<VV> engine rpm loss

[Michael Kovacs]

   Last weekend I was at the New York Safety Track. I was driving my '66 4d 140 PG. I had a problem getting the RPM above 4400 while locked in low. This was when I was starting on the long straight. The engine would respond quite well in low coming out of the 90 degree turn for the straight, but at 4200 the engine started to misfire and by 4400 it was clear that It would not rev any higher. 
 Looking back in the records, I haven't replaced the spark plugs R44F in over 10,000 miles, since I rebuilt the engine. DUH!   I recently installed 8MM wires and new cap with electronic ignition.   Are there any other suggestions as to a cure? What plugs now are recommended. (it is my daily transportation). 
 PS I now hold the track record for Improved Stock 1 
 PPS I was also the slowest car on the track. 
 Had a great time. Sorry you were not there ya missed a fine day. NYST was totally accommodating.Thanks NECC.