[halfton]

when using a msd 6al box on a 355 with aluminum heads and 9.5 to 1 comp what should the plugs be gapped at using regular 87 to 92 octane pump gas

 

[veno]

start @ .035 you may find that depending on many factors(chamber shape, compression, etc...) gaps from anywhere from .030 to .045

 

[The Big Al]

per MSD:

Spark Plugs: Choosing the correct spark plug design and heat range is important when trying to get the best performance possible. Since there are so many engine combinations and manufacturers, MSD does not recommend which plug or gap is exactly right for your application.
It is recommended to follow the engine builder or manufacturer's specification for spark plugs. With that, you can then experiment with the plug gap to obtain the best performance. The gap of the plugs can be opened in 0.005" increments, then tested until the best performance is obtained.


I have mine at .038

Al