Cam Gear

fredski53

fredski53

Senior Member
Ok, I'm going to remove and replace the cam gear. I was looking at the Vendors catalog and some of them carry an "Over Sized" cam gear. .003 &.005 seem to be the most commen oversized gear. They also have a Standard gear. When would you use an oversized gear and how would you know to use one? Or should I just get the standard gear and go with that. The reason I'm replacing the gear is I had the engine overhauled 18 months ago, and the gear was replaced with a inferior one.
 
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Without know what the clearances are at the teeth we would not be able to suggest what size would be needed.
 
Was the crank gear replaced during the overhaul? How do you know current gear is inferior?
If it is running OK I'd leave it alone.
 
Its most common to replace BOTH gears together. That way there is no question that both should be at 0.000 oversize.

Should you decide to "recycle" a crank gear, buy each oversize available and try the one starting with smallest for "least free play." Be sure to run it all the way around lest one gear or the other be a little off center and get to a rub spot. Usually this is the cam gear. In fiber/composite they're none too centered and the two pin mount/clamp collar is not conducive to centralization.

And - if you do have a little "rub" - with the fiber it will wear down quickly. And - you likely have 0.002 "slop" in your cam bearing anyway.

This is one of those if everything in the engine is not brought back to "spec" - then you're kind of into "trial fit & error" anyway.

Joe K
 
I replace cam and crank gear as a set,tooth condition of the crank gear affects the cam gear life.Check backlash at four points 12,3,6 and 9 o'clock....004 to .006 with new gear.If engine has been rebuilt and line bored this dimension can change resulting in the need for an oversized gear.Metal gears can be noisy,cam plunger springs get weak.Crankshaft harmonic imbalance accentuates the issues.Ford used a fiber gear for quiet running and vibration tolerance.They are effective,the only drawback is they slowly degrade,altering cam timing slowly till the gear fails,the fiber sloughed off the gear finds its way to the oil pump screen and can cause engine failure.
 
If the main bearings get worn but still can be shimmed out, this puts the crank gear a little bit closer to the cam gear. When mains are repoured and align bored, the tooling is usually keyed off the camshaft to keep the tolerances there but it can still be off. It's a good idea to check the backlash between the gear set during heavy maintenance or overhaul. A feeler gauge or a dial indicator set can be used to check it. You just never know what you will run into with these old motors.
 
How much lash is there ? That may help determine the size. Anything over about .009" will make noise/rattle.

Like the others said, there are many variables involved.

I think .003" is a good bet, just measure once installed to make sure. Ideally lash should be in the .004-.006" range.

If I had to do it I'd use aluminum, but, now Snyder is offering a nylon gear available with 7º advance which sounds promising.
 
The Model T is the only one I see. If I was going to replace the gear I would use ether laminated or metal. The macerated gear is chopped up short fibers/binder compressed to make the gear. (If you understand how paper is made, same thing) The laminated is layers of woven fabric/binder compressed. The laminated are more $'s but you are buying a better product. How to tell the difference; the laminated you can see the weave from the fabric the macerated is smooth a bit like paisley print gone wild.:)
 
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Ok, I guess I should have explained more! I had the engine completely overhauled 18 months ago by one of the Vendors that advertise in the Restorer. Ever since I installed the engine there has been a LOUD KNOCKING when I take my foot off gas pedal to slow down, that is when I hear a loud knocking! I talked to the engine builder and he keeps saying there is too much timing. I've adjusted the timing and the knock is still there. Now, last week at our club meeting, one member mentioned that he had this engine overhauled at the same place and he is having the same noise problem! He took off the inspection cover and there are teeth missing on the fiber cam gear! He called the builder and the builder said they had a bunch of problems with the cam gear they used a few years ago! Now, I haven't call the builder, im not really happy with the work that was done. I just want the engine to run properly. I'm going to remove the inspection cover and see what condition the cam gear is in. I thought I would order a replacement gear, but I didn't realize there are oversized cam gears! So, if the gear is damaged, I'll end up calling the builder anyway, and see what he recommends.
 
Ever since I installed the engine there has been a LOUD KNOCKING when I take my foot off gas pedal to slow down, that is when I hear a loud knocking

You would never get knocking from too much timing advance when you take your foot off the gas. However many people run way too much advance when driving. I run mine 28-30 degrees with the lever all the way down and that is plenty with todays fuels.
 
You would never get knocking from too much timing advance when you take your foot off the gas. However many people run way too much advance when driving. I run mine 28-30 degrees with the lever all the way down and that is plenty with todays fuels.
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Per my go-to on these things (Vince Falter at fordgarage.com)

http://www.fordgarage.com/pages/bdistributoradvance.htm

The measurements above show that the initial static Model B ignition timing point of 19 crankshaft degrees BTDC plus a maximum mechanical centrifugal advance of 17 degrees equals a theoretical geometric maximum total advance of 36 crankshaft degrees. The slots in the centrifugal flyweights limit their travel and the timing advance.
Compare this to a Model A distributor which has an initial timing point at 0 crankshaft degrees TDC plus an actual manual maximum advance of 40 crankshaft degrees. The the breaker plate arm notch in the bakelite distributor body limits the travel of the plate and the timing advance.
The Model A ignition uses a zero crankshaft degree (TDC) initial timing point so that the engine can be easily started by hand crank, however it should never be run under load in this "retarded" position. The advance lever should always be advanced 1/3 to 1/2 travel (13 to 20 crankshaft degrees BTDC) on the steering column quadrant after starting the engine, and should generally not be run more than 3/4 advanced on the column under any normal circumstances.
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Bolded mine

Fuels today are more "knock resistant" (higher octane) allowing one a greater advance without knock, but there is a "mechanics" to advance too which is irrespective of the fuel. One wants the fuel combustion to occur in a range where the engine can best use it. Just because it doesn't knock the head off doesn't mean you CAN do it - or want to.

Joe K
 
How do you guys feel about the fiber cam gears? What is the benefit? I feel it might be more quite, but that the wear would be premature, and only end up in the oil and the rest of the motor... Where a magnet on the belly of the pan, as well as the factor style "steel gear," your shavings will be heavier and would have a better chance of it collection in the belly of the pan.

Matt
 
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I had a laminated gear installed several years ago and it has run perfectly, with no noise. I would not use the ordinary fiber gear......
 
I prefer metal cam gears and haven't noticed any noise as a result . I figure that the main reason that cam gears that aren't metal fail q is because of the use of a rag between the gears to lock them in place for installation . The rag puts a heavy strain on and weakens the cam gear teeth . I prefer to remove the side timing gear cover and use a C clamp to lock the gear against the side of the engine block . Using a rag between the gear teeth isn't nearly as good a method as I first thought .
 
Had some chatter,removed the plunger spring and installed a set screw to make the plunger a thrust button,better but not happy..installed a harmonic balancer and all is good..I went with the 6 sided timing gear nut,just touch it with an impact wrench,off or on

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