Best Spark Plug for my 250?

[michael_cini]

I know this subject has been covered, but the more I read the more questions I have. The Ford I6 handbook suggests an extended tip plug. What would you suggest for a '75 250 motor modified with an OZ head (milled, oversized valves), Holley 350cfm carb, 264/274-110 cam driven in Southern California?

I found this post by CZLN6 (below), but could not find these Champion plug numbers locally. I could find the Champion RF18YC. What is the difference? Heat range I assume?

On spark plugs, I run Champion RF14YC winters and RF11YC summers. They are cheap, they set the industry standard for "Extended tip" design. They offer a wide choice of heat ranges and are availabe everywhere. Did I mention that they are cheap?

Advice would be appreciated. Thanks.
Michael

 

[rbohm]

8) i quit using champions years ago because they would never live in my old chevy pick up. i use autolites pretty much in everything these days.

 

[jb1rd]

The only info I can offer is that US type plugs run lower number such as RN11YC is colder than RN14YC is hotter, and so on it goes with US plug mfgrs.

 

[wallaka]

NGK IRIDIUM IX WR51X stock #7510.

The NGK plug is the latest in technology, it has a pin center electrode which requires less voltage to fire & the center electrode is iridium which will last 100,000 miles in a engine in good shape. Yeah, they're pricey, like $7 a piece. You get what you pay for sometimes, though.

Best plug out there. IMO.

 

[350kmileford]

Couldn't one increase the gap in their NGK IRIDIUM IX WR51X stock #751s past the distributor's recommended range? (since they require less voltage?) I'm using the DSII kit that Mike sells and they only recommend a .055" max.

 

[powerband]

The Ford '6' engine can use Champion 'RF' series plug :
1. 18MM Thread
2. .460" Reach
3. 13/16" hex
4. Tapered Seat
The Heat Ranges run as follows:
Hot #RF18YC (#11)
RF14YC (#21)
RF11YC (#22)
Cold RF9YC (#409)

"Champion Racing" - Small six application still available : Champion' "Racing Plugs" Part # 2021's. Hope this is what your looking for, don't know how it translates to "Modern" plugs.

"Indexing" the plug's gap on the radical built 250 to face the charge is attempt at really splitting the curly hairs of performance.

(...indexed)

Have Fun

Powerband