Tach maybe prop question

link

Here, I fixed your statement for you 

An Innova 3568 is an example of a timing light with a tach function. A 5568 has a couple more features.

Or at a Harbor Freight near you, they sell a Zurich branded knock off of the Innova 5568 for a little less.

You'll be able to check/set your timing and check engine speed too.

You can find cheaper stuff, a lot of those won't have the tach function though so shop carefully.

So here are a few questions while you wait for the accountant to get back to you regarding the timing light route.  I only ask because of what I have learned on this site. How did it sound at WOT? Did it sputter, backfire, sound or act any different at WOT? Did it reach maximum RPMs before the throttle was at WOT or did it take WOT to get to the the 2300-2600 RPMs? Have you checked if the throttle at WOT is actually fully activating the carburetor throttle lever on the carburetor to wide open? Have the fuel filters/screens been cleaned and/or replaced? If not, I would make sure your fuel system, including clean fuel, is addressed. 

These are just a few questions that come to mind while waiting on the timing light decision, but again, I would stick to the problem solving path that has already been provided.

double check timing. make sure you are getting full advance out of the dizzy. and double check all your cable linkages and their range of motion. make sure those throttle plates are opening all the way. before doing anything else. sometimes its simple things like that which get overlooked.

What engine, what carburetor and what distributor does it have? are you working with all factory stuff?