Timing gear teeth...??
 

Bert's sells timing gears that are .003 over, .005 over and .010 over standard....

I called and that is the width of the teeth and not the diameter of the gear...

But, they did not know the width of a standard sized gear's teeth...

does anyone have a new one that they can measure..?

My old one measures .110 and there is .040 of gear lash...

I know I should replace them both, but a full rebuild is in the future so I'm trying to keep this project simple....

Randy

Re: Timing gear teeth...??
 

cj5 - What you have stated " that is the width of the teeth and not the diameter of the gear" isn't making sense to me.

After talking to Dan McEachen (the who makes oversize gears); he states the over standard measurement refers to the center to center distance from the crankshaft to the camshaft.

I wonder if there was a misunderstanding?

Re: Timing gear teeth...??
 

Uh ?? Surely this is an absolute unalterable measurement .

Re: Timing gear teeth...??
 

Making the teeth wider would work just fine.

That is why you should get the distance correct between the crank and cam. There is no reason not to.

Re: Timing gear teeth...??
 

I will try to answer both, with what i know......

You have to understand that Bert's oversize gears are Bert's, and no one elses. I asked them if the "oversize" referred to the diameter of the gear or the width of the teeth, he said the width of the teeth...

I do understand that Dan McEachern makes oversize gears that are over sized in diameter, to compensate for the spacing of the cam and crank depending on where the babbitt gets line bored....

I think we are discussing two different products...

Re: Timing gear teeth...??
 

Ah yes the teeth must get wider as the diameter of the cam wheel gets bigger( unless you bung in an extra tooth!) but crank shaft centre to cam shaft centre is fixed and unchangeable.

Re: Timing gear teeth...??
 

I guess I need to ask what condition the crank gear is in ? A bad one can eat a cam gear fairly quickly. As your lash is .040" I'm wondering if thats the case.
At .040" it must make a heck of a racket.
I'm thinking it would be hard to come up with an answer other than trial and error. I doubt they would let you return a gear once its been installed and checked for clearance.

Re: Timing gear teeth...??
 

Yes, that is what I was thinking.....this cam gear is a fiber one and does not look that bad...but obviously it is worn.

I measured the lash again with a dial indicator and got .036...

Width of the cam teeth i sampled was about .108 to .110

If I knew what a new standard gear tooth measured I might be able to make a lucky guess and only buy one gear.

I know the solution is to buy both, but I do not not have a press ....maybe it's not necessary?

I'm planning a full rebuild in the next 6 months or so so this was really just a clutch and cam gear replacement and checking the bearing clearances...

Tough to tell anything from the pictures....

Re: Timing gear teeth...??
 

You don't really need a press to get a new crank gear on. I just heated the gear and it went on without too much fanfare just using the crank nut to press it on. Of course, the cam gear is just on there with it's silly nut (unless you have one of the new kind that takes a regular socket.)

Re: Timing gear teeth...??
 

I do notice something in the pictures that may be issue.
It looks to me that the crank and cam are not parallel.
If you look at the crank gear tooth surface on the drive side, it shows even wear across the face of the tooth. The idle side shows only contact on the rear half of the gear indicating that the rear CL is closer than the front CL.

It probably does not make or break the setup, however, it would accelerate the wear of one of the gears, probably the non-metallic one.

Put in a new composite gear and measure the backlash, then drive it.
It will more than likely last for a long time.

John

Re: Timing gear teeth...??
 

Well maybe I'll just order both then....A new crank gear and a new standard cam gear....and i have the silly nut...perhaps i should also get one of the hex-head replacements...

Re: Timing gear teeth...??
 

Thanks John, I noticed that also but did not know what it meant...the crank end play is a little out of spec...maybe that would cause the odd wear pattern?

Re: Timing gear teeth...??
 

If you are doing a full rebuild in 6 months, why not just run with these two gears until that time?

Re: Timing gear teeth...??
 

That is a thought for sure....but 6 mos is not a hard and fast date....and I'd like to improve this engine if I can, as long as it's apart.

Re: Timing gear teeth...??
 

I am not sure that the end play would cause the wear pattern like this.

If it was me, I would just replace the gear and start planning.

Do you have any idea how much mileage is on this motor?

All the Best, John

Re: Timing gear teeth...??
 

John,

The mileage is unknown. Since 1962 I doubt if it's seen more than a few thousand miles..the speedometer never worked.....but the 1930 engine and 4-speed were installed before we owned it.

I do not have the right tools but my best measurements show the bore to be .060 over.

It ran well enough, but was down on power...noticeable on hills, but it would do 45 on level roads...

Re: Timing gear teeth...??
 

Not sure I understand how over size gear teeth fit between the crank gear teeth that space is only so wide ???

Re: Timing gear teeth...??
 

FWIW:

Some Model A owners have had problems with either noisy timing gears; and/or rapidly wearing timing gears caused by non-aligned and non-parallel crankshafts.

Dan will not brag on his accomplishments; however, he has a reputation of having had great success with curing this misalignment problem after Model A owners had installed his "matched" set of his hand crafted metal timing gears accompanied by his "matching" hand crafted metal crank gears.

Most men are not even close to perfectionists ..... most men cannot even successfully cook fluffy white rice either .... don' t ask how I know.

Re: Timing gear teeth...??
 

Colin, If the main bearings are line bored a few thou different from the original position, the distance from camshaft centreline to crankshaft centreline will be different. Clearly once the bearings are bored, the distance doesn't change for the life of that rebuild. We take great care to get it right before starting the line borer. Measure twice, cut once!:D

Re: Timing gear teeth...??
 

Gear engineering is a very complicated subject.It is easy to get terminology mixed up when first learning it.
One thing that is seldom mentioned when discussing over or under size gears is how it is done. It is process called "generating up or down" as the case may be.
Here is a URL that will explain most of the terms.

https://en.wikipedia.org/wiki/List_o...re#Pitch_angle