Spark Plugs for Slant Six?

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1966DartConvertible

1966DartConvertible

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Hi, i cant find any thread on spark plugs...

So here goes...Whats the best spark plug to use on the Slant Six? I would prefer if you could tell me in terms of "NGK equivalent" as it is almost impossible to find Champions or the likes this side of the Atlantic.

Im thinking either BP5ES or BP6ES? Are they any good? Oh more importantly, will they FIT?

Thanks.

Syed
Malaysia
 
Yup. Dan is the man. He know which plugs work well. Follow his advice and you won't go wrong.
 
Looks like ZFR5N3459 and I gaped at .35 to .38 for my build .
 
NGK plug number ZFR5N is a very good choice. 3459 is the US stock number for that plug, but stock numbers may differ in other countries; the actual plug number is ZFR5N. Remember to remove the metal ring washers from the plugs before you install them.
 
Dan, are those the right plugs for my engine as well? It is a 1975 225 with the small plug head. Thanks.
 
No, the NGK ZFR5N fits only cylinder heads made through '74. For the '75-up heads you need a taper-seat plug such as an NGK UR5.
 
slantsixdan said:
NGK plug number ZFR5N is a very good choice. 3459 is the US stock number for that plug, but stock numbers may differ in other countries; the actual plug number is ZFR5N. Remember to remove the metal ring washers from the plugs before you install them.
Click to expand...
How do you remove the metal ring?
 
What's the point of removing the washer? Why is this necessary? Everyone says to take them off, but no one says why, and what would happen if you left them on.
 
Drool tube is the only gasket needed in the 63 and later tube heads. The very early ones 60-62 had a flat spark plug seat in the head and needed both drool tube and spark plug gasket. Peanut heads had the tapered seat peanut spark plug and no tubes.
 
slantsixdan said:
No, the NGK ZFR5N fits only cylinder heads made through '74. For the '75-up heads you need a taper-seat plug such as an NGK UR5.
Click to expand...
I know this an older post, but I go through and do some reading.

I have a '65 slantsix head, and the plugs it came with last year, when I bought the car, were NGK R, GR4 V-Power plugs. Should I replace?
Thanx
 
An NGK 4 is a hotter plug than optimal. Put in the NGK № ZFR5N plugs (that's one heat range cooler, and with the extended electrodes). NGK stock № 3459. Remove the ring gaskets before installing the plugs.
 
slantsixdan said:
An NGK 4 is a hotter plug than optimal. Put in the NGK № ZFR5N plugs (that's one heat range cooler, and with the extended electrodes). NGK stock № 3459. Remove the ring gaskets before installing the plugs.
Click to expand...

NGK № ZFR5N plugs. Will do.

I enjoy and learn from your old posts.
Thanx
 
slantsixdan said:
An NGK 4 is a hotter plug than optimal. Put in the NGK № ZFR5N plugs (that's one heat range cooler, and with the extended electrodes). NGK stock № 3459. Remove the ring gaskets before installing the plugs.
Click to expand...

Dan, I have a 225 slant with a larger than stock cam in it (specs unknown unfortunately) would you still recommend the NGK 5 or should I go one hotter? I always put minimum 93 octane in it as a matter of course. Also, any thoughts as to the gap for said motor?

A video if it running FWIW



Thank you so much
Mario
 
Sounds like a rumpity cam in that car. What do the current plugs look like when you pull them after going for whatever kind of drive you usually do with this car?

Plug gap: What kind of ignition system are you running?

93 octane: Why? Does it ping on mid-test or regular? Because if it doesn't, all you're doing is pouring money out the tailpipe.
 
slantsixdan said:
Sounds like a rumpity cam in that car. What do the current plugs look like when you pull them after going for whatever kind of drive you usually do with this car?

Plug gap: What kind of ignition system are you running?

93 octane: Why? Does it ping on mid-test or regular? Because if it doesn't, all you're doing is pouring money out the tailpipe.
Click to expand...



Plugs:
DSC09358.JPG
DSC09365.JPG


From 1-->6 .30 .28 .28 .30 .28 .28 gaps. Autolite 165's. And now that I notice it, (#3 that I just pulled) has the ring on the plug. (74 Dart Swinger)

This was after a drive towards the end 2018 (she's been in dry dock the past year and change)

Ignition is Mopar 3874020. Brand new (to me) That I purchased from Halifax Hops and installed it a month ago

DSC04662.JPG


The dizzy appears to be a run-of-the-mill stock Mopar unit with vac advance.

I have always used 93 in all of my old cars cuz the gas is crap around here (Chicago) and figured just go with the best rating I could find.
 
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Plugs don't look bad. You'd probably have better driveability with the NGK ZFR5Ns (remember, no ring gaskets).

Mopar electronic ignition is better than breaker points, but you can do a whole lot better and an upgrade would pay benefits in how the car runs. Whether or not you upgrade, read and follow the suggestions in this long (but worthwhile) thread.

Your plug gaps are too small even for the relatively weak Mopar electronic ignition. If you stay with that ignition, run 0.035".

93-octane gasoline is not "the best rating". It is not better than lower octane grades, just different in exactly one way: it's more resistant to ping (preignition). If the engine doesn't ping on mid-test or regular, there is no advantage to high-test. The only exception is if you live one of the few places where you can still buy one grade of gasoline without ethanol in it, and that grade is the highest octane offered.
 
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