Let me start by saying that I am not good at engine tuning. I also may be expecting more than my 259 can deliver. Everything is new, fresh rebuilt 259 engine, Dave T-bow rebuilt WCFB and Mallory distributor, new wires, plugs, etc. Engine starts easy and idles and runs nice and smooth.
My current problem is coming off idle. It doesn't want to accelerate if I open the throttle quickly. It will stumble and backfire through the carb every time. I thought I may have a problem with timing or advance so I checked it all this morning. I will describe what I found in a lot of detail, because I am not sure if I am interpreting the factory spec's correctly.
I started by disconnecting the vacuum line from the carb and plugging it.
Warmed up the engine and set idle to 600 RPM.
Checked timing and it was right on the ignition mark. I understand that this means 4 deg advance. Timing light was showing 0 deg advance.
I accelerated the engine to 2500 RPM and measure timing again. To bring the IGN mark back to the pointer I had to adjust the timing light to 19 deg. Centtrifugal only advance is supposed to be 22-26 degrees according to the specs.
Here is my first question, Do I add the 19 degrees measured on the timing light to the initial 4 deg for an actual centrifugal advance of 23 deg which is within spec or was I supposed to read 22-26 degrees on the timing light
Next step was to check vacuum advance. I had a vac pump connected to the vacuum advance. Engine back at 600 rpm idle.
Up to about 9" vac I got 0 advance.
At 11" vac I had 4 deg advance on the timing light.
At 12" vac I had 11 deg advance on the timing light.
At 15" vac I had 15 deg advance on the timing light.
I stopped at 15 because that is the amount of vacuum I am getting at the intake manifold at 600 rpm
So the Vac advance numbers seem to be pretty close to spec without adding the initial 4 deg.
Once all that was done I adjusted the idle mixture to the best of my ability. Both screws ended up between 1 and 1.25 turns open.
Engine will still stumble and backfire if accelerated quickly.
Took it for a test drive and the performance is un-inspiring. I can mat the throttle, the OD will kick out and it will begin to accelerate but there is no set you back in your seat acceleration going on. Maybe the 259 is not capable of that type acceleration, I have no frame of reference for comparison. I would hate to get in a race with the wife's 130 Hp Hyundia Accent.
So, are my advance numbers ok or do I need to make some adjustments to the vac advance?
Am I expecting to much as far as engine power and performance for this stock 259?