What should be the dwell be again?

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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Re: What should be the dwell be again?

Post by Joe Gopan » Tue Oct 25, 2016 11:00 am

Something else important to consider while servicing your distributor is to clamp a dial indicator to the base in order to check the total side play of the shaft at the cam. It should not be more than 0.005". (New Distributor is 0.001")
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Re: What should be the dwell be again?

Post by artificer » Tue Oct 25, 2016 12:36 pm

This topic started by simply asking what should the cam dwell be [for a typically standard WW2 Jeep] The answer is 41-42*.
Someone is trying to confuse us all.
Is anyone confused, because they should not be?

Diagnosis is the name of this game, finding if something is wrong & if there is nothing, why do any extra work unnecessarily?

Forget about all this ancient history US Army stuff being done to death, as it is irrelevant to what anyone can do with the simplest of inexpensive tools, without pulling distributor caps, leads, rotors & trying to check point gap with feelers inside the distributor.

This can be accomplished by using a simple multi-function auto multimeter like this.
Image
The cam dwell [& this indicates point gap] is checked in <1 minute by even the most inexperienced person capable of hooking up 2 leads as shown....the red to the coil lead & the black to a good ground & setting the gauge on dwell & running the engine
Image
If the dwell reading is correct & you are only checking, you need do nothing else except remove the 2 leads, then you are done.
If the dwell reading is too large the point gap is too small & if too low the point gap is too wide, you need to adjust while checking what caused this to occur. Most likely the point rubbing block was not lubed with high speed grease [a very small dab only on the cam].
If the dwell reading is inconsistent by a few degrees either way when the engine is revved this indicates there is wear/damage inside the distributor housing related to any of the following:
The cam/bushing/shaft the cam is mounted on. It means both the dwell & point gap is altering. This can only happen when the cam position is inconsistent

Rather than this flogging this dead horse any further, some may choose to read this detailed explanation
https://www.howacarworks.com/ignition-s ... well-angle
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Re: What should be the dwell be again?

Post by Jon » Tue Oct 25, 2016 10:28 pm

Personal attacks will not be tolerated......
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Re: What should be the dwell be again?

Post by artificer » Sun Oct 30, 2016 1:04 am

For the heck of it I checked TM 9-1825 section 64 fig B & IGC 4705 point dwell is shown as 42* not what has been indicated earlier & in a number of other threads.
It would appear that all WW2 Jeep distributors have the same dwell angle according to official TM publications & confirmed in both the Clinton Auto Repair Manual 27th Edition Page 800 @ 42* & Motors Auto Repair Manual 15th Edition Page 23 shown as 41*

This was found in another publication
IGNITION:
Breaker Gap—.020"
Cam Angle:
47° points closed [IGC- 4705] this may or may not be a mistake that has been carried through numerous threads as well
41° points closed [IAD-4008]

At the end of the day we are talking about using a dwell meter to check whether points need adjusting & the distributor internals are OK.
A steady reading of about 42* means point adjustment is fine as are the bushes, shaft etc.
Additionally if one adjusts to 0.020" point gap they can also check how accurate their feeler gauge skills are by checking with the dwell angle meter.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: What should be the dwell be again?

Post by Joe Gopan » Sun Oct 30, 2016 5:28 am

I'll stand behind the data I submitted from TM9-1825B dated 1952 on the IAD 4008 and IGC 4705 MB/GPW Distributors. with a dwell tolerance of +/- 3 Degrees and that the points are to be set at 0.020" regardless of what the Dwell checks out. And if the dwell is out of the specified tolerance, to repair or replace the cause such as worn shaft, worn cam, or bushing. Point setting of 0.020" is still the rule in the Auto-Lite TM.
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Re: What should be the dwell be again?

Post by artificer » Sun Oct 30, 2016 1:57 pm

John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: What should be the dwell be again?

