Firing order old school tip. 7 and 8 must not be parallel to each other. They may only cross each other one time and be kept as far apart from each other as possible from distributor to plugs. You said hearing left side may have spark happening at strange time. Another thought is spark scatter with the higher RPM you mention. Stock distributor with Pertronix is still an old housing with shaft, bushings etc. possibly out of spec. Dyno runs of my old stock dist. with Pertronix gave spark scatter. New distributor no more concern. MSD in now, DUI Ford Duraspark owned too for the close as stock look with stellar performance. Full length bronze oil impregnated bushing gave me the reason to go with this unit. Black cap with request available.
The Ford Duraspark we offer is a high performance unit for those who want a completely stock appearing or factory style electronic distributor. Each Duraspark Electronic Distributor is custom calibrated on a distributor machine and blueprinted for your Ford engine to provide maximum power, torque and instant throttle response. We tune the centrifugal advance using information about the vehicle and engine such as cam duration & lift, carburetor size, compression ratio, vehicle weight and octane of fuel. A super smooth advance curve assures excellent performance and mileage. The vacuum advance is calibrated for maximum fuel economy and light throttle ping is eliminated. The factory center bushing on our Duraspark Distributors is replaced with a full length bronze oil impregnated bushing to provide increased durability and cure top end timing fluctuation, which is a common problem in these distributors due to the weaker stock bushing. Our Duraspark Distributor can be used for a number of applications from everyday street use to all out racing. The distributor is capable of 10,000 rpms with our Dyna-Module and Inferno Coil kit. It will work with other modules and coils, but rpm ability is not guaranteed. Comes with a brass terminal cap and rotor in your choice of blue or red.
Sorry for the long post. DW
1969 Ford Mustang GT 428 CJ 4 speed hardtop. Since 1980 owner, technician, driver.