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Old 09-15-2019, 07:41 PM   #1
Fordfan29
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Default Timing gear/cam noise?

About 10,000 miles ago I changed my bronze cam gear (worn just beyond spec's), replacing it with another bronze gear & a matched crank gear at the same time. After about 5000 miles it developed a knock at about 43 mph in high & a knock at about 53 in high & overdrive that has continued to get worse. Either side of those speeds the engine ran fine but recently began to knock occassionally at idle. I've opened up the engine & checked the distributor drive gear and adjusted the valves since they were needed. Nothing changed as far as the knock. Checking the timing gears I found the bronze gear worn beyond the 0.003-0.005" specified (0.010). I had installed the gears with an original cam thrust spring and I shimmed it to the 35 lbs. at the assembled height. My question is how to control the cam thrust because I think the bronze gear wear is from the cam moving forward & back.
I tested a new thrust spring with the same shims & found it to be 45-47 lbs. at the same installed height. Is this too much pressure on the cam? I have driven my car a bit over 80,000 miles and moved to metal gears for dependability years ago.
What life should I be expecting from bronze or aluminum gears?

I'm open to any suggestions.
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Old 09-15-2019, 09:40 PM   #2
Railcarmover
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Default Re: Timing gear/cam noise?

I drilled my timing cover and tapped it 5/16nf and used a long allen to turn the spring loaded plunger into a thrust button..tighten the allen home,back it off a 1/4 turn,.oo5 end play,problem fixed

Had the same problem with thrust,upgraded to a bronze and new crank gear,still had the issue.Im running high compression and a C grind cam,figure a greater thrust a by product of higher valve load.
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Old 09-16-2019, 05:06 AM   #3
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Default Re: Timing gear/cam noise?

I had a similar problem. My fibre gear would knock quite loudly at idle. I tried various things to remedy this. After fitting a new aluminium gear and steel crank gear and drilling the timing cover for a thrust bolt I ended up with a rattle like piston slap at 3 different rev bands. It came and went as the engine travelled into and out of these rev ranges. After fitting a rubber harmonic balancer from Murray Horne in New Zealand the annoying rattle is gone, but there is still a rhythmic knock at idle. Replacing the timing pin with a polythene bolt removes the knock like magic when it contacts the rotating gear. Not a usable solution since the plastic bolt wears away quickly, but certain proof that it is the gear knocking, not something else. Tooth backlash was very tight when the gears were installed.
Engine was stripped to investigate what I thought was piston slap, but piston clearances were all 0.0035 to 0.004 as when the motor was assembled about 20000 miles ago.
I think harmonic vibrations of the crankshaft vibrate the two gears together causing the rattle and the harmonic damper damps the torsional winding up and unwinding of the crank, removing the rattling noise.
On the basis that "If a little bit is good then too much is better" I put a damper on our fibre geared, counterweighted crank Tudor engine and the almost subliminal noises that I could hear and my wife could not have gone on that engine too and it just sounds so much smoother at all speeds now.
I suspect that vibrations that occurred above 2400 engine rpm in a standard motor have been moved down into the running range by counterweighting the crankshaft in both my engines.
Others have the same experience. Look up my earlier posts in my profile for a lot of history and access to other members findings.
There has been a great deal written about noisy cam gears.
SAJ in NZ
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Old 09-16-2019, 05:12 AM   #4
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Default Re: Timing gear/cam noise?

Quote:
Originally Posted by Railcarmover View Post
I drilled my timing cover and tapped it 5/16nf and used a long allen to turn the spring loaded plunger into a thrust button..tighten the allen home,back it off a 1/4 turn,.oo5 end play,problem fixed

Had the same problem with thrust,upgraded to a bronze and new crank gear,still had the issue.Im running high compression and a C grind cam,figure a greater thrust a by product of higher valve load.


Food for thought here, ...higher valve loads should not make the Camshaft walk fore & aft by itself. Besides a oil pump applying greater pressure, worn Tappet bores and/or worn Camshaft journals would/will typically cause the Cam to walk. If the Tappets and the Cam are perfectly perpendicular to each other, there should be any side loads or thrusting caused by the extra valve train pressure.
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Old 09-16-2019, 07:55 AM   #5
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Default Re: Timing gear/cam noise?

I did a bunch of investigating on mine without finding a root cause,cam bores measured out good,tappet bores measure out good,gear backlash spot on in four positions.No tooth wear that would indicate a 'heel or toe' condition that would indicate misalignment of the crank/cam..I realize that isn't a true indicator of misalignment,which if it did exist I'm going to run anyway.
Inspected oil pump,I polished the lower plate during rebuild,no wear on it currently,shaft straight,no apparent side loading.Cam drive gears good,no lifting when spun no load..I couldn't put a finger on the issue,my thrust from valve load was a theory,not a conclusion,which is why I put 'I figure' in the statement.

Imagine it would take a large offset of cam or tappet bores to force a 35 pound spring.Ford did use a fiber gear to lessen noise.

That is one possibility,the oil pressure..there doesn't appear to be any modification to raise pressure,but I didn't investigate based on that assumption..given the previous owner ran a 'pressure' line to center main and an additional crankcase vent at the back of the valve cover that does bear investigation..Ill be taking the engine back out soon,that will be checked..

converting the spring loaded plunger to a thrust button cured the symptom.I don't believe it bears that much greater of a load than the spring.with the engine idling I can turn the thrust screw by hand,once again not precise,but I was concerned how much force is being applied to the thrust button.
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Old 09-16-2019, 08:08 AM   #6
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Default Re: Timing gear/cam noise?

