My 1970 v8 has only done 200 miles since having a new cam, timing gear, followers and push rods. After running in the cam, All has been well until recently when I’ve been getting a tapping noise that increases with engine revs. This occurs when the engine is warm and lasts for a minute or so before disappearing. If I continue driving, it tends to return a few minutes later but then clears again. The rocker shafts are fitted the correct way and there’s good oil flow at the top. It’s also had a crank regrind and shells and has great oil pressure. I have however noticed a little wear on around half of the push rods and it appears that they are touching their guide holes in the block. Could this create the tapping or have I got a duff follower? I’m using comma x flow 20w 50 oil