Timing gear knock

SAJ

SAJ

Well-known member
When I got my roadster I imported a touring engine from Snyders, reconditioned by Schwalms. It ran nicely until I burned No. 3 exhaust valve.
I removed the head, replaced the valve and since then I have had a camshaft knock that I diagnosed as end thrust "walk" by screwing in a polythene bolt in place of the timing pin, wherupon I could remove or return the knock at will by pressing it onto the fibre cam gear.
First I checked everything was free in the oil pump and distributor drives, mindful of what James Rodgers has said about this. Then I replaced the spring in the plunger and made a packer of about 0.3inch to put inside the plunger. This made no difference.
So I then tapped the casing and put in an adjustable end thrust bolt.
Again, the noise is still there, unabated.
I just removed the side plate to observe the gear running and a video is attached here https://www.youtube.com/watch?v=iPLZXvFUf9E (There is a bit of gasket hanging into the housing at the top, but doing no harm)
I then put the poly bolt in the timing pin hole and observed it eliminating the knock as seen in this video https://www.youtube.com/watch?v=MmKJyDLO1cM
Lastly I measured the backlash with a DTI at 0.008 inch as in the photo attached (measured in 4 places around the gears).
I know it should be .003 to.005, but I did not think a fibre gear would be so noisy at 8 thou backlash.
Plus, if I replace it, would I get an oversize gear?
The last video shows the gears meshing and there are no teeth missing etc as you can see. It all looks good to me. http://youtu.be/L0qaBGVlhgs

I know metal gears are said to be better in a matched set, but I don't want to remove my engine to get the C/S gear off, because I already have two other members cars in bits as favours and I am short of time before rallies coming up.
Diagnosis and advice please. I don't understand why the noise only started when I replaced the head gasket and valve. Nothing else was done except a valve grind all round.
Merry Christmas to all
SAJ in NZ
 

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I would suggest checking the lash again in 4 equal spots at 9,12,3, and 6 oclock on the timing gear and marking the spots to make sure it is even all the way around. If it is then I would try a .003 oversize timing gear and see what that does. I agree I would not go to the metal gears right now. Honestly I have always used the high quality fiver laminated gears and they have done well. Lots of debate on this but henry ran the fiber gears up through the flathead V8 era and they did well. If it was that much of a problem they would have switched it out long before as there were 5 million "A"s out there plus V8's with the same type of gears. Think about it!

Anyway... I would also make a call ( maybe first) to Snyders and Schwalms who both have excellent reputations and address the issue. Your videos are somewhat misleading as the last one has a clicking noise which seems to me the bolt or piece you used to put in the timing pin is clicking on the dimple on the gear every time it goes around. A stock spring and plunger should do the job on the camshaft cover for end thrust. Again, chat with Schwalms and Schneiders. I believe it's in your best interest to do so.
Larry S
 
Larry what has been stated by several members is that the quality of the fiber gear was much better back in the day. Today's gears, even the laminated ones, are not as robust. If you have the opportunity to tear down several engines which have used the available modern fiber gear you will see the difference. I have never removed one that was fully intact
 
