What spark plugs should I use

rpengr · **Posted:** Tue Jul 30, 2013 12:35 pm

Here are pictures of my current spark plugs. Age is unknown, but probably 3 years. Champion RS12YC.
I am replacing. Should I stick with the same type? What does that black band on #8 mean? Does anything look abnormal?

Plug numbers
1 2
3 4
5 6
7 8

ric · **Posted:** Tue Jul 30, 2013 2:40 pm

It means the crappy factory intake manifold isn't equally distributing air/fuel. Common. That's why you can get 20hp with an aftermarket one.

Personally I'd go with the updated VP/MC part # for iridium plugs.

Graham R · **Posted:** Tue Jul 30, 2013 4:21 pm

The black band on one plug means it's an original one ! : from when VP used to paint their engines black, it was the bit that wasn't covered by the ignition lead boot when they sprayed it. Why you had 7 replacement ones and one original, who knows, maybe they dropped one of the 8 new ones and broke it. To be honest, it looks no different on the working end to the rest.

These new long life plugs Ric refers to are incredible; I just checked the (platinum) ones on my 3.0 V6 Ford Duratec; 65,000 miles ( should have been changed at 60,000 miles), the gap was still spot on and they looked more like plugs that had done 5,000 miles, not 65,000.

Everyone has different tales about spark plugs, how some makes are superior to others. I had always sworn by NGK. However, my petrol hedge trimmer recently refused to idle once it was picked up . Turned out to be the NGK spark plug, the insulator around the electrode had fractured and was sliding forward as soon as the tool was picked up, eliminating a spark.

deafwish · **Posted:** Tue Jul 30, 2013 4:36 pm

Whichever you decide to use, remember that corrosion will still occur in the same timeframe.
Don't forget to use copper grease on the threads this time! :wink:

Graham R · **Posted:** Tue Jul 30, 2013 4:52 pm

deafwish wrote:

Whichever you decide to use, remember that corrosion will still occur in the same timeframe.
Don't forget to use copper grease on the threads this time! :wink:

A very good point; I use a colloidal nickel product that I was given many years ago as a free 500 ml sample when I worked in the plastics industry (an anti seize product for injection moulding machine screws), never an issue with corrosion of the plug threads (or any thread for that matter).

After 25 years, I still have 90 % of it left !

LouC · **Posted:** Tue Jul 30, 2013 4:54 pm

Actually the color on the insulators on those plugs looks fine to me. I know some don't like Champions but they have been fine in my Mopars (Jeeps). With the boat I have good luck with the Delco Marine plugs. Look for the source of the corrosion on #2, manifold drain or hose drip?

rpengr · **Posted:** Wed Jul 31, 2013 7:42 am

The color looked fine to me, but I wanted some other opinions. I just purchased a set of the exact same plugs and will install tonight. I will coat with T-9 rust preventative, and maybe Tef-Gel on the threads.

Thanks for all the replies.

Ray

Winter Sux · **Posted:** Wed Jul 31, 2013 11:07 am

Your plugs are fine and +1 on the Teflon.

rpengr · **Posted:** Wed Jul 31, 2013 11:55 am

Does anyone happen to know what is the proper gap?

Toddely · **Posted:** Wed Jul 31, 2013 12:02 pm

What engine is yours. I just put new plugs in mine and its a 5.7 Gl and the gap was .043 Per the dealer.

rpengr · **Posted:** Wed Jul 31, 2013 12:24 pm

Toddely wrote:

What engine is yours. I just put new plugs in mine and its a 5.7 Gl and the gap was .043 Per the dealer.

Thanks. Mine is 5.7 GS. Vortec Head. I noticed your plugs are the short style, mine are long.

Toddely · **Posted:** Wed Jul 31, 2013 1:05 pm

Just checked and yours is .045 I have the dealers number here in my truck (Handy)

rpengr · **Posted:** Wed Jul 31, 2013 2:13 pm

Toddely wrote:

Just checked and yours is .045 I have the dealers number here in my truck (Handy)

Thanks Todd.
It just occurred to me that I should have been checking my Volvo Penta Users manual, not the Four Winns manual, which of course did not have this info. :oops:

Ray

rpengr · **Posted:** Tue Aug 06, 2013 9:12 am

Follow up:

Examining the plugs again, All of them had some charcoal grey paint, so I think they are the original plugs from 13 years ago!

I replaced the plugs with the new plugs of the same type (Champion Plugs RS12YC). Used Tef-Gel on the threads, and sprayed external metal with T-9.

www.iFourWinns.com

What spark plugs should I use

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