AC B Cam gear timing mark (older vs newer)

I have a 1953 B that is in process of being restored after sitting uncovered for years. As a result the cam was pitted beyond use. I acquired a good cam with gear that looks better than the original, less pitting on gear teeth. My question is that the two gears have timing marks in different places. I understand that the older gears had two straight marks versus a line and a circle on the later gears, but this older gear has the straight lines offset from where the marks are on the newer gear as well as punch marks offset from the lines. One punch at the governor mark, but offset one tooth from the same tooth as the newer gear based on the shaft key position (black circle in picture). There are two punch marks at the crankshaft timing mark in between the gear line mark and same space as the newer gear based on shaft key position (black line in picture). I could understand it if the factory marks were in the wrong position and someone punched new locations, but the punch marks are not offset in the same direction, one is offset CW and the other CCW. Any help explaining this would be appreciated.

Tony
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Being a 53, is your governor mounted on a magneto drive gear, or is it part of a distributor drive shaft assembly? If you have an OEM dist. drive, you can forget about timing the governor gear, and concentrate on the cam/crank timing. I can't picture what you're describing, and I probably can't adequately describe what I'm thinking. When the cam is timed correctly to the crank on #1 @TDC, as I recall, both cam lobes should be symmetrically away from the lifters.

I posted this down below but here it is again. This shows the timing for that engine. The drive for the magneto needs to the horizontal (cross ways) not up and down or on an angle either way.
The straight marks will line up when the gears are meshed.

Punch marks-- I was taught back in the late 1950's to punch mark any timed gear where it set when I removed it by an older mechanic. I did this for years but have not for more years (when I find factory marks). This could be the reason for punch marks. I have never seen punch marks on any of the B's and C's that I have taken apart. I have never heard of a factory miss mark either. If you go with the factory marks you will be fine.

(quoted from post at 14:43:42 01/13/17) Being a 53, is your governor mounted on a magneto drive gear, or is it part of a distributor drive shaft assembly? If you have an OEM dist. drive, you can forget about timing the governor gear, and concentrate on the cam/crank timing. I can't picture what you're describing, and I probably can't adequately describe what I'm thinking. When the cam is timed correctly to the crank on #1 @TDC, as I recall, both cam lobes should be symmetrically away from the lifters.

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Yes, governor is on magneto drive gear. My main concern is having the cam timed correctly to crank. If I'm thinking right, with 46 teeth on cam gear one tooth would be ~8 degrees off. Unless I can find some reason not to, I'm probably going to use the teeth that match the original gear teeth counted from the shaft keyway. I just hate to do something without understanding the why. I wish I could get the picture to load, that would help.

I guess you can not go back and add to a post in then board. When you have a distributor the governor gear may mot be marked as the drive can set in any angle. It can be timed by changing the distributor rotor to point in the number one position by lifting the distributor up and re setting it. However I like to set the drive as pictured anyway in case a magneto would want to be used some time in the future.

Thanks Dick. I have seen that picture before and agree with what you say, but my problem is that I have two cam gears that if stacked together with the keyways lined up have the timing marks at different spots around the gears. If I just align to the factory marks, the replacement gear is going to be timed different than the original gear. I was able to get a picture of the older replacement gear in question uploaded in the last post so hopefully this help explain what I'm talking about. The picture attached to this post is the original gear with O and | marks.

Tony

The factory mark at the bottom of your picture is on the female tooth. The crankshaft will have the factory mark on the male tooth. That is the way it goes if you have a camshaft from a C, B, CA, or RC. Looking into the camshaft it looks as though it might be a camshaft from a D 14, 12, or 10. Make sure the spring does not slide way back in the center of the camshaft. Also check to make sure the camshaft has the little holes for the oil to spray out onto the rods. It might just be the camera angle. The punch mark is not factory!

The camshaft is timed the same on the D 14 type as the B's but you get no oil to the rods with it.

Where did you get the replacement gear? I probly have a dozen camshafts out here from a span of years and they are all the same.

I just went out to the shed and picked up a couple camshafts with gears and no part numbers on either one. I didn't look any farther. Kinda dark and my walker would fit thru to see more. These were setting in front of the wash tank and have been there for over a year. The were shinny when I set them down. They have surface rust and I wire wheeled the front of the gear.

Your gear does not go with the B engines. I suppose if you remark it and it meshes properly it will work.

If the gear and camshaft came together the camshaft would most likely be wrong as well. Check it for the oil holes.

