PDA

View Full Version : Spark plugs??? Big Grizz??



Tidbart
09-21-2002, 11:32 AM
If I remember correctly, when we spoke at Eufala about spark plug, you said NGK tested a lot of engines and came out with their own list and recommended gaps.

I found the NGK plugs for my 18, BPR6EFS. Believe me they weren't easy to find for some reason. NGK recommended this part number for my boat with a .045 gap on their web site. I also found the same plug number and gap in my Merc Service Manual.

I installed the plugs per spec and needless to say, half way throught the installation I moved a rag off the top of the engine and there staring me in the eye was the spec of .035 gap. :confused:

Well, I wasn't about to stop, so I completed the install.

What are your thoughts on this and what are the ramifications of too big/too small a gap in the plug??? :confused: Your input as well as any others would be appreciated.

Thanks, Bob

Greg K
09-21-2002, 12:26 PM
Monarch Products (http://www.sparkplugs.com) Great place to get plugs with practically every NGK plug available in stock always and best prices. Plus Denso, Autolite and Champions.

MOP
09-21-2002, 01:06 PM
My 2c If you have hot ignition you can go wide on the gap. I run 50 on my 4X4 with Jacobs over two years now no prob.

Tidbart
09-21-2002, 01:23 PM
Thanks Greg, they were my next choice if I didn't find them locally.

MOP, what exactly do you mean by "hot ignition"?

Bob

BigGrizzly
09-21-2002, 05:11 PM
Here is the deal, Wider gaps fire a leaner mixture better and gives a more even burning. The narrower gap burns a richer mixture better with less fouling. At 0.035 or 0.045 you won't see or feel the difference. The only thing you will need to do is check nore often. Point being in the early 1970 with emissions on the upswing many cars were using hight output coils and gapping at 0.040 to0.060 and running a lean condition to make the emissions numbers. I f you look now most are arounf 0.040-give or take. My engine runs 0.040 gaps. And afterhours of dyno testing and doing the spark plug dance from0.028 to 0.060 not one Hp difference was shown and very little exhaust temp difference! I settled on 0.040 because, as you have heard, I have a very low idle so that gap works to my advantage because I run lean there.
MOP means hotter being more volts so he can by theory run a wider gap as mention by the 1970's comparision. Does it help there isn't enough time in a day to discuss this.

MOP
09-21-2002, 05:40 PM
Bravo! With middle of the road gap you can't go wrong.

Tidbart
09-21-2002, 08:18 PM
Thanks guys,
With the mpi I have, I would bet the ECM will compensate for any lean/rich condition it will encounter. I will stick with the .045 that I put in and see how it goes.
I really wanted to hear that I didn't have to back and do it again. I think sweated off 5 lbs working in this damn sun. :D
Thanks again,
Bob

knee deep
09-21-2002, 08:47 PM
I bought Autolites that were gapped at 45 and the gal at the shop told me the gap was supposed to be 35. Engine is a 351W. I'm sure the timing is off and the boat won't come onto plan. I need to redo the timing should I increase the gap? It sure smells like its running rich.

BigGrizzly
09-22-2002, 08:50 AM
NO, gap isn't your problem. Like I said you won't notice the difference. Plug makers do a generic gap at the factory and are not accurate- this saves production costs. Use recomended gaps form the plugs maker or engine manufacturer either is fine don't get creative unless you have the equipment or knowlege to do so!
Timing is more important than a few thousanths of plug gap.

HyperDonzi
09-22-2002, 06:38 PM
This is weird, I decided to do a speech on how to gap spark plugs. Now i have an excuse to be here when I'm doing "research."