Cam nut longer than cam step - what have I got?

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Model T Ford Forum: Forum 2018: Cam nut longer than cam step - what have I got?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Namdc3 on Saturday, December 15, 2018 - 06:07 pm:

I'll start with some explanation. Jump to the last paragraph if you just want the question. Thanks in advance!

The '25 I just bought has the cam nut sticking out beyond the step up on the camshaft by about 0.100". The second photo shows it best. I tried several different rotors on the shaft, and some shoulder out on the shaft step and others shoulder out on the cam nut. Essentially, some rotors have a short section of tube sticking out the backside (they shoulder on the shaft) and others don't have this so the arm of the rotor hits the cam nut before the unit can fully shoulder out on the shaft step. Even when this happens, though, you can still insert the rotor pin and since the rotor, cam, and cam nut are all turning together, the arm isn't really "rubbing" on the cam nut, rather it's just against it.

I see that the TW instructions make it very clear that if the cam nut extends beyond the step on the shaft, the nut must be shortened. https://docs.wixstatic.com/ugd/84c6a6_8177bce5ff8248f5a7fcb855f4b72c10.pdf Looking at the parts, though, the TW rotor does have a section of tube that extends beyond the arm. So, the tube should slide into the cam nut ID, allowing the rotor to shoulder out on the shaft, right? I don't have a TW, but was thinking of getting one. The modern seal was loose and backwards, which is what made me dig into this in the first place. It has a CR 9613 in it, which doesn't appear to be what others use (9853 or 9878). I'm aware of the OD variance and tricks there, though.
https://www.modeltford.com/item/3221CB.aspx

Here's the main question(s)...Is it normal for the cam nut to extend beyond the camshaft step? Does it just happen to depend on the cam and style of nut you're using, or does it indicate there's a problem? How would one know if the nut had backed off (loosened)?



Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Saturday, December 15, 2018 - 06:16 pm:

Your missing a seal, the shoulder on the nut is for a seal to run on, either the original felt one or a modern, if you are going with the TW then you need to fit a modern seal.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Saturday, December 15, 2018 - 06:21 pm:

Sorry re-read your question, yes the nut is to long, it should be shorter than the lip on the cam.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Saturday, December 15, 2018 - 06:33 pm:

I just tried a TW brush holder, it should have enough length and has a small enough out side diameter to fit inside what nut is overhang.
My be someone fitted a washer behind the nut.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Namdc3 on Saturday, December 15, 2018 - 06:51 pm:

Thanks, Frank!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith, Lomita, California on Saturday, December 15, 2018 - 07:05 pm:

You may have a fiber timing gear. That will do it, or another brand where the center part of the gear is thicker than an original Ford gear.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Adam Doleshal on Saturday, December 15, 2018 - 08:12 pm:

I concur with Larry. Its likely you have a thicker, fibre timing gear. Itís also possible, but less likely that you may have an improperly made front cam bearing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Namdc3 on Saturday, December 15, 2018 - 09:20 pm:

I just looked and it does indeed have a fiber cam gear. At first I thought it might be bronze looking through the oil fill hole, but I took the generator off and can tell its fiber by the feel and sound of it. All the teeth look perfect. The engine was rebuilt in 2005. I do not know if it was a new gear at the time, and the PO said it probably has 200-300 miles since rebuild.

Soooo, yet another topic of great debate. Some are cut and some are molded... many people hate them and blame crank breaks on them...many people run them a very long time without problems....sigh, nothing's easy.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Saturday, December 15, 2018 - 09:32 pm:

I do not recall any one blaming a crank break because of stripped teeth. ?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Namdc3 on Saturday, December 15, 2018 - 09:43 pm:

From what I read, some think the cam gear strips and the engine fires out of time (for example, early enough in the compression stroke to twist the crank backwards while running forwards). Just what I read, I don't have any experience or first hand knowledge of it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Saylor, Citrus Heights, Ca on Sunday, December 16, 2018 - 12:38 am:

I experienced a striped timing gear and a broken crank, apparently at the same time. On a tour many years ago going down hill long Curvy grade. Engine stopped running. Quickly found the striped timing gear. While tearing down to replace the gear, discovered the crank broke at an angle inside the center main. Always wondered if the the broken crank caused the timing gear to go or vice versa. Anyone else have both at once?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith, Lomita, California on Sunday, December 16, 2018 - 09:44 am:

I have a fiber gear in my '13. It's been in there for over 50 years. The timer brush must seat against the camshaft, so the timer brush needs to have a slot filed in it to seat against the cam.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Namdc3 on Sunday, December 16, 2018 - 10:16 am:

Thanks, Larry. I'm inclined to agree. On a front-contact timer like a New Day or Crystal, having the rotor against the cam nut and therefore not quite bottomed out against the camshaft wouldn't cause a problem (that I can think of) - it would just compress the brush spring slightly more. In a radial-contact timer, the roller/brush wouldn't be axially centered in its contact ring. I would think that as long as the lock pin goes in, the rotor would be considered back far enough. However, filing a small slot to clear the cam nut rim would allow the rotor to seat properly. Many rotors have an extended backside so the arm clears without a slot. From Franks's comment, the TW rotor will work without modification.

