[Barry_R]

1.710 exhausts in an Edelbrock head will scrub on a 4.070 bore. I've done it and had to fix it. Took the same measurement as above - they physically clear, but flex and movement in operation puts them into contact.

They will also work fine on a .030 over (4.160) 428 bore. I've done that and had that one on the dyno and apart for service and inspection. No sign of contact. I've never tried on a standard bore 428 - did not think many of those existed anymore....