Spark plug reach?

[Jeff Balazs]

Hey Guy's;

I have been looking at some options for different spark plugs to test.

But the first thing I come across is some conflicting reference data on the proper reach for our L6 engines. The plugs I have been running are 10mm reach. Is this the correct reach? or should it be a 12mm plug?

I just want to be certain before I go any further.

 

Thanks in advance.

Jeff

[Merle Coggins]

According to Autolite's online lookup they spec 306's for our trucks, and that's what I run in mine. The specs on Autolite 306 spark plugs is 3/8" reach, 14mm thread, and B10 heat range.

http://www.autolitecatalog.com/PartDetailWindow.aspx?b=A&pn=306

 

12MM reach may be correct for aluminum heads. I think they'd be too long for a stock head.

Edited August 27, 2014 by Merle Coggins

[Jeff Balazs]

Well that is what I thought......but I was looking at some cross references that were 12mm meach instead of 10mm. I wasn't sure if maybe the later flatties got a different reach or if maybe the head was revised.

 

Thanks, Jeff