The Ford Barn

Ron/IA · 08-13-2013, 12:18 PM

I recently obtained a Model A Engine block. It is bare with the exception of a crankshaft, camshaft, with gears installed.

There is no backlash between the crankshaft and camshaft timing gears. I am wondering if the camshaft gear is an oversize gear (my guess right now), but I have not been able to determine if it is. I am not finding any markings on said gear. Nor can I talk to the engine builder (he is deceased).

These oversize gears can be bought .003" and .005" over standard. My question is does anyone know the diameter of a standard camshaft gear? (Would this dimension be the overall diameter of the gear? I am guessing it is.)

Thanks,
Ron/IA

Pete · 08-13-2013, 02:04 PM

The oversize measurements are on the pitch diameter. Not the OD of the gear.
Dan McEachern can probably make you an undersize gear.

[email protected]
510-532-8228

PC/SR · 08-13-2013, 06:40 PM

I wonder if the fiber type gears swell with age and oil. A few years ago I put in a new fiber gear from Brattons, it fit with .003 clearance. Last winter I took it (and the cam) out to be replaced. The fiber gear had no play before I took it out. Just wondering. Any other similar experiences?

Ron/IA · 08-13-2013, 08:57 PM

Pete - Thank you for the information. Call me dumb, but is pitch diameter at the bottom of the teeth? I will try and contact Dan and see if I can pick his brain.

PC/SR - Interesting observation. I now wonder that too, because this engine was running before it was torn down. (I don't know how long it had been run, nor do I know why it was torn down to its present state.) Was the gear you put in a standard camshaft gear?

Thanks,
Ron/IA

Kurt in NJ · 08-13-2013, 09:24 PM

Have you checked it at several places by rotating the crankshaft to see if the backlash (or lack of it)is the same at all points of rotation

Perhaps if you could measure the distance between the crank and cam --
http://www.fordgarage.com/pages/camcrankposition.htm

Pete · 08-13-2013, 10:49 PM

Sponsored Links (Register now to hide all advertisements)

"is pitch diameter at the bottom of the teeth?"

No, it is approximately 2/3 of the way up from the bottom.
I won't go into the math on how a gear is generated but you can find it on Wiki.

larrys40 · 08-14-2013, 12:00 AM

Ron,
Usually the oversize gears have a ".003 or .005 stamped on them front or back.... if it's tight, my suggestion would be to try a new standard gear and see how it is.
You probably won't be able to accurately measure the difference... change the gear see where it's at.

Larry Shepard

PC/SR · 08-14-2013, 12:05 AM

Ron: I initially tried a standard gear from Dan McEachern but it was too loose. But that does not mean much for your situation because I also line bored and sleeved the cam journals along with a re-babbitt job so the relative crank/cam dimensions may well have changed by a couple of thousandths. I wound up with an .002 oversize cam gear from Dan.
Since your engine was running before, and if you are doing just regular driving, I would stay with that gear, or get a standard gear from the suppliers first and see how it fits. That is cheaper than getting a custom gear that may be wrong and would give you a starting dimension. Also check the teeth closely and see if there is any noticeable wear. Or see if you can borrow another one from a friend to check fitting.
Dan McEachern has standard and oversize gears in stock. I do not know if he has undersized, and I have never heard of anyone using one. But Dan is an artist and could probably make anything you want. As noted, your problem is finding a known starting dimension to work from. Good Luck with the project.

Ron/IA · 08-14-2013, 10:44 AM

All - Thank you for the information/advice. I now have several things to look at that I think will lead me to the right conclusion.

My first action will be to obtain a new standard camshaft gear from the club's spare-parts inventory to compare, and then go from there.

Ron/IA

H. L. Chauvin · 08-14-2013, 10:57 AM

Hi Ron,

Maybe now that the ,002" etc. is known to be applied to thicker gear teeth, your initial question may not be important now, but in response to your question in message #1 above:

"My question is does anyone know the diameter of a standard camshaft gear?"

Just measure a new standard fiber timing gear: Approximately 5-3/4" diameter.

08-13-2013, 02:04 PM	#2
Pete Senior Member Join Date: May 2010 Location: Wa. Posts: 5,409	Re: Std Camshaft Gear Diameter The oversize measurements are on the pitch diameter. Not the OD of the gear. Dan McEachern can probably make you an undersize gear. [email protected] 510-532-8228

08-13-2013, 06:40 PM	#3
PC/SR Senior Member Join Date: May 2010 Location: Santa Rosa, CA Posts: 1,279	Re: Std Camshaft Gear Diameter I wonder if the fiber type gears swell with age and oil. A few years ago I put in a new fiber gear from Brattons, it fit with .003 clearance. Last winter I took it (and the cam) out to be replaced. The fiber gear had no play before I took it out. Just wondering. Any other similar experiences?

