Just finisned off the engine on my '69 Mach1, it's a 351W that's got close to 400HP with the set up i did....just wondering what kind of spark plugs i should use and what would be the gapping on them...Thanks

 

Factory plugs are Motorcraft BF-42 and the gap is 0.034. Do some research on platinum plugs particularly NGK and Bosch. If you have an updated electronic ignition system, you can open the gap up to around 0.040.
Here is an article you might be interested in.
http://www.babcox.com/editorial/cm/cm120032.htm

 

I was thinking using Motorcraft's original spark plugs, but i'm using a pertronix ignition system, so wondering if anyone has a set up close to mine and what kind their using....Thanks

 

C'mon guys, i taught that maybe tonight would be a better time to ask my question...Thanks

 

400 HP?
Are you running aluminum heads? What kind of compression? What kind of ignition? What kind of induction? What kind of cam?...
Picking plugs w/o knowing the entire setup is like picking out the hot chick at weight watchers info night, with a blind fold on.
Not a smart idea!

 

This is my set-up: 351W block bored .030, forged flat top pistons, forged connecting rods, fully ported 3 angle job original heads( they now flow 230cfm), original intake port matched to my heads, comp cam 292H, 10:1 compression, 1.94 Ferrea intake valves, 1.60 exhaust, pertronix ignitor system, holley 650Cfm double pumper..........hope that helps

 

10:1 comp, stock heads, and pertronix, with carb. I'd go stock plugs and open them up just a bit if you've got a good coil. Then do a plug check to make sure they're working right when you get a few miles on it.
I'd be suprised if you need to change with that combination. In fact if you do need to change, I'd start looking for problems (like excessive timing). You really haven't done anything to make a plug change necessary.
Later if you add a multi-spark control box, then you might want to upgrade to a more durable plug.

Good luck,

Scott

 

Ok so if i heard you right, stick with stock Motorcraft BF-42 original spark plugs and leave the gap at around 0.034....but these are not v-groove , any gain in preformance if i were to go with let's say NGK v-groove spark plugs? Thanks

 

Nope. Nada. None. Spark plugs just start the flamefront. A single spark is all that will be produced, and it will take the easiest path to get the job done, no matter if you have grooves, 2 prongs, 4 prongs, 50 prongs.....

You'd be better off saving the extra money for an MSD 6AL ignition box. Then you can open the gap and get a little more pop.

 

Yeah, if you also have the flamethrower coil with the module, you can open the B42's a tad, but if you only have the module, I wouldn't. The platinum plugs will last longer because the platinum is a harder material, but unless you increase the heat factor on the plug, they will not burn any hotter. For instance, the B-45 is a hotter plug than the B-42. It's the last number that determines the heat factor.