RHS 12321 heads or not, need help

[68camaross]

First off, great site. I recently bought a set of 12321 pro action RHS heads from a speed shop. They looked good out of the box. I was looking for spark plugs and this is when I got concerned. The heads came in RHS boxes and the spec sheets were for RHS 220 pro action heads. On the front of the heads are stamped 223 4000 20 and RHS is stamped on top of the head in the galley between the valves and A05615 is stamped on the front of the head under the valve cover rail. In looking for plugs, I noticed on the Autolite site, they list a 14mm .708 reach plug for 12321 RHS pro action; put I also noticed under the Pro Topline it has 223 4000 20 and suggests a 14mm .460 reach. Which is the correct plug for the heads I have? Thanks.

[FASTTECH1]

The Pro Action RHS 12321 and the Pro Topline 223400020 head is bascially the same head. The only significant difference is the spark plug. If your heads actually have a RHS logo embossed in the casting it will take the 14mm .708 reach head, if it has a PRO or ProTopline logo embossed in the casting, you will need to use the 14mm .460 reach plug.

thanks

[68camaross]

Thanks for the quick reply. Tried getting through on the phone but the tech line must have been really busy. Yes, RHS is embossed in the head so I guess it is the .708 reach plugs. Hope to get the engine in the car this week and make some passes.

[FASTTECH1]

yes, should be the .708 reach plugs.

thanks