Re: V8 spark plug fitment?

Posted by Dave Brownell On 2016/8/14 10:27:29

The Executive hardtop, with a build date of March 22 shows a casting number of what I believe to be 6480408. That's close enough to your 6480407 for me to try the longer thread Autolite 66s. Just for grins I also checked the June 14th built Esquire and it also has the 6480408 heads on it. It's running fine but I may pull the easiest to get to plug to see if it has the longer thread in it. I'll do a depth measurement on the Executive before committing to change anything more, unless I am certain.

On a related note, should we give consideration to amending the forum's Parts X-Ref to showing specific 1955 and 1956 differences in applications? All V8s might not be accurate. I'll leave that up to the experts on these engines.