Originally Posted by Brian Carlton

Since you know the stretch, the spec for the IP timing should be adjusted to compensate for the stretch. IMHO, about 1/2 the stretch should be added, or subtracted from the spec (depending on which method you are using).

For example, if the stretch is 4 degrees and you use the RIV tool, the setting would be 13 ATDC. The normal spec is 15 ATDC and you advance the timing by one-half of the stretch.

The amount to adjust (1/2 the stretch) is just an estimate presuming that the IP is 1/2 way up to the camshaft. In reality, it's probably closer than 1/2 way.