Glad I read this - I was looking at using a 670 SA to replace my Eddie 1406 since it also seems to be running out of steam in higher RPM’s on my mild 340.
Keep in mind that '670' has the same throttle bore and venturi sizes as a regular ol Holley 1850 '600.' Not sure how they claim it flow 670 cfm. Who knows... All I know is that it was a dog on my 340.
