Plugs

[Guest Oldie & Goodie]

Want to change out the plugs in a 51' Roadmaster. Manual shows AC 46X.

Is this part number still valid? If not any idea what to go with in the AC line?

[Guest Bob Call]

I believe the plug number should be 46XL for extended reach, that is the 3/4 inch long threaded portion. Your can get AC if that is what you want, but, the current AC's have a different logo on them than what they had back in '51. Search for ACDelco parts on the net and go to their home page and you can search for stores near you that sell ACDelco plugs. Easy to find at places like NAPA are Autolite and NKG. The Autolite equivalent to the AC 46XL is Autolite 86. The old AC were simplily coded. The 4 = 14 MM thread, the 6 is the heat range and XL is extended length and if XLS the center electrode and insulator were also extended further than normal.

If you can't find the Autolite, NKG or Bosh at a local store, RockAuto.com has them in stock.

[Dave@Moon]

From Spark Plug Cross Reference:

Convert from AC_DELCO 46xl.

<table padding="0" spacing="0" border="0" width="100%"><tbody><tr><td width="110">NGK P/N: </td><td width="110">B5ES</td></tr><tr><td width="110">NGK STK: </td><td width="110">6410</td></tr><tr><td width="110">Autolite: </td><td width="110">397</td></tr><tr><td width="110">Beck Arnley: </td><td width="110">176-5058</td></tr><tr><td width="110">Bosch P/N: </td><td width="110">W10CC</td></tr><tr><td width="110">Bosch STK: </td><td width="110">7510</td></tr><tr><td width="110">Champion P/N: </td><td width="110">N5C</td></tr><tr><td width="110">Champion STK: </td><td width="110">120</td></tr><tr><td width="110">Denso P/N: </td><td width="110">W16ES-U</td></tr><tr><td width="110">Denso STK: </td><td width="110">3025</td></tr><tr><td width="110">GM OEM NR: </td><td width="110">5612022</td></tr><tr><td width="110">Mighty: </td><td width="110">M4G3</td></tr><tr><td width="110">Motorcraft P/N: </td><td width="110">AG4</td></tr><tr><td width="110">Prestolite: </td><td width="110">14G5</td></tr><tr><td width="110">Valley Forge: </td><td width="110">205</td></tr><tr><td width="110">NGK TYPE: </td><td width="110">AUTOM.</td></tr><tr><td width="110">Thread size: </td><td width="110">14MM</td></tr><tr><td width="110">Hex size: </td><td width="110">0,81</td></tr><tr><td width="110">Reach: </td><td width="110">0,75</td></tr><tr><td width="110">Seat type: </td><td width="110">GASKET</td></tr><tr><td width="110">Projected tip: </td><td width="110">NO</td></tr></tbody></table>

The same web site lists no conversions at all for an AC 46X, which may not exist.

[Larry Schramm]

The "S" on an AC plug identified it as a skirted plug. What you had was a little bit of non threaded area below the threaded area. That was the S/skirt that gave you a little more reach.

[Guest Oldie & Goodie]

Thanks for the info.

I'm sure I can track something down now even if I don't stay with AC.

Edited September 7, 2010 by Oldie & Goodie
spelling (see edit history)

[Joseph P. Indusi]

Buick Shop Manuals and Motor's specifies AC 46X for all straight eights 1950-53. I have 8 new ones.

Joe, BCA 33493

[Guest Oldie & Goodie]

Buick Shop Manuals and Motor's specifies AC 46X for all straight eights 1950-53. I have 8 new ones.

Joe, BCA 33493

PM sent.