spark plug questions

[hamondale]

Searched the archive and found some info on plugs, but not everything I need -
I'm switching back to AC Delco spark plugs in my 3.4 crate motor. I can't find any specific reference on Goodwrench or AC Delco as to what plug should be run in this motor - the ACD web site only allows specs by vehicle - model - year.
Would say, a 93 Camaro 3.4L be a reasonable surrogate ? - The ACD site comes up with R43TSK as a standard plug.
I have an MSD 6AI ignition, so should I gap higher than the 0.045 listed on the ACD site? Maybe 0.060?
Finally, are the platinum or Rapidfire plugs any better for performance? This is not a daily driver, it's a hot rod that only seeks a couple thousand miles a year. I'm not all that worried about life. Oh one other thing - this is a carbed engine - Offy intake and Holley 390 4bbl.
Thanks for any insight.

[geoffinbc]

Yes the Camaro engine is the correct engine to pick on. If you have a hot ignition I suggest opening the gap. On regular Delcos I was running a .070 gap (no im not lying) I never got a misfire even up to 6000 RPM rev limit. Idle was super smooth. If you wana spend the bucks go with the platnium's they do give off a hotter spark and last so much longer. You will notice a slightly better idle too. You can gap these as well but be very very careful.

[hamondale]

Thanks BTY. I think I will try the platinums, I stopped in to the local chains today to get some, but they have to order them. This is a small town area, I guess inventories are not all that good. I will have them in by Tuesday. Appreciate the advice.

[geoffinbc]

Whe I gapped my iridiums I used a flat blade screwdriver to open the gap up and used a set of calipers to measure it as I opened it up. I tried a conventional gapper on one but broke the tip. Luckily my parts guy gave me an new one at no charge.

[hamondale]

Thanks, I was wondering what the trick was to gapping, but haven't seen the plugs yet.

[geoffinbc]

They look the same except the electrode is very tiny at the end. About 1/4 the diameter of a standard electrode so it is easy to break.

[hamondale]

Well I got those plugs in over the weekend. For gapping, I slid a small hard plastic tube fitting over the grounded part, put the shaft of a small screwdriver between that and the threaded boss for a fulcrum and just pried the gap open farther using the fitting as a lever.
Boy, 0.060 gap sure looks larger than what I'm used to, but it seems to run fine. What's better about a larger gap? Is it just more spark volume so it lights the fuel better?
BTY, thanks for the advice on these.

[geoffinbc]

Bigger gap means a larger arc. More exposure area to fuel vapor so it will light easier and it will burm more completly.

[Juglenaut]

Be careful gapping iridium, or platinum plugs. You may not want to pry on the electrode to much as it may break up inside or on the surface or close to the body formation especially with iridium plugs they tend to break up inside the body and still work but will fail sooner as the spark will erode the faces between the crack.

Instead put the plug in a table-top vise tighten, and clamp snug with a vise grip pliers (not squeeze the crap out of the prong) then gently pull up and as close the the same direction as the bend in the prong, the trick is here is not to mutalate the electrode face and keep the prong as close to parallel as possible. This process can be used to lessen the gap as well, also allows for better gauge of adjustment.

I am interested in the hard plastic fitting you used though, can you explain in detail.