TheWitz (3/5/2021)
Thanks to all for your insights.
The cam is stock,
the valves have been adjusted by the shop a couple of times.
The shop did a compression test but
they did not give me the numbers. So based on the feedback I've received so far. The low vacuum is related to tuning and not because of the oversize pistons and head resurfacing.
These two statements would concern me. Not sure why the shop would have had to adjust the valves a couple of times - I assume this means the rocker arms? On a rebuild this is a once and done kind of thing - I wonder if your valves are not fully seating because the shop is "throwing darts in the dark" at the rocker arm lash. I am not sure how much money you spent on this rebuild but it would be frustrating to find that a shop is withholding key information such as the measurements from the compression test.
I would think that if you put this engine back under the hood yourself, you would not relish the idea of taking it back out and sending the engine back to the shop. Maybe you could remove the valve covers and check valve lash yourself just to be sure and rule that out as a possibility?
one last item - I know you mentioned that you had 15 inches of mercury on the vacuum gauge. Was that with a steady needle, a floating needle, or a bouncing needle? Maybe I missed that in the thread and all but it would be helpful in discovering your issue.
Daniel JessupLoveland, Ohio
aka "The Hot Rod Reverend"
check out the 1955 Ford Fairlane build at www.hotrodreverend.com