Engine sputtering at about 65

Dave Haertel said
This happens with a moderate acceleration, if I slowly try and increase it, there's pretty much no response, I have to ask for it moderately to get a response and the response is the sputtering.

Sounds like this is having problems when the power valve on the primary side is trying to open or when the vacuum secondaries are supposed to be opening. Since we don't know if you have a vacuum or manual secondary carb, it is a bit hard to diagnose. Can you post a pix of both sides of the carb? Or find the Holley list number on the carb and post that?

One very informative way to help diagnose this with the vacuum gauge is to just run a long vacuum line into the passenger compartment and observe the vacuum readings at various problem stages. If you are running on flat land at about 55-60 mph I would expect a vacuum reading of 11-13 inches with that type of idle vacuum reading. Then a moderate acceleration would give a vacuum reading of 5-8 inches, where the power valve would be opening. Pushing further open will drop you down lower in vacuum reading. Having the vacuum levels at various operating conditions tells us what the carb is trying to do.

If you have not set up the timing, you need to do that first. Get it up to around 10 degrees initial advance for starters. (Vacuum line disconnected from the distributor end and plugged.) Once this is observed, then reve up the engine slowly to about 3000 RPM and watch the timing, it ought to advance as you rev it up to the mlow-mid 30's range if the initial timing is at 10 degrees. That may not be the ultimate best point but it will get you to where the timing is not an issue and not so advance as to where you need to mess inside the distributor; at this point, you're just getting it in a happy range to make sure that is not messing with things.