I second Mark's idea about the cat.  I experienced symptoms the same as
yours when the insides of a cat had broken loose and turned sideways.

Larry A.

On Wed, May 24, 2017 at 4:59 PM, John Rodgers <jrodgers113@gmail.com> wrote:

> Have a mysterious power loss on my new engine overhaul. It has run fine
> until two days ago. Now it won't pull your hat off your head.
>
> Engine runs fine. Starts easy, idle smoothly, runs smoothly at any rpm it
> is capable of turning. There is no spitting, missing or backfire. Just
> doesn't develop power to accelerate. Going up hill it just gets slower and
> slower and slower, the rpm will drop to about 1500. Top speef is about 55
> mph. I han't checked the timing yet, but thats next.
>
> Suggestions???
>
> John
>