Spark Plugs for 308 with milled 262 head

Kdancy
Kdancy Senior Contributor
in HUDSON
A few years ago there was a discussion about spark plugs (NGK B6L) 7/16" reach, touching the exhaust valves. Someone used shorter reach plugs but I can't find the discussion.
The head after milling was 1.965 thick. The block deck was just touched enough to flatten surface.
 Input appreciated!

Comments

  • Lance
    Lance Member
    Kerry,have you considered using 2 washers per plug instead of one? 
  • BillUSN1
    BillUSN1 Member

    It may be the style of plug selected.

    There are standard tips and projected/pwr tips.

    Here's a couple of the listed performance plugs for my 49.

    You can see how much difference there is at the tip.


  • Kdancy
    Kdancy Senior Contributor
    edited February 2017
    I've received a couple of reply's about the double washers. It must work as several Hudson racers have done that successfully.
    I have an NOS 308 head that I bought from Don Crane and am sending it to install on the motor. He is going to send the 262 head to me. I have a 262 to put it on.
    Thanks!
  • Ol racer
    Ol racer Senior Contributor
    edited February 2017
    FYI
    Dont despair there are solutions. Ive milled heads a little too far over the years using HiLift Cams then always rotated the motor to check clearance before starting. Ive got by simply putting in shorter 3/8 Reach Heat Range Plugs sometimes .

    However, in Aluminum Heads, I like the 7/16" Reach for extra 'holding threads'  so I side Gap the Sparkplugs with a Dremel wheel exposing the center Electrode then Gap diagonally off the side corner.Believe it or not, this actually 'enhances' the Combustion Process. Recommend practice first on an old Plug. Now days there are Video's on doing this old Side Gap Trick. Just Goggle How to Side Gap.

    Additionally, In extreme cases, I 'Index' the Sparkplug in between the Valves. You can do this simply by scribing a line with Marker Pen on each plug pointing at Tip, then install different Plugs until one plug tightens away from the Exh valve. (Might have to try  7 or 8 because each plug will snug up sligtly different rotation)

    'Indexing' is done in most racers but works for Street Mtrs too.
  • didusay39
    didusay39 Expert Adviser
    Summit sells spark plug indexing washers.
    Robert
  • Kdancy
    Kdancy Senior Contributor
    edited February 2017
    Thanks guys!  Rudy Bennett had also suggested the spark plug mod. I am going to do that on a 308 with 262 head I have on engine run stand. Will get some of the indexing washers. 
    Found a link to side gapping-
    http://performanceunlimited.com/documents/plugsidegapping.html

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