Which spark plus to use with Perma-Tune?

[Bruno911]

My 77 911 2.7S has a Perma-Tune spark ignition box. Does anyone know which spark plugs to use? Underneath the model.

[T77911S]

bosch copper plugs. (W5...)

i would really consider replacing that with either an MSD unit or the original bosch unit.
(and coil)

[Bob Kontak]

Don't gap the plugs to sixty thousandths of an inch because you read where that will work.

Keep the gap much closer to stock.

Also, on the Permatune box............. What T77911S says. Replacing the P Tune is good insurance you will not be stranded. It's a roll of the dice if you keep it on - and it may go forever - some do, many don't.

[Joe Bob]

They don't call them PermaCrap for nothing.

Use the cheap, copper plugs...you can find 3 or 6 pin rebuilt Bosch units for 3-400.

[T77911S]

if the W5 fouls on you, go with a W7

[manbridge 74]

I believe the factory used Perma-Tune in the mid 70s...

Permatune 3 Pin box , factory in 1975

Older boxes are apparently robust and repairable.