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Old 04-14-2019, 08:22 AM   #1
Tim R Hansen
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Default Timing Gear Back Lash

I have read that if there is up to .010 that it would be noisy. I do seem to have a tapping sound and wonder how much is coming from the timing gear. I pulled the plugs and when I rotate by hand I can hear a distinctive clang every time the lifters go over center. Would this indicate too much back lash?
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Old 04-14-2019, 08:32 AM   #2
James Rogers
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Default Re: Timing Gear Back Lash

This would only happen with aluminum cam gear. Fiber gears won't be noisy with .060 clearance. I have seen this. You probably need to check the valve adjustment or bearing clearance.
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Old 04-14-2019, 11:53 AM   #3
Jim Brierley
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Default Re: Timing Gear Back Lash

The noise you hear could be gear backlash, or tappets that are loose in the block, from normal wear. The answer there is oversize tappets.
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Old 04-14-2019, 12:25 PM   #4
Patrick L.
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Default Re: Timing Gear Back Lash

Cam gears can be noisy if too loose [ .010"+]. Most engines back in the day had fiber cam gears and I've changed more than I would have liked to because of that problem. One way to check is to use the timing pin. Very carefully with engine running push the pin into the gear and see if that helps with the noise. Removing the fan belt is a bit safer.

However, it doesn't sound [pun] as though thats your problem. I agree with loose lifters, either worn in the bores or excessive lash. But I'd also recommend looking at the distributor drive. Your noise sounds strange to me.
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Old 04-14-2019, 02:50 PM   #5
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Default Re: Timing Gear Back Lash

I had a knock also and it turned out to be my timing gear was worn badly. Here are a couple of videos of the sound the timing gear was making while running, hand cranking with the cover off and after a new timing gear.

The knock:
https://youtu.be/3R3eLKlvVmU

Hand cranking with timing cover off:
https://youtu.be/lDI6grnm-Z0

After new timing gear:
https://youtu.be/C-MMJRXug8E

I hope this helps.

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Old 04-14-2019, 04:18 PM   #6
Tim R Hansen
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Default Re: Timing Gear Back Lash

Exactly the sound I have. I was able to rotate the crankshaft to a position where I could rock the timing gear by hand and make the noise. I put a .003 oversize about 20000 miles ago so I guess a new .005 should help. When you put the new gear on and turned it by hand did it still make some noise?
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Old 04-14-2019, 04:43 PM   #7
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Default Re: Timing Gear Back Lash

I was driven crazy by timing gear noise. As my motor was modified with a reprofiled camshaft, I fitted an alloy timing gear, but the noise was almost unbearable. I then fitted a matched pair of steel and Bronze gears, but the noise was just as bad. I also fitted a new spring to the plunger and when that didn't make any difference, I packed behind it to apply more pressure and that made no difference.
Finally I fitted a Harmonic balancer pulley and the transformation was miraculous.
The re-profiled camshaft certainly has a more aggressive profile and with only four cylinders, the camshaft is oscillating as it pushes a valve open then is rapidly pushed closed. The new pulley somehow evened that all out and at the same time removed a couple of noticeable vibration periods in the motor.
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Old 04-14-2019, 05:03 PM   #8
Garagekulture13
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Default Re: Timing Gear Back Lash

I replaced the timing gear as well as the crank gear. The crank gear had some pitting and the cam gear teeth were badly worn as you can see in the pictures. The knock went away after I replaced them both.

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Old 04-14-2019, 07:11 PM   #9
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Default Re: Timing Gear Back Lash

Checking and changing the crank gear when needed is a good point. A bad crank gear can eat up a new fiber cam gear.
The cam gear is fairly easy to change, the crank gear not so much.
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Old 04-14-2019, 07:45 PM   #10
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Old 04-14-2019, 08:09 PM   #11
Tim R Hansen
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Default Re: Timing Gear Back Lash

Yes I would love me to change the crank gear but with the engine in the car it would be difficult I suspect. Anyone have any tips?
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Old 04-14-2019, 08:18 PM   #12
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Default Re: Timing Gear Back Lash

pull the engine ...it makes the job easier and you can work comfortably.If your timing gear is tired its a good chance the rest of your engine is tired as well.its a good time to check bearing clearances,hone and fit a set of piston rings and do a valve lap job..you can overhaul an engine without breaking the bank if you catch it soon enough.
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Old 04-14-2019, 08:52 PM   #13
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Default Re: Timing Gear Back Lash

Quote:
Originally Posted by Garagekulture13 View Post
I had a knock also and it turned out to be my timing gear was worn badly. Here are a couple of videos of the sound the timing gear was making while running, hand cranking with the cover off and after a new timing gear.