Oh Wow!! Didn't mean to make go out with a walker to check on something but I appreciate your help. Camshaft and gear were together and came from a tractor that was parted out and was labeled as an AC B. Both camshafts have the same numbers 206973 and both have the oil holes. Only difference I can see is the original one has oil grooves around the bearing journals, like the one you show and the replacement one does not. Original gear number is AM-2926-5, replacement is AM-2926-3.
I figured out what the difference is based on this text from the AC B service manual. The newer one has a | and O mark with the crankshaft mating with the | mark closest to the keyway and the older gear is the one with two | marks and the crankshaft mates with the | mark opposite the keyway. In other words the cam is rotated 180 degrees when timed with an older gear versus a newer gear. When the newer cam gear is timed as described in the service manual the engine is TDC Compression. When an older gear is timed as described in the manual the engine is TDC exhaust. So either way the results are the same.

Oops, that didn't work too good. Let me try to get the service manual text again.

It has been a while when a problem would cause me to go take pictures in the cold. This still has me scratching my head. I doubt I will ever be taking on any new engine projects to see what you found. It will be in my memory bank until the bottom rusts out more and I get a larger leak. I enjoyed this!

Dick, I have been puzzling over this as I read the exchanges. I too wondered about possible newer, D series engine differences.

Another idea just popped up. I had an early B I fixed up. It had no hyd. pump, nor elec. system, nor any provision for either. It had a one piece, cast iron belt pulley, and the shaft size was smaller than later B's. No temp. gauge nor thermostat, and a non pressurized radiator. As I recall it was the first year production after the original Waukesha engine was replaced. There were a couple of crude anomalies I encountered. One was, where the fuel tank mount bracket bolted to the torque tube, the surface was cast, and never machined, and it was not level. In order to level the bracket, and therefore the tank, and hood, I had to space up one side of it, with maybe two 1/2" flat washers.

The other was even more bizarre. There was an odd assortment of washers under the rocker shaft standards when I disassembled the head. When I tried to reassemble it without, I couldn't get enough throw on the rockers without them colliding with the edge of the spring keeper area. I removed the head, measured valves, etc. and questioned the shop who had rebuilt the head. Everything was perfect. I finally acquired a bunch of fender washers, and mic'd them to get ones the same, and placed a couple under each standard.

I see the one picture if a gear here is very rough. Cast, but no machining on the sides. Now I'm wondering if that was first year production, and a little different, with markings and such.

His first gear that was rough and was being replaced is marked like all that I have or used. The one he got to replace it was the one that was marked different. 180? from normal. I have two 1938 running B's here that I rebuilt the engines on and they are marked the same as any B's, C's or CA's that I have rebuilt. I never heard of marking timing gears that was marked on the TDC exhaust stroke when assembled. I see it in his pictures so it is that way. I wonder how many more would be around like that. I am glad I was able to know at least one is that way and would like to know if anyone else has a gear marked the same.

On your rocker arms I would not know what was going on, I would guess someone substituted different rocker stands. I bought several rocker arm assemblies off Ebay as well as all the ones from parts tractors I bought and rebuilt several for other people and the stands were all the same height. The heads I rebuilt and removed .150 off the face needed .150 shims under the rocker stands. I have two types of stands out here but both measure the same. One type is stamped and welded and the other is cast pot metal. I don't like to reuse the pot metal stands.

Thanks Dick,

I unlike you, am just beginning my experience with vintage tractors and figuring out the quirks of these engines, but it bugged my why the marks were so different on the two gears. Last night i took the older gear and added marks that matched those on the newer gear. I stuck the crank and cam in the block and timed the marks with cylinder one TDC. No matter which set of marks were lined up the other set was lined up after turning the crank 1 revolution. So it's just the way the gears were marked for different years. I'm waiting on the rebuild kit so it will be a while before I can see if I am right in my thinking.
Thanks for passing on some of your knowledge to help those just starting.

I hadn't thought of that. Perhaps on some earlier rebuild, a lot was shaved off the head.

Dick, I have read with great interest some of your other posts about shimming bearings and filling bearings. I got my rebuild set in and am starting to check the main bearings. I have no history with how this engine ran before teardown. Engine was stuck from rain down exhaust. Crankshaft was ground -0.020, with new -0.020 bearings. I have verified the cranks journals for size, roundness and taper and all looks good. 0.010 shims being used since block was not line bored. I have not checked the bore alignment with a machined edge yet. Bearing 3 seems to be working fine. 0.002 plastigage oil clearance with 0.010 shim, torqued to 80, crank turns freely. If I loosen one cap bolt, a 0.003 feeler gage will slip between the cap and shim to check crush. Bearings 1 and 2 show 0.002, 0.003 plastigage clearance when torqued but crank is too tight to turn. Loosening one cap bolt a 0.006 feeler will slip between cap and shim. If I reduce this gap to 0.003 by slightly tightening cap bolt to effectively create the same crush as #1 the crank turns free. This suggests to me that I need to file the bearing shells to reduce the crush, but I would not expect to need to do this with new -0.020 bearings and a -0.020 ground crank. I just want to make sure I understand what is going on and make sure I make the right move.