MonsterBilly

just gonna slam in some new plugs. Going with motorcrafts. Are there better plugs for these old ponys? just wondering

nba1341

According to the Hayne's Manual The Autolite (Motorcraft) BF-42 plug should be gaped at 0.034in (.086mm). That is what I set my autolite 25's too which were .045in out of the box.

1slow67

My NGKs were .035 out of the box. I opened them all up to .045 I believe.

67mustang302

Gap depends on compression, mixture quality, ignition power and so on. I have mine at about .045". The smaller gaps in the .030's were from back in the day when ignition systems sucked and couldn't generate enough voltage to jump larger gaps. They're also good on high compression or blower engines. some new factory cars run as much as .060". I use Autolite copper cores myself.

plainsman1876

I use Autolite Platnums, I believe I set them at .032 or .033

nba1341

P.S. don't slam them in too tight you'll break one!

4reboy

I'm going to put in some new plugs this week, what should I set the gap to? I have pertronix ignition/coil and MSD 8.5mm plug wires. Not sure what compression is, but it has stock heads and stock style pistons I think so compression should be stock. So with this improved ignition system, open the plugs up to what, .040?

It's also my understanding that if you have a wider gap you can use a leaner mixture. That would be great because I go through way too much gas right now, need to tune my carb and everything else.

67mustang302

A wider gap results in a larger spark, making it easier to ignite leaner mixtures...but it also erodes more quickly and is more prone to high rpm misfire. A smaller gap erodes more slowly but also retains more spark energy. The goal is to find the balance between enoguh gap to ignite reasonably lean mixtures, without going so large that you rob yourself od spark energy just from trying to jump the gap.

Crane recommends with their ignition boxes and a good coil and radio suppression wires to gap at .045" on street engines, that's a good starting point.