The knock:
https://youtu.be/3R3eLKlvVmU

Hand cranking with timing cover off:
https://youtu.be/lDI6grnm-Z0

After new timing gear:
https://youtu.be/C-MMJRXug8E

I hope this helps.

Sent from my SM-N950U using Tapatalk

Thanks for posting. Seeing/hearing the issue is great. Sound is completely different than a Babbitt or rod knock. You can describe a sound all day, but nothing beats a video with sound, and showing what a worn out timing gear looks and how it acts.
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Old 04-14-2019, 11:13 PM   #14
Ruth
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Default Re: Timing Gear Back Lash

Quote:
Originally Posted by wensum View Post
Finally I fitted a Harmonic balancer pulley and the transformation was miraculous.
The re-profiled camshaft certainly has a more aggressive profile and with only four cylinders, the camshaft is oscillating as it pushes a valve open then is rapidly pushed closed. The new pulley somehow evened that all out and at the same time removed a couple of noticeable vibration periods in the motor.
I have never seen a Harmonic balancer pulley for a Model A. It sounds like an excellent idea. Are they only available in New Zealand?

Last edited by Ruth; 04-15-2019 at 06:05 PM.
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Old 04-15-2019, 03:09 PM   #15
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Default Re: Timing Gear Back Lash

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I have never seen a Harmonic balancer pulley for a Model A. I sounds like an excellent idea. Are they only available in New Zealand?
They are available at your nearest machine shop. They can be made from several different late model big block dampers.
I use big block Chev. They require the least modification.
They need to be big and heavy. The perfect situation would be for it to be the same weight as the flywheel/clutch assembly. Since this is not normally something that can be achieved, we just make the damper heavy. The big block Chev weighs about 12 lb. You will need to trim the front cross member to use this.
It will not help much on felt vibration but will sure extend the life of your crankshaft due to less torsional vibration.

Here is a pic of one installed on an engine that ran 100% nitromethane many times. That crank is still running.
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Old 04-15-2019, 03:09 PM   #16
Patrick L.
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Default Re: Timing Gear Back Lash

Changing the crank gear in the vehicle can be done with some difficulty. The front of the engine needs to be jacked quite high. The radiator needs to come out, the rear motor mounts need to be loose and the one mount bolt on each side should be removed. The gear is really on the crank and usually takes serious heat and a real puller to get off. When putting the new gear on, do not beat/pound the gear on. Press it on. I use a length of turned pipe closed and drilled at one end so a bolt the same thread size as the crank can be used to press/push the heated gear on.
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Old 04-15-2019, 03:54 PM   #17
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Default Re: Timing Gear Back Lash

Quote:
Originally Posted by Ruth View Post
I have never seen a Harmonic balancer pulley for a Model A. I sounds like an excellent idea. Are they only available in New Zealand?
The new Zealand made Damper is the same size as the original pulley but only a little bit deeper. The cost including shipping is very reasonable. "These dampers are made by Murray Horn in Levin N.Z. His Company is Engine Restorations Ltd. His email is horn@xtra.co.nz
Murray says this is the best way to contact him.
The dampers are a straight fit to replace the standard Model A pulley. An added benefit is a shallow reverse scroll in the rope seal area to help contain oil.
"
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Old 04-15-2019, 06:08 PM   #18
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Default Re: Timing Gear Back Lash

Thanks for the info wensum. Can you use the stock 'ratchet nut' with the damper?

And Pete thanks for the info on the BBC damper. Not sure I want to cut my front crossmember tho.
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Old 05-07-2019, 11:49 PM   #19
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Default Re: Timing Gear Back Lash

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Originally Posted by Ruth View Post
Thanks for the info wensum. Can you use the stock 'ratchet nut' with the damper?

And Pete thanks for the info on the BBC damper. Not sure I want to cut my front crossmember tho.


Yes the replacement harmonic balancer pulley simply replaces the original pulley. However, due to its extra depth it sits quite close to the front spring U bolts, and it is necessary to install the fan belt before fitting the pulley as one can't feed a fan belt in once the pulley is installed
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Old 05-09-2019, 05:27 AM   #20
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Default Re: Timing Gear Back Lash

I carry a linked belt in both cars with the harmonic balancers. This makes it easy to replace a broken belt. These linked belts are good for tens of thousands of miles.
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