Packard Forum Index » Post-War (1946-54)

So my '51 327 has a '48 head on it that takes 10mm plugs.

When I got the car it had Champion UY6 installed.
I cross-referenced this over to an AC M8 (Which is a marine plug) and the car ran terrible. Tons of carbon on the plugs.

I'm looking at the manual for a '48 and they specify Champion Y4A. Is that what I should be using?

The AutoLite website recommends AutoLite 3136 for all postwar Packards with 10mm plugs.

Hi Dave:

Champion UY6 means Auxillary Gap (u), 10mm (y), heat range 6

Champion Y4A means 10mm (y), heat range 4, Conventional a

Under the Champion system the lower the number the hotter the plug so a 4 is a hotter plug than a 6.

Under AC the higher the number the hotter the plug.

The AC M8 is more resistant to fouling than Champions.

I would look for another reason for poor performance than spark plugs.

Good Luck.



PS I have no idea what Auxillary Gap means

Auxiliary gap or resistance gap means there is a gap in the electrode between the tip and the plug wire. This acts as a spark intensifier like the ones they used to sell at the county fair. Helps prevent fouling and gives a hotter spark especially if the gap is a little wide or the ignition not too hot.

I agree with Tim about looking beyond the plugs. I've installed the M8s for years in customer's cars with no complaints.

Thanks Rusty:

Here is a patent application for Auxillary Gap:

Patent Application #4,549,114

Spark plug for externally ignited internal combustion engine


Abstract

"To increase the spark intensity delivered from a spark plug, an auxiliary spark gap (33) is serially connected with an auxiliary capacitor (37) and the main spark gap (42), the auxiliary capacitor being charged through a charging circuit including a resistor (45) connected in shunt to the auxiliary spark gap (33) and the auxiliary capacitor, and a further or second resistor (46) connected in shunt across the auxiliary capacitor and the ground or chassis electrode (15), and a shunt capacitor (51) is connected between the main spark plug terminal (27) and the ground or chassis or counter electrode (11, 15) so that, upon breakdown of the auxiliary spark gap, the main spark gap will have a voltage thereacross formed by the charge voltage of the main or shunt capacitor (51) and the additional voltage on the auxiliary capacitor (37) which had been charged through the resistors connected across the auxiliary capacitor and to the main spark plug terminal (27) and the ground terminal or electrode (15) respectively."

I don't know if AC plugs have this gadget, but if they don't then maybe that is why they seem to be more durable because this stuff looks like a gimmick that develops opens and shorts.

Sounds a little like the "spark enhancer" advertised in the back of almost every car and mechanic magazine of the 50's. Some kind of gadget that plugged inline between the center terminal of dist and coil. Was guaranteed to intensify the spark for reliable starting, increased power and mileage and make your car run like new. A side benefit was to almost eliminate having to change or clean plugs. Just think, if everyone had bought one of those and some of the other gadgets available, we'd be self sufficient in oil, with like new 50 year old cars everywhere.