Toronado.org

So i recently swapped out the plugs in my 1966 toronado 425.

the parts place said it took R43s. When i pulled the plugs, they were 45S. I compared the two and the 45S plugs were longer my alittle. The parts place said someone put the wrong plugs int he car the last time they were changed as the catalog calls for R43S.

I looked on the interweb and found conflicting data. Seems that some places say to use R43S and others say to use 45S. Seems the difference is that the R43S is a colder plug than the 45S.

thoughts on all of this?

is R43S good for this engine or should it use the R45S plugs?

Interesting. I use Champion RJ9YC due to the cam and high compression, I need a 'cold' plug. The Oreilly site suggests an RJ18YC which is a much hotter plug. I suspect you might want to try an RJ12YC and run it for a bit then look at some plugs to see if you should move up or down in the heat range.

Given how few miles we tend to put on these cars I would avoid expensive plugs.

I'd give the r43 plugs a try. I have used them in marine applications which includes lots of idling and lots of high stress, full load running and they have been fine.
Pull them after a few hundred miles and look at them. If they are not fouled or excessively worn they should be ok