Ron, All second gen Olds V8 engines from 1964 to 1972 will use a 45S or 44S or 43S AC spark plug. I'll bet anyone $1 million on it. A "S" series AC plug is an extended tip is get the flame front into the center of the combustion chamber at TDC-firing. A standard AC 45 or 44 or 43 plug does not have an extended tip and is not as efficient as the extended tip plugs in an Olds. Actually, an AC 45 or 44 or 43 plug is a small block Chevy plug, particularly in a small block Chevy with high compression, for an extended tip plug will hit the dome on top of the small block Chevy high compression piston. That's the advantage of an Olds with high compression flat top pistons...no spark plug interference.
The difference is in the spark plug tip, not in the number of threads. An extended tip AC plug and a standard tip AC plug have the same number of threads. The electrode tip is 3 times as long on an extended tip plug than on a standard tip plug. If someone gave you spark plugs that actually have twice as many thread rings than the plug in your 400 Olds, then someone gave you plugs for a *****427 Chevy*****, not a 425 Olds. What spark plug brand uses an E3.46 number. I don't recognize it? Use an AC 44S plug or equivalent. Nothing else, and you should stay out of trouble. Milton Schick 1964 442 Cutlass [EMAIL PROTECTED] ----- Original Message ----- From: "Ronald Forsee" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Monday, November 20, 2006 1:11 PM Subject: Re: 425 ci > > > Hey Gurus! > Remember that little blurb I sent asking about your thoughts on > whether or not a 425 plug would fit my 400? Well I bought them (E3.46 > supposedly for the 65 Starfire 425) and they aren't even close. They > extend into the chamber a full 1 inch where my current plugs are > considerably shorter (about half the number of threads). Can anybody check > their 425 plugs for me? > > > Ron Forsee > > 65-442 Orig-Owner > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.430 / Virus Database: 268.14.14/548 - Release Date: 11/23/2006 3:22 PM