Post by Joe Gopan » Mon Oct 31, 2016 5:47 am

And John, no need to avoid the actual Auto-Lite instructions in the TM for setting 0.020" point gap and not attempting to go by the cam dwell? No agenda on my behalf John, just the facts printed on the bottom of Page 230 of TM 9-1825B Nov 1952. Auto-Lite Electrical Equipment.
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Re: What should be the dwell be again?

Post by YLG80 » Wed Jun 24, 2020 1:26 am

The Dwell angle in an L-134 engine with the IAD-4008 distributor is 42 degrees (°) or the equivalent Dwell Time is 47 percent (%)
Read this :The truth about the distributor DWELL angle in a Jeep (L-134 and F-134)
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Re: What should be the dwell be again?

Post by Rob G. » Sun Nov 14, 2021 7:27 am

YLG80 and others,

After reading this thread again today .... it just occurred to me the simplicity of the 47% (Percent) reference!

42 degrees/90 degrees = 0.47 or 47%

It all makes perfect sense now!
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Re: What should be the dwell be again?

Post by McGyver » Sun Apr 17, 2022 6:05 pm

So when I set my points to the proper .020" gap, my dwell reads 48-50 degrees. This is with brand new points from Ron / Joe's Motor Pool. Would I be correct in assuming this means the cam lobes are most likely very worn? I can adjust the gap to get down to 42, but it makes my gap much wider than .020.
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Re: What should be the dwell be again?

Post by dinof » Sun Apr 17, 2022 6:17 pm

McGyver wrote:
Sun Apr 17, 2022 6:05 pm
So when I set my points to the proper .020" gap, my dwell reads 48-50 degrees. This is with brand new points from Ron / Joe's Motor Pool. Would I be correct in assuming this means the cam lobes are most likely very worn? I can adjust the gap to get down to 42, but it makes my gap much wider than .020.
My dwell meter reads 43.1 This is from making sure the .020 gap has been established. Same points you bought from Ron.
I know the points need to be at the right gap so, I'm ignoring my meter on this one. And in doing so, my jeep runs fine.
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Re: What should be the dwell be again?

Post by McGyver » Sun Apr 17, 2022 6:29 pm

dinof wrote:
Sun Apr 17, 2022 6:17 pm

My dwell meter reads 43.1 This is from making sure the .020 gap has been established. Same points you bought from Ron.
I know the points need to be at the right gap so, I'm ignoring my meter on this one. And in doing so, my jeep runs fine.
My jeeps seems to run fine both with both settings (i.e. if I just set with a .020 gap or if I adjust a wider gap to get 42 deg. reading on the dwell meter.) My understanding from reading this and a few other threads is the correct 42 deg. dwell would be easier on the coil. I am not however using an original coil, so I am not too sure how important this may be.
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Re: What should be the dwell be again?

Post by dinof » Sun Apr 17, 2022 6:44 pm

Use your feeler gauge and go with that. I trust the metal feeler gauge than a meter in this case.
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Re: What should be the dwell be again?

Post by Scoutpilot » Mon Apr 18, 2022 1:35 am

New points can be set with a blade feeler gauge. As they age you should consider the wire-type feeler due to the transfer and accretion of material from the fixed arm to the moving arm point. This leaves a point on the moving arm and a divot in the fixed arm.
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Re: What should be the dwell be again?

Post by YLG80 » Mon Apr 18, 2022 3:34 am

McGyver wrote:
Sun Apr 17, 2022 6:05 pm
So when I set my points to the proper .020" gap, my dwell reads 48-50 degrees. This is with brand new points from Ron / Joe's Motor Pool. Would I be correct in assuming this means the cam lobes are most likely very worn? I can adjust the gap to get down to 42, but it makes my gap much wider than .020.
Are you sure that your meter is displaying degrees and not % (duty cycle) ?
Your 48-50 reading is very close to 47% = 42 degrees.
Yves
Last edited by YLG80 on Mon Apr 18, 2022 8:51 am, edited 1 time in total.
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