emsrescu

I have the edelbrock performer rpm heads and was useing normal plugs for a 77 350 chevy. Well the plugs were 1/2 inch too short. Check to make sure if you change your heads that they don't need a longer plug now. Mine runs alot better now. :crazy: :smash: :cheers:

Desertdawg

This is some good advice. I friend changed heads and didn't realize that he needed to also switch to the short plugs....I guess you know what happened first time he revved it....

Marc80

I also have the same heads and you make me wonder. When you get a chance...what is the length of your plugs.

Thanks in advance,

Marc

Nomad78SA

You are so right....
I had TFS 23 degree heads on mine for a while and had the wrong plugs in. Way to short. Motor reved great and I had no idea. A friend of mine noticed the problem one day while we were working on the vette. Car had never been on the road yet though for it is in a frame off.
Man was I humbled that day
Neil in Tenn

Vetterodder

The manual that came with my RPM heads recommended the longer plugs so I used them from the start. I still had a problem though due to my domed pistons and, until I indexed the plugs, they contacted the domes just enough to close the gaps on those that weren't positioned right.

no_radio

AFR had a recommended plug on their web site, so I bought a set as a starting point. From there, only hotter or colder depending on the performance.

So far, so good.
Jeff

redwingvette

Not only the length can be different but the seat can be too. The RPM heads state in the paperwork to change to a plug with the gasket seal. The stock plugs were a tappered seal. Edelbrock also recommends a plug number to start with. Sorry, I can't remember what number. If anyone needs it I can look it up and post it.

Vetterodder

My manual called for Champion RC12YC4's (aka 71's) and I've had good results with them. I've also used other brand's equivelents with good results also. While they were all the same length inside the cylinder, some were longer or shorter overall, resulting in different clearances with my headers. Autolights were longer than the Champions, AC's were shorter. While the heat range of the recommended Champions is just fine for me, different combinations of parts and usage might make another heat range, higher or lower, better. Another issue is availability. One dealer may stock the plug you need in one brand but not another so convenience may also be a consideration.

emsrescu

they are .750 i am useing autolite 3924