Re: tuning questiion
 

Read this article on selecting the right heat range.

http://www.moparmusclemagazine.com/t...s/viewall.html

You start from there then move on to gap and timing.

Re: tuning questiion
 

That story doesn't say much at all about how to select a heat range but what's there, if anything, confirms what I said earlier about plugs.

But...if the plug originally developed for the engine was an AC 1 heat range, unless the engine is in a trailer queen...why is everyone running such hot plugs?

Do they know more than the engineers who spent years testing plugs?

I'll stick with my Denso 22 heat range.

But I will grant you, for engines which see a lot of starts without warm-ups, are running too rich at idle and part throttle or are using oil, the cold plug is a mistake.

Re: tuning questiion
 

Great post. Thanks !

Re: tuning questiion
 

Click in the pics of the various plugs. The one w high miles
but in good condition. Read the material there. It describes how to choose plug heat range using the coloring of the ground strap. This is really well known in performance circles. Nothing new actually. You don't pick heat range based on the color of the ceramic.

Re: tuning questiion
 

Well I haven't heard that much about using the color of the ground strap to select heat range.

But, heck, maybe I've not been in "performance circles".

Re: tuning questiion
 

I have never deviated more than one heat range from 'stock' (if known) for any particular engine incl mild street supercharged applications.

The one time I got some free plugs that were 3 or 4 heat ranges colder that I threw into a tpi 305 camaro, it immediately failed to meet the max allowed hydrocarbons on the two speed idle emissions test that we used to use here. (I worked at a shop and we had the 4-gas bar-90 machine). It idled fine, ran fine, ...just ran dirty at idle loads.

if you don't run catalysts, I suppose it doesn't much matter.