Yep, I believe drilling the mounting holes a bit larger diameter solved that problem, it seems to me the threaded holes in the 273 and the 318 heads were at a slightly different angles. Opening up the holes on the intake allowed the bolts to be threaded into the heads and the slight difference in the angles didn't cause any sealing issues. But it was a long time ago.
Exactly right, that's how I put a Performer intake on my 65 273.
did the performer intake have the small ports ? what size did you drill the holes to ? did you use washers under the bolt heads ?
I don't recall the port match, I don't worry about it, it's turd polishing for a stock 273 in my opinion, lol.
I don't recall the size drill bit I used, wasn't much bigger than the stock opening as someone mentioned the intake bolts are smaller on the early 273 and there was almost enough clearance as it was, just did a test ft and inspection while it was on the stand.
I always use washers, so yes, but not so much because of anything specific to this swap.
