nba1341

Hello I am replacing my old spark plugs

I pulled them all out and they look great now that I finally got my car to not run so rich


Anyways the old ones had a heat range of 4 and the new ones are just autlite 25s with a heat range of 5. Should I have been running a heat range of 5 in the first place I have no power adders or anything and stock heats.

And what is the gap suppose to be? The old ones were at .35 the 25's out of the box are at .46.

350kmileFord

Don't ever trust the gap right out of the box. Always double check. What ignition are you running? It should have a recommended maximum allowable gap. And, I've never used one, but there's spark plug 'testers' that allow you to hook up a wire and adjust the gap (it acts as a mock spark plug) that may give you an idea.

stephen.osborne1

anyone know about what gap you can run with the pertronix (original pertronix) and a 40,000 volt coil? All the adds say you can run a wider gap, but fail to specify what the gap is.

kalli

if you increase you will be able to burn a leaner mixture (since there is better chance of having more fuel molecules where the spark happens). However if the gap ius too wide at hiogh rpm you'll blow it out lie a candle. noone could give you a recommendation on what will be best. trial and error. however 1mm should be safe to start trying from (0.04") assuming it's a standard spark with one ground strap, no grooves, and not a pointy tip plug ..

stephen.osborne1

I use motorcraft platinums, nothing fancy but was looking at maybe NGKs in the future as I need to upgrade wires when I get home anyway... Now that I think of it, I need to get the wide dizzy cap too... Oh so many things I can't wait to play with when I get home...

71Mach14spd

My 351c thats pushing 500 hp with roller cam, bored over MSD coil/dizzy/and 8.5mm wires etc is gaped at .35, while my trucks 460 that is closer to stock are gaped at .46 so i think that no more than .35 would be fine for you.

urban_cowboy

You mean .035-.040 right? And yes, I would say .035 to .040 with a stock type ignition. You can run more (.050 or so) with something like an MSD, but all of that depends on the compression ratio, chamber shape, etc.