ford 351 older 1984 Nautique

After I get over 4000 RPM's she begins to lunge, if I pull back the throttle, all is well. Actually everything is fine but the very top end... it seems like timing, but how do you time at top end? I timed with a gun at low RPM, stablized and runs great.. but at the higher end, I am not sure why it is still off.

Any clues?

By "lunge", do you mean bogs down quickly and looses power intermittently(sp) until you pull back on the throttle? If that's the case, my 1970 Mustang always does this as soon as my fuel filter fills up with the miniscule debri from the old fuel tank I've failed to replace / repair. The fuel flow is insufficient for higher rpm, as it's fine until somewhere in that rpm neighborhood you mentioned, but a quick filter clean and I'm back in business.
-Reid

You can plot a "Timing" curve for the higher RPM's if you still want to dig into that. Typically, you plug the vacuum advance and set timing at idle. Then hook-up the advance and run up the RPM's and record again. You can do this every 500 RPM till your satisfied. The timing should continue to change, albeit in smaller increments as RPM increases.

I'm not familiar or know of any adjustable vacuum advance, but the MSD's mechanical advance can be adjusted...typically for high compression racing appliactions. You change springs for different curves. I read where a high compression engine will advance quickly and max out at 2500 RPM, whereas a street machine with vacuum advance will continue to advance up to 4500 RPM???

Unless you've changed compression you'll be OK, but this exercise will allow you to see if you are not getting proper advance at higher RPM's.

also i forgot to have you check you pickup in the tank for a plugged screen. the screen sometimes are hidden up inside of the tube and you have to dissassemble the tube to find them.

I assumed when you said Older you had a vacuum advance like both my older boats. I even see there's an old CC on E-Bay with vacuum advance. Sorry if that doesn't apply to your motor.

The timing plot's the same concept independent of Advance Mechanism. The SBF's like at 30-35 degrees total advance.