The car currently has Bosch +4 in it. They have 16,000 miles on them.

Would AC Delco Rapid Fires help?
What heat range?
What Gap?

They Dyno guy said usually Autolites do a few horsepower more in any engine than an AC Delco plug based on his experience.

Which Autolite plug should I try?
What Gap?

I don't care if it's a Ford part if I pick up ONE horsepower from it.

He said that indexing the plugs was absolutely worthless on a car with electronic ignition and a strong coil. Any thoughs on this?

 

hmmm, that is an interesting comment, i think you would have to have a really strong/aftermarket coil. If you think about it, one of those should be able to throw a spark across a plug with a one inch gap .

However, cant you run to hot if you have too much spark. Isnt that why you gap em in the first place?

Ask pablo for his weblink to the unending world of sparkplug knowledge.

 

While some strong coils might be able to throw a spark across an inch gap out in the open, it's a much different story inside the cylinder. The high pressure in the cylinder when the spark plug fires makes it a whole lot more difficult to bridge the gap.

 

it was a nonliteral statement, meaning, "damn those coils are hi voltage, wow"

And if you had one you probably wouldnt have a big problem if your suggested gap was a little to much. You would just want all of your plugs the same right, so you didnt have better spark in one cylinder than the other. But a good coil is going to allow you to have a larger gap than stock specs.

Am I right, I mean Im not claiming to be a master of plugs here. Just throwing out ideas.

 

Just run regular AC delcos if you plan on changing. If i were you id just leave the bosch +4 in there, i would hope they would last atleast 30k miles.

Dont buy into all the sparkplug gimmickery (if thats a word) and if you have a stock motor, stay with the stock heat range. As for gap, generally they say you can open up the gap a tiny bit with a hotter ignition setup. BUT as you increase horsepower (cyl pressure) the more energy is required to jump that gap so you might have to bring the gap back down.
Spark plugs arent magical horspower adders you just need to find the right one for your motor and i dont really mean brand wise as they all do a fine job. If you really want to squeeze some horsepower out of some standard plugs, index them. The goal of indexing is aiming the most open end of the spark plug to the intake valve where most of the fuel and air is on the combustion stroke. This is accomplished by special washers of varying thicknesses since when you tighten down the plug it can be 180 degrees off with the stock threading in the head.
Since you have the +4 plugs, indexing isnt really possible or neccessary since the gaps are to the sides

[This message has been edited by Pablo (edited November 05, 2000).]

 

Pablo,

Thanks for the info. I'll check the plugs to see how they look and do wires and coil.