[Cal Metal]

347:

The 44mm venturi could be a little larger for your 347 cid but it really should pull 6,000 with a 44mm venturi. The 347 equates to around 600cc per cylinder which means you need to be at 44mm minimum if you want to achieve your desired RPM. I have a chart that I can post to show what I mean.

Before you do that, however, check the size of your air correction jet. If it is too large (200-210 or beyond) that can be a problem, as it will limit your top end RPM. It is a cheap, easy fix. I would try that first if the other variables (cam, heads) are within range.

Also make sure the aux. venturi is not necked down to, say, 34mm. 37mm. would be more applicable.