Tweety Bird said:
The bolt doesn't take any torque when the engine is running; that is, the cam isn't relying on the bolt to make it turn.
The bolt and washer simply hold the cam sprocket in place against the front face of the camshaft. The locating dowel and the friction between the sprocket and cam are what provide the torque to the cam. And since the bolt head is smaller than the hole in the sprocket, you had nothing securing the sprocket to the camshaft.
I "thought", but I could be wrong, its the opposite. The locating dowel is just that, locate the cam sprocket on the cam face with the correct timing. The clamping force from the nut and washer clamping the two together, actually bears the torque load of turning the cam, that the dowel itself would shear off at any higher rpm or stress.
I know for a fact that is true for some later engines, I might be total wrong for the earlier B/RB engines. Regardless, I think everyone agrees that its a miracle that dowel didn't shear off, and the correct thing to fix it is to get a "proper washer" and torque it to spec.
I would NOT use any old bolt and washer from the hardware store, I would get the specific bolt and washer for the engine, in fact this is what a google search turned up.
http://store.440source.com/Bolt-kit-Timing-Chain-to-Camshaft-Single-bolt/productinfo/109-1510/
These have been long discontinued by Chrysler, and we couldn't find them anywhere, so we reproduced the unique washer and sourced the bolt in a super strong grade 8 version. These fit all years and all engines with single bolt sprocket. Will not work with 3 bolt cams.
Hmmmm, so is it possible the original rebuilder couldn't find the specific washer and used some generic washer from the hardware store to cause this?
--------------------------------------------------------------------------------------------------------------------------------
On a related note, the latest API/SAE spec (SN) for motor oil, has dropped EP zinc additives for high impact wear resistance. This is because all the motors of last 20 years all have roller cams in them and the zinc in the oil shortens the life of O2 sensors and Catalytic Converters. Tappet/Lifter Cams need the EP Zinc additive for the metal to metal impact and wear.
What I've read, if the cam is already broken in, the lack of zinc won't increase the wear to much to cause problems. But if the cam is brand new, using the latest API/SAE spec oil will result in the cam wiping tappet/lifter and cam lobe faces right off.
Some of the "High Mileage" versions of popular brands of oil have the API/SAE (SM) standard, (you want to look it up, I'm pulling the standard designations from memory, so I could be wrong), and thus have the zinc for tappet/lifter cams. You can also buy zinc additives to pure into the engine after an oil change as well.
BUT, this is just info for the future, you've already stated the cam is moving fine and the problem was NOT the cam seizing up, but the bolt washer coming apart, so it wasn't the oil that caused your problem.