<VV> Re:Delco Rapidfire Spark Plugs

[Frank DuVal]

>Looking on the Delco web page, they show the RapidFire #4 as a substitute 
>for the W8AC & R43F. SInce Rapidfires generally replace 42-43-44-45 ranges 
>I wonder if anyone has ever tried them in a Corvair.
>
>Did find that threads are measured in "reach", the distance from the gasket 
>seat to the end of the threads with a 44 having a 3/8" reach, 44L 7/16", 
>44F 1/2", and it looks like the original 44FF was 9/16".
>
>The interesting thing is that a #7 RapidFire (Pontiac 400) despite only a 
>3/8" reach has an extended tip which makes the distance from the gasket 
>seat to the top of the electrode almost exactly the same as a W8AC.
>
>And just for fun, the gasket measures 1/16"
>
>Am curious, has anyone ever run a 44S or 44L  or RapidFire #7 in a Corvair 
>? What happened ?
>
>Padgett
>  
>
>  
>
There was some discussion years ago when the FF series was discontinued 
and the F series was the recomended replacement. The FF series had 
threads all the way  to the end of the plug, and the F series has like a 
starter area with no threads. Common thought at the time was the lack of 
a thread would allow carbon to build up in the thread void between plug 
and head. This carbon may break off during plug changes and fall into 
the head. In the years since I have not had a problem with this. But 
going to a 1/8" area to build up carbon may present a problem. Anyone 
have real world experience?  I do know the 3/4" reach plugs used in the 
Chevy sixes (194, 230, 250) look real funny stuck in a Corvair head. I 
have pulled several of them out over the years. Most have not been 
installed far enough in to seat the gasket.

Frank DuVal