<VV> Tune up questions

[Jim Davis]

The extended tip spark plugs were an attempt to prevent "glazing".   
This is where the engine is cold soaked at temperatures below zero.  
When the engine fires for the first few times, the water from the 
combustion event tends to freeze on the porcelain tip, shorting out the 
plug; thus, the engine dies and won't restart.  Extending the tip warms 
up the plug faster and can help prevent the problem.  AC 44FFS were 
available for this problem.

I find the NGK has a better selection of heat ranges for Corvairs.  All 
my Corvairs have CR of 9.6 or higher thus need colder plugs than the 
standard 44FF.   NGK have BR5HS (same heat range as 44FF) as well as the 
BR6HS which is equivalent to the 42FF.   There is also a BR6HIX if you 
prefer a cold plug with an iridium tip.
Jim Davis


  On 1/17/2013 10:54 AM, Frank DuVal wrote:
> That's what I was wondering about the two Autolite plugs listed.
>
> The 425 is a "normal" tip in description and picture on their website.
> Looks like an AC 44F (first thread missing).
>
> The 275 is a "power" tip in description and picture. Just like the
> extended Champions people didn't like back in the 70s. They thought
> engines suffering holed pistons were more likely to have been running
> the extended tip Champions than normal tip plugs.
>
> Spark plugs should be changed when the electrodes form sharp points. OK,
> before then! ggg   With high energy systems, gaps can double in size and
> the engine still runs.
>
> Frank DuVal