I am in the process of reassembling an Old 403 that has been apart for 2+ years. Right now I am just trial fitting everything and checking clearances and the camshaft binds slightly. The motor is a complete rebuild with new cam bearings. And with no lifters or timing chain attached you can rotate the cam by hand with the cam sprocket, but it has a definite tight spot. I Chucked the cam up between centers on the lathe and measured .004" of runout on the #2 and #3 journals and .0025" on the #4 journal. I flipped the cam around in the centers to double check the measurement with the same results.

It is a hydraulic flat tappet cam from Comp. It was installed in the engine and ran in it for about 5000 miles before the motor cam apart for rebuild. The cam and original bearings didn't show any unusual wear at disassembly. And the cam just sat on the bench for the last 2 years.

Could the cam just settle to a .004" bend? And I have had a steel cam straightened before, but I assume that a cast cam would just snap under the force to staighten it.

Any suggestions?

You might try marking the high spot in the lathe, then setting it down on a reasonably flat workbench and hitting it on the high spot. Use a brass hammer or drift. See if a medium blow fixes it. If it does you're home free. If you need to hit it hard to straighten it you'll have to make up your mind if you're comfortable with how hard you hit it. You could also have it magnafluxed.

You could also pull it, look at the second bearing and srcape a little of the bearing where it shows signs of rubbing. I've seen some old-time builders get into extensive scaping of cam bearings on oddball old engines. Some of them used to run reamers through the cam bearings to get the cam in.

All this adds up to the end game: in non-racing engines cam bearings aren't very critical. You could probably just run it. See if the marked spot is on the top side, the pressure of the lifters will probably take care of it. It's amazing how soft stock cam bearings are, I've had some that I could mark with my fingernails. My fingernails are nothing to write home about either.

Tom

Thanks Tom. graemlins/thumbsup.gif

I am going to blue the cam tonight and put it in the motor and see where it hits. It really isn't much of a rotational drag when you rotate it by hand. I will see whet I can do.

I was over at Iskys many moons ago & I was watching this lady hitting a cam with a chisel & hammer(between the lobes) graemlins/clonk.gif .At the time,I didn't know anything about straightening cams!
BTW,she worked there.

I work for a shop that ran IHRA Pro Modified. And we had a motor granade one weekend and we had to have it running for the next weekend. The cam was bent like .035". And we didn't have a cam sitting on the shelf. So we put it in V blocks on the hyd. press and started working away on it. We got it staight and the new motor ran great with no problems with the cam. However this was a steel cam core not a cast iron one. It is pretty amazing how much abuse steel will take. graemlins/thumbsup.gif

.004 Total indicator reading is only off .002 from the center's.
Try a little assembly oil on the bearings.