Hi JimT,
As many know I hold many speed records on both new edition and vintage Whizzers [over 70 MPH]. Although the motors are very similar, speed parts for the vintage motors are "rare" because most simply restore the motor to original condition.
I have invested both time and large sums of money making parts for both versions of the Whizzer motor. I currently have 3 different hi-lift camshafts for the vintage motors, and 6 for the new edition motors in stock. I also had several Hi-compression "racing" heads in stock for the new edition motors.
To start with the three "C"s must be considered.....Compression, carburetor, and camshaft.
1. Mill the head .045" ~ .050" or replace with Hi-fin-Hi-compression head
2. Purchase hi-lift camshaft [version available for all Whizzer motors]
3. Increase carburetor size and match ports.
a. Also increase intake valve size.
b. Increase exhaust port size ["J" has more metal around port and can be opened more than "H" motor]
c. Port both intake and exhaust.
You can use an intake valve from the later Whizzer "300" series motors in the "H" or "J" cylinder. The "H" & "J" valve are 3/4", whereas the later valves are 7/8". Although you can also change to the larger exhaust valve the port size will restrict any advantage of a larger exhaust valve. In order to change to the larger valve the valve pocket must be opened up to match the larger valve, however this is easy to do as it requires using an end mill and re-sizing the hole.
The intake and exhaust ports are larger on the "J" than the "H", therefore the "J" cylinder is a better option for power upgrades. The best cylinder is from the later "300" and up series motors as both ports are much larger and the larger exhaust valve matches the larger exhaust port.
Please understand I have built some "H" motors [Jay Cruise] with massive valves, Cushman carburetor, modified hi-compression head, hi-lift camshaft [.192" lift], large ports and bored out to the max, but is so radical it is difficult to run at low speeds. The word "Sleeper" comes to mind when talking about Jay's motor, as it appears stock on the outside.
If you just want to double the power, go with the camshaft, port work, increase intake valve size, and mill the head. These upgrades will take your Whizzer easily past 50 MPH on the street. If you want to get closer to 60 MPH, simply make all the suggested changes and change head, increase carburetor size, and hold on.
Hope this information is helpful.
Have fun,
Quenton
