Hi Everyone

As some of you know, I have just pulled apart the engine from my 1955 A/C B. I have an issue that I could use some guidance with. I am a machinist by trade so I tend to measure parts as I go. As I went to pull the camshaft out , I gave it a bit of a wiggle to see if there was any movement between the camshaft and the front bearing. I saw some side to side movement. The camshaft journals that ride the bearing are 1.749. That seemed acceptable . The front cam bearing inside diameter was 1.758 - 1.760. So the front cam bearing is out of round slightly by .009 - .011 and larger than the cam. That seemed a bit excessive to me so I purchased new cam bearings. I received the bearings yesterday and got the telescope gauges out and to my surprise, the inside diameter of the new bearings were .009 larger than the camshaft or 1.758.

From other Allis owners that I have spoken to, Those bearings over time tend to ware their inside diameter, which in turn causes low oil pressure. I checked the numbers on the box and they check out. In my honest opinion, you would think that they would have closed up that tolerance a little bit. Any input on this would be appreciated.

Thanks

I am off to post another topic.    

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read the last paragraph........

Thank you for the response Tom.

That dawned on me last night, I checked the outside and the inside diameters on the new bearings with a micrometer and a telescope gauge. The inside and outside diameters were the oversize the same amount. They were each .008 oversize . When the bearings are installed there has to be certain amount of interference fit. So when they are pressed in, the diameters (inside and outside) should fall into tolerance. :) I will post my progress. Thanks and best to everyone.

Something tells me that my new bearings are going to be okay.

Update: I made a stepped washer with a half inch hole in the center The diameters of the washer were roughly .015 under the outside diameter and .010 under the inside diameter of the bearing, so it was able to place it into the old bearing and not effect the bore in the block as it pulled through while remaining on center. The three bearings came right out.

As much as I wanted to install at least one of the new cam bearings to measure the inside diameter and put an answer to my original question, I didn't install it. I kept looking at the block and thought that it might be best to pull the piston sleeves and clean the block inside and out before installing anything new to avoid any contamination.  It may be a few days until the next update.

Steve (Maine) 

I will clean the oil path tomorrow night and install a bearing. Then we will know for sure what the final diameter ends up being. The cam shaft measures 1.749. So the cam shaft is within spec. The tolerance between the bearing and the shaft is .002 - .004. If it is any larger, the new cam bearings were manufactured oversize and I will probably be out of luck in returning an installed bearing.

I just put an end to all of this. I am returning these bearings. I did not pay a lot for them. Maybe that's why they are out of round and oversize. I just ordered some real camshaft bearings

Thanks for your patients with me. I am not inexperienced, I am only a first timer with this type of engine.

Steve (Maine)

Yes, It had the hole in the bearing. After got the first one in, I said to myself, I wonder how many people get these holes to line up? Clearly, I didn't. I got half a hole. My first thought was I could use a long 1/4 inch drill and open the hole. That idea lasted about 5 seconds. I knew that I would just rip the bearing apart or break the end of my drill bit. I used a #3 center drill 4 inches long. I went through the hole in the main bearing to the cam bearing. I touched the cam bearing with the tip of the center dill and slowly went through. Now there is a straight shot hole to the bearing. Because of the way the drill is designed it did not grab the cam bearing. It only created a slight burr. It was nothing compared to the burr that the standard 1/4 drill would have left. I removed the burr with a 3 sided burr knife.

 

 

This is my mini mill.