchange for the late starter.

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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."

Posted By: DMiller
Date Posted: 08 Jul 2011 at 5:08pm

There is a idle 'buffer' adjustment on the governor setting adjusters,(smaller screw in the governor adjusting plunger) most times the spring on the adjustment screw gets beaten down and can no longer do its job. As a older truck/equipment mechanic I can attest to leaving scraps in the oil pan as components failed providing there were large enough to not get into the oil pump system. Gear remains as a Detroit blower died, push rod chunks and end caps on the old Cummins engines was a normal when we tore engines down for full overhauls.

Flush as much as possible, quickly out the drain hole with fuel and old oil then reassemble to run a while longer.

Posted By: beeman
Date Posted: 10 Jul 2011 at 4:56pm

I once dropped the little drive shaft that runs the distributor on a ford dump truck v8 gas engine. Heard it fall down into the pan...!!! I just could not let it stay there and dropped the pan....found 3 of the shafts in there !!!! Parts house guy told me they sold them all the time.......

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1949 B 3930 Ford- Have owned other Orange ,green,red,yellow,dark green tractors and equipment.