Plugs for 1983 Aluminum Bowtie Heads?

[G B.]

I have a set of aluminum small block heads with casting number 14011049. These were sold over-the-counter by GM in 1983 as angle-plug racing heads. I think their target use was on NASCAR type engines.

I'd like to use these heads, but I can't find any reference material on what plug design to use. They are machined for gasketed regular (not peanut) head plugs. However, the thread depth is much deeper than for a standard sixties-type small block plug.

Can anyone recommend a specific 13/16" hex-head plug with about 3/4" of threads that is equivalent to an AC 45 heat range? It might be risky to install a projected tip with 1/8" domed pistons, so I'd prefer a recessed electrode tip.

I recall that sixties big block plugs had a long threaded portion. Is that design what I need?

[Joe L.]

Re: Plugs for 1983 Aluminum Bowtie Heads?

Jerry-----

The GM #14011049 CASTING was available until January, 1999, although most of the finished cylinder heads manufactured from this casting were discontinued well before that time.

Most, if not all, of the finished cylinder heads manufactured from the GM #14011049 casting were machined for the use of BOTH gasketed-type spark plugs as well as tapered seat spark plugs.

The gasketed type plugs which are recommended for use with this cylinder head would be the "XL" suffix series plugs as used for big blocks. For example, the AC R45XL would be about what you're after, but these do have extended tip. For Champion Plugs (which are always my favorite for Chevrolet engines), you would use the N-series plugs (as also used in older big block engines). An N5C might be about right. This plug has a non-projected tip.

[Mark #28455]

would indexing the plugs help?

Draw a line on the porcelain on the side with the grounding electrode, use variable thickness washers like sold by Moroso to get the electrodes to the top side (away from the pistons).

Mark

[Clem Z.]

just remember every .020 you move the plug

you change the timing about 1 degree,in advances,out retards the timing. you are better off just moving the plugs around from hole to hole

[G B.]

Thanks for the help.

I bought a set of Champion N5C plugs today. They fit these heads just fine.

The box said this plug design is also known as a #120. It crosses over to an AC 44 / 45 heat range. It was originally made for some motorsickle according to the CarQuest counterman.