QUESTIONS AND ANSWERS ABOUT TWIN-PLUGGING A 356.

Why two sparkplugs?

The 356 has a large hemi-type combustion chamber with the sparkplug located on one side. The fuel charge ignites at the sparkplug and has to travel across the entire chamber to fire completely. This requires a lot of ignition advance which can lead to detonation. Firing two plugs provides two flame-fronts that burn the mixture more efficiently from two directions.

Does less advance provide more power?

Less advance by itself doesn't provide more power. The more complete burning of the mixture and the higher compression ration provide the boost in power. Less advance required at the power peak is just an indication that the two plugs are doing what we want them to do.

How high of a compression ratio can be used with the W/R Twin-Plug Ignition Kit?

We have used a 10.8:1 CR with EFI. With carburetors 10.5:1 is recommended with the High Lift 288 cam.

Do I need to use a CDI ignition?

Capacitive Discharge Ignition provides a much hotter spark that will meet the needs of a high compression, high rpm engine. Fouled plugs are a thing of the past.  Porsche has used CDI ignition since 1969.

Can I use heater boxes with twin-plugs?

The factory heater boxes can be used but will need to be modified.  On double-flapper boxes the bottom flapper has to be fixed into place.

How do I raise my compression ration?

We can supply a piston and cylinder kit for twin plug in either 86.5mm or 91.0mm with a 10.8:1 compression ratio.

Further questions please call John at (562) 439-3333 or mailto:john@willhoitautorestoration.com