Cam lobe going flat...what now?

If you take the rockers and pushrods out, you can reach down with a hooked piece of wire, (welding rod) flattened at the end, and snag the lifter C-ring groove where the end-gap of the c-clip is, if it's a fresh lifter, it'll pull right out, and you can use a magnet to pull the lifter up thru the gap between the head and intake, (may require loosening one intake bolt that protrudes).

You will then be able to determine if the lifter's collapsed, or by looking at the bottom of the lifter for signs of wear..

You then may be able to inspect the lobe thru the lifter bore, and if it looks good, slide a new lifter in, and cross your fingers..

This method works for replacing a noisy lifter without taking the manifold off.

If the lifter is fresh, but difficult/unable to remove, may indicate bottom of lifter damage, or on older engines, shellac build-up below lifter bore.

hope it helps