Thanks Larry, Vince and T'BIRD During the tests the front cover was removed, a clamp put on the gear and the proper spanner put on the nut and I exerted about 60 ft lb on it before the clamp slipped. There was no movement. I know it should be tighter than this so I may re-test to a higher value, but I saw no signs of looseness.
TBIRD, funnily enough I used to manufacture Formica DF105 Phenolic Fabric for gears, so I know the quality can be very high if well-made. We pressed and cooked 8ft X 4 ft. sheets in various thicknesses at 2400 psi and the gears for Fords etc were cut from this. A very good self-lubricating material for bushes as well as gears etc.
This was woven cotton fibre impregnated with a Bakelite-type resin and layered up to required thickness. I was Technical manager at Formica here in charge of all formulations, processes and engineering for many years in the 60"s and early 70's.
The gear I have looks OK. I will wash it off and look again.
Larry the clicking noise is definitely not the polyethylene bolt moving over the indent. It is quite a lot bigger than the indent and I took 1/2 and1/8 speed videos of the bolt being screwed in to check this. Videos do play tricks and the knock is only when the bolt is clear of the gear and goes completely when it contacts the gear.
My thoughts were that the poly bolt can either eliminate end walk, which the thrust bolt in the centre should also do, or damp the backlash by friction or damp wobble from a loose gear. I have another video where I leverd on the gear to observe looseness with a DTI attached and I saw only about 0.010 flex axially at the rim of the gear. I am left with backlash as the cause. I could imagine an ally gear knocking at maybe 0.010 backlash. But 0.008 inch seems rather small to produce the level of knock I hear at Idle with an absorbent fibre gear. Am I wrong here? It cannot be heard when driving, but I love to listen to a quiet idle next to buses at traffic lights etc!
In view of Vince's advice i will check tightness again, and remove the gear to examine the pins. And get an 0.003 gear from Snyders too.
Re Schwalms, I have done 10,000 miles since they reco'd it and 9000 of those did not knock. And I do not think Ora Landis will want to hear about it in view of that. The engine is a real performer and the burnt valve was caused by my letting someone else work on it while I was too busy running my own company here.
Thanks again fellows for your advice.
I will post when the problem is solved.
SAJ In NZ
 
Hi Tom,
No I havent had the sump off this one. It has pressed on and pinned counterweights according to what Ora Landis told me. Are you suspecting the knock is mains?
It is very quiet and smooth at speed. Has a Mitchell O/D and pulls well over 70 mph on my GPS. When I get time I will drop the pan and see but I have to fix several other members cars first.
I am interested in why you ask though.
SAJ in NZ
 
I would think your mains are fine since you have the best weights on your crank.
I only asked because the center main usually wears first on a crank without counterweights.
 
I am relieved to hear you say that Tom.
I respect your advice and opinions greatly.
Do you think .008 backlash measured accurately with a DTI can make a loud knock at idle as in my videos?
I am going to remove the gear just to check it, but dont think I can get the crank gear off without pulling the motor.
Re middle main I have a posting showing a members broken babbit after only 15000 miles on a non couterweighted crank. I am still deciding how to fix it.
SAJ In NZ at midnight.
 
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SAJ I think you have it pretty well nailed your test shows that loaded there is no knock
that tell me it is play in the gears 0.008 is enough back lash to make the knock
I would also have a close look at the crank gear where it is notched for the key had 1 crack there a few years back
 
If it started after a new valve, it sounds like some thing might be wrong there.

Why did the valve in a rebuilt engine go bad?

Did you grind the end of the new valve by hand, to make it have more clearance. If so and it is not square it could put the valve in a bind in the guide.

When I run a hot cam in an A engine. I drill and tap the plunger hole in the cover for a bolt. In the end of the bolt drill it for a piece of bearing bronze. Then screw that through cover and inside the plunger until you get the proper end play in the cam. Not that hard to do and might fix your problem. But I would want to know why it is making a noise.
 
Vince has an excellent point and could absolutely be the problem . Kudos vince for that. It takes 15 minutes to pull the front cover. Less time than fordbarn.
Go check it out I've had older cloyes gears do the same type if thing where they got loose in the aluminum hub.

Tbird I understand your comments and appreciate them you never quit learning about this stuff every day .
Larry
 
Another long shot is a dist shaft that is binding. maybe dry shaft or the locking screw to tight, which will bind the shaft. The odds are that it is some thing that was done when fixing the valve. most people do not want to hear this.
 
