I have a '71 350 that I rebuilt with 9.8:1 compression and a lunati cam. I found a good deal on a accel coil(point type). Should I make the plug gap wider? Accel says no, but I have heard the opposite. Thanks a lot.

 

Gap them at 0.035 and you'll be fine.

 

Thanks a lot.

 

Unless you actually have some technical specs to compare the two coils, you might as well flip a coin if you're set on changing the plug gap one way or another.
My opinion on the whole aftermarket ignition "upgrade" thing is to compare it to a cam swap. If someone handed you a new aftermarket cam in a plain brown wrapper, would you use it? I'm guessing not. Without specs to compare the new cam with the cam you already have in the engine, you might as well flip a coin to make your decision. Or, just stick with what you have that you know works.

ps: I used to live in Kokomo. Where the heck is Huntingburg?

 

The accel coil is advertised as 42,000 volts. I would guess that's more than stock. Huntingburg is in dubois county in the southwestern part of the state. It's about 5 miles from Jasper.

 

The voltage rating of a coil is not a very useful (on a day to day basis) bit of information. (Energy, not voltage, is the important item.)The voltage seen in the system secondary side is controlled by the plug gap and condition, along with the cylinder pressure. Most of the time the plug voltage will be in the 15-20,000 volt range, with crappy plugs perhaps needing 30,000 volts. The 42,000 volt rating is primarily for marketing use.
A simple analogy might be someone advertising that their air compressor tank is rated at 1000psi burst pressure, while someone else's is rated at 500 psi. The 1000 psi tank, while sounding good, does you no good relative to the 500 psi rated tank when the pump shutoff regulator is set to 125 psi. I would rather have a large tank rated at 500 psi burst pressure, than a small tank rated at 1000 burst pressure, as each has identical pressure (125 psi). There's more air (energy) in the lower burst rated tank than the higher rated tank. And remember, you want energy. We have no clue if this Accel coil will provide more, or less energy. We need electrical specs to find out if you are gaining or losing.
Sorry, don't know how to explain it any more without a bunch of formulas. (Hope you managed to stay awake through the description. )

 

I think 69427 is trying to say is you don't really know what kind of coil you have. A 0.040 plug gap requires more volts to jump the gap than a 0.035 gap. A coil won't be efficient at jumping a gap larger than it was designed for and could shorten the life of the coil. A proven high performance coil such as MSD or DUI would allow you to run a larger gap but you should also install a matching module.

Being able to run a larger gap will improve combustion.

 

Thanks for the help. I guess I will leave the gap at .035. I mainly bought this coil to replace the original 35 year old piece when I rebuilt the engine. It was on the clearance rack at auto zone for $15. I saved the original.

 

I'm not trying to be difficult here, as I do agree with the basics of your post here, but I do have to disagree with the "proven high performance coil" statement. I go back to my earlier "cam in a plain brown wrapper" comment. Unless these aftermarket ignition suppliers give some actual electrical or engineering specifications, you've got nothing to compare against. I just don't see the wisdom of buying any aftermarket part if you can't determine (before you pay your money) if it is a step up, or a step down.