Hi Turbo317-
Hopefully this will get the party started...
I ain't the valve train expert, but I am always wary when I have a valvetrain failure of any sort - and I have had my share of destroyed cams, valves, and pistons.
The question is like Clint said: "Do you feel lucky...?"
The fact that the pushrod is under the manifold means there was a bad enough problem with the rocker arm and/or spring to let it fly.
I know for sure that the tappet is bouncing around on the cam like a BB in a box car...could be some or all of the noise.
There may be mixed opinions on cam bearing replacement. Maybe someone who has more expertise than I will chime in, but I have not had any problems with a new cam and original bearings (on a well-maintained engine)...just be VERY careful with removal and install so none get nicked.
On the other hand, if you think the engine has too many miles and/or has been abused or badly maintained, might as well go for new cam bearings plus the following:
At the very least, even without new cam bearings, I would replace cam, lifters, rockers, and pushrods with new, and check pressure on all the springs. I know this can be pricey, but that is the way I would go.
Other than my approach, remembering that the cam is the "general" of an engine...
1. One or six new lifters will wear cam lobes faster than the original lifter(s) would. A used lifter from some other engine...fuhgedaboudit. Short term - might work. But a bad long term solution that is really risky.
2. Re-using old lifter. If it is not collapsed, I don't like the idea that it has been bouncing around on the cam...especially without pressured oiling. If you try to fix or re-use it, risk is still there.
If it is collapsed, it could have caused bad pushrod to rocker arm and valve geometry (see 3 - 5 below). If it collapsed and was rebuilt...I suppose it could work...maybe some more experienced members can opine on this.
3. Re-using old push rod. I wouldn't.
4. What is the condition of the spring? I blew an engine once when a spring failed. Even if its compression is within spec, how do you know it was not structurally tweaked when the pushrod went out? I would replace it with one that has the same spec. as the others (assuming yours is a stock engine...sorry, I do not know the spec).
5. Finally, regardless of how much you decide to do, be VERY sure that the valve stem is not bent at all!
Please let us know what happens.
Steve