What clearance are you using for the camshaft end play? I tighten the center adjusting bolt like you installed to .003 cam end play and have no noise. I think that if you still have that knock with .003 end play, the problem is not cam walk. Also, the noise I have heard from excess gear clearance is more a rattle sound than the knock you have, and fiber gears are pretty quiet.
Maybe its just me, but is the cam gear wobbling a tiny bit? I would first check the end play, then pull the gear and check for fit and tightness. See if the gear moves when just held by the dowels. Then go back and check eveything you did before the knock started.
 
Thanks for the follow ups. Answering them in the order they came:
Colin, I will check the crank gear when I get to work. I still find it hard to believe such a heavy knock can arise from backlash of a fibre gear.
George.I left the car for Diff work with someone.They reset the timing by ear and it was very retarded and the engine seized while driving it back to my workshop. No damage to bore or rings after it cooled, but I surmise the No. 3 valve overheated and warped. I didn't find anything else to cause it. New valve tip not ground. I have adjustable lifters etc. Cam thrust plunger already replaced by an adjuster bolt etc, and this does not remove the knock. Replacing the timing pin with a Polythene bolt does remove the knock with little pressure exerted on the rim of the gear. see videos attached, (which were in the wrong order and have just been fixed!).
Distrib. shaft etc all free - first things I checked. Can't be "cam walk" anyway since the adjustable thrust on the front cover would remove or at least improve it. I would love to find it was something I did, actually, so then I could fix it! I do not profess to be an expert on these engines in any way. I learn each time I mess with anything.
LARRY. Front cover is off, Gear nut tight. Will remove the gear anyway and get in a standard and oversize one from Snyders for trial fitting.
PC/SR. have tried .003 end float (DTI on gear) and screwing it in full tight while running ( dangerous because the front cover flexes a lot!) and neither changed the knock , whereas a slight twist on the poly bolt in the timing pin hole immediately removes the knock. I agree the gear does seem to wobble, and in time with the knock. But turning slowly by hand crank, it seems stable. Backlash 0.008 was measured at 4 points at 90 degrees. but the gear looks eccentric in the videos nevertheless. I will take it off and measure over pins in teeth to be sure.
As you say, I would expect more of a rattle than a synchronized knock with fibre gears, so I have to suspect the gears themselves.
Thanks again for all the advice
SAJ in NZ
 
engine seized while driving it back to my workshop.

I would bet this is where your noise is coming from. I do not think it is the gear. I think you will find it when you start driving it.
I hope I,m wrong.
 
I agree with George. After just learning this bit of information I would look for a collapsed piston skirt on #3 piston.

I'm taking my engine apart to see what the ticking is. My engine had several overheats and I think my engine has a collapsed skirt on #3 piston also.
 
Thanks for the replies. Interesting thing about collapsed piston, but the noise is only at idle and goes away when I press on the timing gear periphery with a poly bolt in the timing pin hole. And my experience is piston rattle is typically when cresting a hill and just backing off, especially when cold. And when revving in second under lighter loads. My knock is only when hot and I hear nothing under power or on over-run.
There were no signs of picking up in the bores when I had the head off and the engine only barely nipped and then freed quickly when it cooled, because I was quick and watching the temperature gauge because performance was a bit sluggish with the retarded spark. I had a bore scope into the cylinder while it was still nipped up too, because it happened just as I reached my workshop, probably from heat soak I had just driven down a motorway).
I now have an EGT in the manifold right next to no. 3 ex. just to keep an eye on things.
I hope you are all wrong! You may not be!! I will certainly keep this in mind as I investigate further. Thanks again
SAJ in NZ
 
I just realised, after the seizure I drove the car for several thousand miles before determining power was down, as the valve seat got worse and leak down increased and compression in no 3 diminished. There was no knock during this time. Only after the valve service did the knock appear.
Does it seem as if I am desperately avoiding thinking about a collapsed piston? I know I am!
SAJ in NZ
 
use the bore scope again and check for scoring now

piston slap can be evasive and not be consistent and can fool you. If you have no scoring I doubt you have slap. Use the bore scope all 4 cyls.... a great invention!
 
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