On a related note, I'm scratching my head trying to figure this paragraph from Snyder's nylon cam gear description..."This is a new standard,improved timing gear for the Model T Ford. It was made from the original Ford drawing. The gear is made of nylon 6, the web of the gear is thicker than the original metal gears. This requires the camshaft nut to be cut down to prevent the timer roller/rotor from shorting out on the cam nut. A cut down cam nut is supplied to use with this gear. No other modifications are needed.".....Why would it matter if the roller rotor shorts out against the cam nut? The camshaft, cam nut, and rotor are all in electrical contact anyway. It seems like the only thing you can't have short out is the 4 cover contacts to anything else or each other. Everything else (timing cover, shaft, nut, seal or shield, rotor, timer cover) touch all the time anyway. Right? Am I missing something? Maybe they meant so that the arm doesn't rub and mechanically hang up, not allowing the roller to freely ride the contact ring surface.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Adam Doleshal on Sunday, December 16, 2018 - 10:20 am:

Early cam nuts were shorter than later ones, so it is possible that a combination of fiber timing gear with early cam nut may not cause interference of the nut with the roller/contactor.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Adam Doleshal on Sunday, December 16, 2018 - 10:28 am:

The thicker nut WILL cause problems with a New Day timer. In normal operation on a correctly built motor, the brush is just about fully compressed into the brush holder and there is only about .030Ē clearance between the brush holder and timer inner face. With a longer nut, the brush holder bottoms against the timer and chews up the timer.

With a roller timer or TW timer, the contactor does not fully ride on the track, but most people donít realize there is an issue because it still runs, just has a shorter life.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Namdc3 on Sunday, December 16, 2018 - 10:43 am:

Thanks for pointing that out Adam. There's an S-style New Day on it now, and the arm barely hits on the nut. It must be within 0.030" of shouldering out in the shaft, because it seems to have been working okay. A couple swipes with a file on the backside of the arm will make it a non-issue, though. So, I have a fiber gear and S-style timer - both disliked on the forum. I'd really like to find a Leich Magnetic Timer, but have been unsuccessful in the classifieds. I have one on the '14 and really like it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Eubanks, Powell, TN on Sunday, December 16, 2018 - 10:50 am:

I would turn that pan bolt that is sticking up down with the nut on the underside. Looks like an excellent opportunity to short a timer wire.


Top of pagePrevious messageNext messageBottom of page Link to this message  By kep on Sunday, December 16, 2018 - 06:44 pm:

S style new days are fantastic! If you use a pure carbon brush.
If you have the opportunity, do try t.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith, Lomita, California on Sunday, December 16, 2018 - 09:32 pm:

I've never heard a good thing about a Snyder New Day. Stay away from them. If you don't file the slot I mentioned the whole timer case will wobble.


Top of pagePrevious messageNext messageBottom of page Link to this message  By kep on Monday, December 17, 2018 - 12:10 am:

Well now you have heard a good thing about them.
Trust me, they work.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Namdc3 on Monday, December 17, 2018 - 12:23 am:

Good catch, Jim. Larry, I don't follow the wobble comment. The rotor would be tight against the end of the cam nut via the nut on the end being tightened down. Yes, the brush would be compressed more, but so long as it didn't bottom out in the holder, it seems like it would run as normal. There's enough slop between the brush and brush holder to allow the brush to sit flat against the timer cover, even though the rotor would be cocked by any slop between the rotor ID and the cam OD. I don't see where any force to cause case wobble would come from. Not arguing, just scratching my head.


Top of pagePrevious messageNext messageBottom of page Link to this message  By kep on Monday, December 17, 2018 - 02:28 am:

I once had a .gif of the new kind running with the brush too tall.

Oh look, i found it, hope the image loads.
new day with brush a tad too long


Top of pagePrevious messageNext messageBottom of page Link to this message  By Namdc3 on Monday, December 17, 2018 - 08:07 am:

Kep, that would be so tall the brush is compressed all the way and it's still lifting the cap. Maybe that's what Larry meant. Mine was out by the 0.100" and still didn't bottom out the brush. Maybe it's a different brush that didn't come with the S timer originally. I notched it and verified that it will be about half compressed when assembled.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith, Lomita, California on Monday, December 17, 2018 - 12:38 pm:

The photo posted by kep is what happens if you don't file a notch in the brush.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Duey_C west central, MN on Tuesday, December 18, 2018 - 07:55 pm:

I bought my 18 with a timer just like that Kep! It's in a box now.
Hmmm, a notch you say Larry? Cool.


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