I just bought a '57 with dual quads 245 hp engine (that runs a little rich) and 3 speed tranny.
The car has AC R43S spark plugs (installed by the previous owner) and the auto parts stores show that the right plug for this car is AC R45S.
I'm a little confused
Anybody have some advice?
Thanks in advance

 

Not sure what the owner's manual might specify but a R45S is two steps hotter than the R43S. I know my '73 says a R45TS and I use a R46TS because it burns cleaner w/ mostly in town driving.

I'd try the 45S and see how it looks after a few hundred miles.

 

Thanks for the advice 73shark!