Engine surge at highway speeds

[Missing Link]

I have been messing around with this here flathead (59A) for a while now. I run two 97's that I believe I have dialed in pretty well and I am running the stock distributor. I messed with the vacuum brake a few times as I had a pinging situation. It seems that I have fixed that problem and now onto the next. Trying to get it running nice and capable of comfortably handling highway speeds. Well, when I get this thing rolling about 50-55mph I get a surge periodically. Anything above 60mph surges extremely bad. It's quite irritating actually. The car runs great at any speed below cruising and the surge isn't a miss, it's more like a chugging situation. I have the timing set in to about 4 degrees btdc. The last few weeks have been mayhem and I think my brain is fried. I am probably missing something obvious so any suggestions on what to check out next would be appreciated.

[DrJ]

almost every time that's happened to me it was the plug wires.

[Petejoe]

Had this problem on my 37 in the past and even of late.
Changed the fuel filter, tightened up and checked for vacuum leaks, Even rebuilt the carbs. Last year the issue was a simple solution. The dual holley linkage was giving me this problem. The simple solution was to attach a spring onto the linkage preventing surge from my foot giving it gas in spurts from the road vibration,
If your engine is running well up Up to that point. I would check this out.
This year went through the same old steps again. Didn't take care of it.
Only to find a few of the plugs fouled causing a miss.
Flatheads sure are tempermental. A new set of of NKG's and I off to hotrodland.

[Bruce Lancaster]

Gentle surging is often caused by a lean condition--try slowly pulling out the choke (attach baling wire to the choke levers if you don't have formal arrangements...) and see if conditions improve. If conditions improve and then drop dead, cause was insufficient fuel flow--if things stay improved as long as choke is partially on, we then need to find actual cause of leanness.

[Missing Link]

Thanks for the input so far guys. A few more areas for me to look into.
I can say that since I put on new water pumps the car runs much better. That seems like an odd combo, but the passenger side pump was leaking and tossing anti freeze all over the place including the distributor. Now that it experiences a dry condition it seems to run better. Makes sense now, huh? http://www.jalopyjournal.com/ubbthreads/images/graemlins/smile.gif I may be dumb but I'm not stupid. http://www.jalopyjournal.com/ubbthreads/images/graemlins/crazy.gif
A few more things; the carbs were just rebuilt last year and it took me a while to get to a nice idle mixture...they seemed to be running rich but maybe I leaned them out too much. Hmmm, that has me thinking some more...the throttle response isn't as good as it used to be either. Maybe it is starving...and the plugs are Chumpions which I have never liked to begin with and still don't know why I put them in. New non-champion plugs on the way for sure.
Keep the info coming guys. Thanks again.