If your Nova is a inline six check the vacuum advance...You can watch it's action with the engine running and reving it up a bit..The external arm should move a little.. The vacuum line from the carb sometimes has a tee fitting operating both the vacuum advance and the vacuum modulator..If the vacuum advance has a ruptured diaphragm then the modulator doesn't get the correct vacuum..Man !!! how many times have I said Vacuum....Of course a good inspection of the line going to the tranny is needed..The hose on the modulator end rots and gets pin holes...I replace ALL the vacuum flex lines if they need it or not..Pin holes can cause all kinds of problems...A good replacement modulator has an adjustment for the rod it operates..Read the instructions...Do yourself a favor and stay away from SHUCKS and K-MART !!!!....Ever pulled the pan and changed the filter ????....If it has a cooler in the radiator it needs flushing once in a while....WARNING!!!..If the tranny fluid smells like it is burnt be careful about flushing with new oil..The new oils of today can wipe out the bands or clutches...It's time for an overhaul...And last but not least the throttle valve linkage (TV) has to be in place and correctly adjusted...Powerglides have got me around for many years........Al..