Construction and other equipment - AC 7000 engine cranckshaft rotation

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AC 7000 engine cranckshaft rotation

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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=30621
Printed Date: 05 Aug 2025 at 1:30pm
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Topic: AC 7000 engine cranckshaft rotation

Posted By: superchief
Subject: AC 7000 engine cranckshaft rotation
Date Posted: 12 May 2011 at 7:17am

Crankshaft rotation on the 7000 series engine. Book states: 'when viewed from fan end, the rotation is clockwise". My HD6G is positive ground, and when hooking up engine in preparation for test prior to installation with a positive ground, crankshaft rotates CCW when viewed from fan end. When hooked up with negative ground from test batteries, crankshaft rotates CW when viewed from fan end.

My 6000 series engine siezed up, and I am trying to prevent a recurrence with this replacement. Thanks, Superchief

Replies:

Posted By: Dnoym N. S. Can.
Date Posted: 12 May 2011 at 7:28am

whether negative ground or positive ground,
crankshaft rotates will stay the same starter
don`t care .to change rotates you have to
rewire the inside of the starter
and the drive has a one way clutch
can only turn the engine one way
HTH
B:-) Dnoym

Posted By: Butch(OH)
Date Posted: 12 May 2011 at 8:57am

Standard engine rotation for the world is clockwise when viewed from the front but most every mfg built anti-clockwise rotating engines for bastard applications. I have never seen a starter that would reverse when you reverse the leads, is that one of the military 7000s that are listed for sale? Right or wrong roatation engine for your application can be determained by spining it over the correct direction for the tractor and putting your hand over the exhaust outlet, and praying that it is pushing air out,, not sucking in

Posted By: wfmurray
Date Posted: 12 May 2011 at 12:01pm

Rotation is determined from the front or the fan end of engine. All other parts are determined from driver's seat.

Posted By: Chris/CT
Date Posted: 12 May 2011 at 2:53pm

I had a counter-rotating small block chev [350 ci] in a ChrisCraft cruiser. Now for the life of me I cannot remember, but I want to say the camshaft/crank gear's were set-up for this rotation, Distributer gear also, maybe I'm just not able to remember 20 years ago and everything I just said is wrong? My friend and I built the engine, [283 ci] was shot. One might think the engine could have been standard rotation and "change" made in transmission, but pretty sure that was not the case. It was "Left hand" rotation if I remember correct.

Posted By: michale34
Date Posted: 12 May 2011 at 4:41pm

I know one timeI had a ac hd6 with a 6000 engine and went to start it and it backfired and was running backwards exhaust smoke was coming out the air cleaner .

Posted By: superchief
Date Posted: 12 May 2011 at 4:45pm

Butch, Yes this is a 7000 engine military surplus, appears to be in good shape. Unit was used to power military generators 50-60KW which would bge similar to what we used in service. ( the cost wasn't bad, but the shipping was terrible).

I will pull further cranking checks in the morning. Checking the exhaust is a good idea.

This starter will change polarity when the leads are reversed. Test arrangement is two HD 12vt. batteries in series and connected directly to the starter poles.

As to damage on my 6000 engine, when we finally got the oil pan off we found a lot ( big bunch) of real thin metal shavings, perhaps a sleeve . When the engine shut down, there was no smoke, rattle, etc., it just died never to restart or crank, locked up solid. Will know more when we get the head off and rods and pist ons removed.

Posted By: superchief
Date Posted: 12 May 2011 at 4:53pm

Hi, thanks for the information, I will work to get this engine cranking and running in the right rotation, and hopefully prevent any further mishaps or frozen engines. Superchief

Posted By: Dnoym N. S. Can.
Date Posted: 12 May 2011 at 8:02pm

[QUOTE=superchief]

This starter will change polarity when the leads are reversed.
Test arrangement is two HD 12vt. batteries in series and
connected directly to the starter poles.

two 12 volt batteries in series that would run 24 volt system??

What is an automotive Starter Motor? It is a Series Motor
(for the greatest starting torque. ).
And what do you see, looking at the outside of the starter
motor? First, you only get to see ONE heavy terminal; the
other leads are already attached internally (one is connected
to GND), right? If you reversed the polarity, the direction
will not change because you just changed polarity for both
the Armature and the Field wires.

PERMANENT MAGNET MOTORS: All the rules just changed
(sort of). We use rare earth and other very efficient materials
to make great magnets, today. (They didn't have that for
serious motors in the old days; only little motors with weak magnets.)
Since permanent magnetism is constantly produced
(not wired), if you change the polarity (motor leads),
the motor will run in reverse!

All the NEW STARTER MOTORS USE PERMANENT MAGNETS!!!

This only started around 1993 or so. That's why

the starters got a lot smaller in size; the magnets

are a lot smaller than the field windings were,

so they used some of the space-savings to

install gear reduction, for yet more torque.

Since permanent magnetism is constantly produced

(not wired), if you change the polarity (motor leads),

the motor will run in reverse!

but the drive has a one way clutch and
can only turn the engine one way

the started would only spins not turn over

some of the thing they have to do to reverse

engine rotation is cam grown the other way and the

oil pump is backward as well.they done this on boat`s

let us know how you make out

B:-) Dnoym

Posted By: superchief
Date Posted: 12 May 2011 at 9:44pm

Hi, Thanks Dnoym, My HD6G is a 24vt system and uses a Dyer Enclosed Shift Type Starter with Over-running clutch. The starter is very heavy and is about 22 inches long from the nose to the rear of the starter. There is a ground lug on the end of the starter and one lug on side of the starter to which the solenoid is connected too. The other large lug on the solenoid has a lead connected to the ground lug on the end of the starter to which the hy-lift frame is connected to the starter. Thanks for your assistance. Superchief

Posted By: HD6 Merv
Date Posted: 13 May 2011 at 2:51am

Hi Chief

One little point; your probably aware of it anyway; but connect a oil pressure gauge up before you start it; jusy to make sure bloods getting to where it needs to.

Good luck and cheers

Merv

Posted By: superchief
Date Posted: 13 May 2011 at 2:16pm

Hi Merv, The blood is flowing on the CW cranking at 35-40psi. don't have a way to pressurize incoming fuel. This engine has a Stanadyne Injection pump and no lift pump, fuel by gravity flow will not achieve the 5-10psi required. Looks like in order to hear the engine run, we will need to use a electric fuel pump for bleeding the injectors and running the engine in the cradle. Will try and keep you informed. A note of interest; this engine is painted desert tan instead of Army OD. maybe it was in Iraq ? Thanks, Superchief

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