jeffswav

Anyone know what he difference is between the #1 and #2 ? All of the specs are the same.

Griff

I don't know the difference between the #1 and #2, but the RF #1 is a cross ref with the MR43T.
I ran them in an engine a long time ago. It was a little rich at idle and the RF's helped and did not foul out.

jeffswav

So it may be the heat range, I found a document on ACdelco's site that crossed them to the MR44. Would this be for a high compresion motor?

Griff

For AC's, the higher the number, the higher the heat range. I'm not sure if that applies to the RF's though.
You want to run the coolest plug you can without it fouling.

jeffswav

Yea, I agree. After searching many auto parts stores I found a set of new old stock #1's. ACDelco has changed the design and lowed the quality of the new product. Same part number but a completly different plug.

Flamingo 42

They used to make them in Flint Michigan then a couple years back they moved production out of the country and leveled the plant...brought a tear to my eye, can't beat the quality of the american worker

Griff

You could also try some AC R43TS plugs. Thye have a slightly extended tip.