True to form it's the cam. So much for a quicky.
What about the donor motor in the bed?
Previous owner hit the interstate and didn't check the oil, roached the motor. Came with a donor motor.
1) Is this Plan B? If the donor motor's cam & lifters pass a visual inspection are you going to button it back up
and swap this in?
2) Or, if the donor motor looks promising, are you considering a quick refresh of the normal short block
wear items (rings, bearings, new timing set, gaskets) and then swap it in?
3) Or, if the donor motor looks promising, would you use this as an excuse to refresh the heads along
with the short block stuff in scenario #2? Then swap it in?
****
Worst case scenario is that the donor motor is also wounded just like the original one. This would mean that
both engines have been polluted by really hard chewed up lifter/cam lobe bits throughout. (And also the
engine oil cooler if equipped!) :-(
NOTE: For all the trouble that EFI systems can give us in troubleshooting mode, one of *the* main benefits
that they give us engine guys is that since they are much more precise with cold fueling (vs carbs with
the mechanical choke plates) ...you can open up a high mileage EFI SBC and there's near-zero ridge at
the top of the cylinder bores? And I've personally seen decent cross-hatch still showing in the bores?
It's amazing, especially when compared to what an old carb guy is used to seeing when the heads come
off a carbureted junkyard jewel. :0)
In English, as long as you open up a high mileage EFI SBC *before* a cam failure, it's possible to give
the engine a quick hone, clean up all the bits, install new rings, bearings, timing chain set, and fresh
gaskets, and have a nice, quiet runner with a long life on short money.
Let us know what you have to work with & what you are considering...