I went over to John's place three months ago. (this sentence should mean the speaker went over to john's place three months before now.)
- I had visited John's, three months ago.
Without a reference to another event in the past that happened after the speaker went over to john's place, can the second sentence stand? But, it would be grammatically accurate still, if it was followed by a sentence like "I had visited John's, three months ago. He was doing okay, but earlier in the morning he started showing signs of weakness. He looked sick now."
We use past perfects to describe events that happened before another event in the past. So, the highlighted part should be grammatically accurate, and it should convey the meaning correctly.
But, if the second sentence stood on its own it, would it mean three months in the past from now (the present)? Or would it be a vague sentence that suggests the speaker went over to john's place three months before some other event took place?