I have a moderately built Pontiac 400 in my '72 GP. Moderate cam, edelbrock RPM intake, rebuilt rochester 4bbl, stock exhaust manifolds. All that work was done 18 years ago. When the motor revs up higher in the rev range the power drop off really bad. It happens at around 4250rpms and it will stop revving at 5300. Im think that it have worn out valve springs. Any suggestions?
18 years ago is a long time, are you still using points and 18 year old plug wires? If so, I would put in new points, plug wires, coil wire and plugs for that alone will stop a motor from revving in the upper RPM range. Your valve springs could also be a contributor if the car was sitting up all those years. I would change the easy stuff first, then take one step at a time, tuning, timing, etc...
+1 76TranzIn addition did the car run well 18 years ago? If so your problems are more than likely just do to time. Check your centrifugal advance, make sure its clean and functioning properly, also the vacuum advance. Like 76Tranz said give er a tune up, points to plugs and time it. if that don't do it then go deeper. Let us know how you make out.
Poncho huggen gear snatchen posi piro.
secondaries might not be opening.