08-13-2013, 08:57 PM	#4
Ron/IA Senior Member Join Date: May 2010 Location: Amana IA Posts: 527	Re: Std Camshaft Gear Diameter Pete - Thank you for the information. Call me dumb, but is pitch diameter at the bottom of the teeth? I will try and contact Dan and see if I can pick his brain. PC/SR - Interesting observation. I now wonder that too, because this engine was running before it was torn down. (I don't know how long it had been run, nor do I know why it was torn down to its present state.) Was the gear you put in a standard camshaft gear? Thanks, Ron/IA __________________ Ron/IA 1929 Fordor Steelback Hawk A Model A Ford Club http://hawkamodelaclub.org/

08-13-2013, 09:24 PM	#5
Kurt in NJ Senior Member Join Date: May 2010 Location: on the Littlefield Posts: 6,159	Re: Std Camshaft Gear Diameter Have you checked it at several places by rotating the crankshaft to see if the backlash (or lack of it)is the same at all points of rotation Perhaps if you could measure the distance between the crank and cam -- http://www.fordgarage.com/pages/camcrankposition.htm

08-13-2013, 10:49 PM	#6
Pete Senior Member Join Date: May 2010 Location: Wa. Posts: 5,409	Re: Std Camshaft Gear Diameter Sponsored Links (Register now to hide all advertisements) "is pitch diameter at the bottom of the teeth?" No, it is approximately 2/3 of the way up from the bottom. I won't go into the math on how a gear is generated but you can find it on Wiki.

08-13-2013, 12:18 PM	#1
Ron/IA Senior Member Join Date: May 2010 Location: Amana IA Posts: 527	Std Camshaft Gear Diameter I recently obtained a Model A Engine block. It is bare with the exception of a crankshaft, camshaft, with gears installed. There is no backlash between the crankshaft and camshaft timing gears. I am wondering if the camshaft gear is an oversize gear (my guess right now), but I have not been able to determine if it is. I am not finding any markings on said gear. Nor can I talk to the engine builder (he is deceased). These oversize gears can be bought .003" and .005" over standard. My question is does anyone know the diameter of a standard camshaft gear? (Would this dimension be the overall diameter of the gear? I am guessing it is.) Thanks, Ron/IA __________________ Ron/IA 1929 Fordor Steelback Hawk A Model A Ford Club http://hawkamodelaclub.org/

08-14-2013, 12:00 AM	#7
larrys40 Senior Member Join Date: May 2010 Location: St Charles , Missouri Posts: 1,998	Re: Std Camshaft Gear Diameter Ron, Usually the oversize gears have a ".003 or .005 stamped on them front or back.... if it's tight, my suggestion would be to try a new standard gear and see how it is. You probably won't be able to accurately measure the difference... change the gear see where it's at. Larry Shepard

08-14-2013, 12:05 AM	#8
PC/SR Senior Member Join Date: May 2010 Location: Santa Rosa, CA Posts: 1,279	Re: Std Camshaft Gear Diameter Ron: I initially tried a standard gear from Dan McEachern but it was too loose. But that does not mean much for your situation because I also line bored and sleeved the cam journals along with a re-babbitt job so the relative crank/cam dimensions may well have changed by a couple of thousandths. I wound up with an .002 oversize cam gear from Dan. Since your engine was running before, and if you are doing just regular driving, I would stay with that gear, or get a standard gear from the suppliers first and see how it fits. That is cheaper than getting a custom gear that may be wrong and would give you a starting dimension. Also check the teeth closely and see if there is any noticeable wear. Or see if you can borrow another one from a friend to check fitting. Dan McEachern has standard and oversize gears in stock. I do not know if he has undersized, and I have never heard of anyone using one. But Dan is an artist and could probably make anything you want. As noted, your problem is finding a known starting dimension to work from. Good Luck with the project.

08-14-2013, 10:44 AM	#9
Ron/IA Senior Member Join Date: May 2010 Location: Amana IA Posts: 527	Re: Std Camshaft Gear Diameter All - Thank you for the information/advice. I now have several things to look at that I think will lead me to the right conclusion. My first action will be to obtain a new standard camshaft gear from the club's spare-parts inventory to compare, and then go from there. Ron/IA __________________ Ron/IA 1929 Fordor Steelback Hawk A Model A Ford Club http://hawkamodelaclub.org/

08-14-2013, 10:57 AM	#10
H. L. Chauvin Senior Member Join Date: May 2010 Posts: 4,179	Re: Std Camshaft Gear Diameter Hi Ron, Maybe now that the ,002" etc. is known to be applied to thicker gear teeth, your initial question may not be important now, but in response to your question in message #1 above: "My question is does anyone know the diameter of a standard camshaft gear?" Just measure a new standard fiber timing gear: Approximately 5-3/4" diameter.