Quote:
Originally Posted by SAJ View Post
I had a similar problem. My fibre gear would knock quite loudly at idle. I tried various things to remedy this. After fitting a new aluminium gear and steel crank gear and drilling the timing cover for a thrust bolt I ended up with a rattle like piston slap at 3 different rev bands. It came and went as the engine travelled into and out of these rev ranges. After fitting a rubber harmonic balancer from Murray Horne in New Zealand the annoying rattle is gone, but there is still a rhythmic knock at idle. Replacing the timing pin with a polythene bolt removes the knock like magic when it contacts the rotating gear. Not a usable solution since the plastic bolt wears away quickly, but certain proof that it is the gear knocking, not something else. Tooth backlash was very tight when the gears were installed.
Engine was stripped to investigate what I thought was piston slap, but piston clearances were all 0.0035 to 0.004 as when the motor was assembled about 20000 miles ago.
I think harmonic vibrations of the crankshaft vibrate the two gears together causing the rattle and the harmonic damper damps the torsional winding up and unwinding of the crank, removing the rattling noise.
On the basis that "If a little bit is good then too much is better" I put a damper on our fibre geared, counterweighted crank Tudor engine and the almost subliminal noises that I could hear and my wife could not have gone on that engine too and it just sounds so much smoother at all speeds now.
I suspect that vibrations that occurred above 2400 engine rpm in a standard motor have been moved down into the running range by counterweighting the crankshaft in both my engines.
Others have the same experience. Look up my earlier posts in my profile for a lot of history and access to other members findings.
There has been a great deal written about noisy cam gears.
SAJ in NZ
I agree there is a inherent load /unload condition of the cam/crank gear,I believe its the reason ford used a fiber gear,and a spring loaded plunger to counteract it. Stands to reason a harmonic balancer would help, dampen torsional impulse.Just installed a steel pulley to avoid the catastrophic potential for failure of the cast original,might go with a balancer in the future.
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Old 09-16-2019, 08:44 AM   #7
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Default Re: Timing gear/cam noise?



I stole this picture...and copied the work too but thats what I did to mine Fordfan29
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Old 09-16-2019, 09:44 AM   #8
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Default Re: Timing gear/cam noise?

Quote:
I shimmed it to the 35 lbs. at the assembled height
For reference, how much is the assembled height?
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Old 09-16-2019, 11:17 AM   #9
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Default Re: Timing gear/cam noise?

I've never had that problem, but cam lobes are ground on a taper to induce tappet rotation. The timing gears and the dist/oil pump gear produce thrust towards the rear. That's the theory anyway but I've found that dumb things, like iron and other metals, don't always know about theory. I also use a bolt in the plunger to control movement on my Bonneville engine but noise on a race car is too loud for me to notice any small noise.
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Old 09-16-2019, 01:56 PM   #10
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Default Re: Timing gear/cam noise?

I've done the plunger screw in the cover mod with bronze gear and hardened crank gear. Still cam knock and .010" end play initially had .004" when new. Now after pulling the pan off I find all of the bronze worn from the gear in the bottom of the pan. I can tighten down the screw and after 15 minutes it starts knocking again. Im going to machine some new parts internal to the the plunger again to see if it holds. I doubt it will last but will give it another try. I have a Stipe B 340 cam with adjustable lifters, lash checked good, new valves with modern stems, cam bores were good and measured parallel to the crankshaft bores, stripped the fiber timing gear at 6,000 miles new pump drive, shaft and rebuilt distributor and new oil pump when the short block was done just under 10,00 miles. Everything turns good. Burlington crank was new before the stripped first timing gear. Maybe .004" lash when new is too much but to find .010" lash after the few miles with the bronze down in the oil pan, I'm very unhappy. The engine is too loud to hear the cam bounce at higher rpm, but very noticeable at idle. Pretty sad to think I spent that much money on a short block getting it inserted with so many new parts, and replaced it with a cheap swap meet diamond block that i did a refresh with rings and valve lap with a regrind cam and fiber gear that runs ok and is much quieter.
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Old 09-16-2019, 02:04 PM   #11
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Default Re: Timing gear/cam noise?

What's annoying is not being able to find the root cause.I have a real nice late B cam now,but I had the same issue with a regrind to B spec A cam ..so atleast in my case I can rule out the cam
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Old 09-17-2019, 10:49 AM   #12
Jim Brierley
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Default Re: Timing gear/cam noise?

.004" is more than enough, .002" is all that is needed because the only consideration is expansion on about 1.5" of steel cam.
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Old 09-17-2019, 11:21 PM   #13
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Default Re: Timing gear/cam noise?

Thanks to the information I have received on this forum and on another, my car is healing and should be on the road again soon. I'm impressed with all the fixes suggested. I'm installing a 5/16" fine thread bolt inside the plunger through the timing gear front cover with a locknut. A new aluminum gear is installed. I'll be starting with 0.010" clearance and see what happens.
There have been a few conversations started within the local club about timing gear noises and cures. All of this information advances those that want to learn so we can continue to drive and enjoy our Model A's. It is good to know so much help is available. Thank you.
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