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KRAVEN
03-12-2004, 01:13 PM
At what intervel do must replace spark plugs?I currently have 76 hrs on my original set and I am thinking about changing them at the beginning of this season.Any suggestions on brand?

HyperDonzi
03-12-2004, 03:22 PM
Most change them every year, some more than others. Spark plugs are really personal opinion (just what I have seen). I have had bad luck with Champions, and use NGK in everything from the boat to the weed whacker. The plug gap is on the top of the carb cover.

Iridium plugs, in my opinion are not worthwhile. You would be looking at over 50$ for JUST the plugs and you wont gain a tenth of a mph.

Tommy

Last Tango
03-12-2004, 04:24 PM
Kraven,
It might help to remind folks you are running a 377 Scorpion motor. I think your plugs are a whole lot different than the ones in my MX6.2MPi. I replace mine every year when I do the major service. I only have 100 hrs on my 2001 18 (built and delivered Aug 2000) but I have chosen to do a major service with new plugs every Spring. As for brand, I would stick to the same brand you pull out for now since you are still under warranty.

Last Tango
03-12-2004, 04:53 PM
Madpoodle,
I understand completely about the warranty thing. I only chose to offer caution because if he picked a BRAND over the correct replacement and something happened internally - Mercury/Z-Care may use that as an excuse to disallow certain otherwise covered repairs. I fully agree on fresh plugs, though. Can't hurt.

KRAVEN
03-12-2004, 05:03 PM
Thanks fo the info regarding plugs.This was the first season that I winterized the boat and thought it would make sense to replace the plugs since I fogged the motor in the fall.I am sure I will use the same plug I pull out since I agree with the Zcare warrinty issues.The season is fast approaching and will be getting her shipshape on our return from Jamiaca. :)

HyperDonzi
03-12-2004, 05:06 PM
Also may want to look at replacing the wires. We left ours on for 2 seasons, by the end of the season (with new plugs) 4600RPM was all it had. New wires brought it back to 5000.

Murphy
03-12-2004, 05:08 PM
You may want to try extended length (nose) plugs. These are not commonly seen outside the high performance circuit, but willl improve performance of a stock engine. The insulator and tip extend further into the chamber, improving ignition. Check your clearance at TDC just to be safe. They generally come in 3 lengths, are available in most brands and at most parts counters. Don't waste money on the split tip, dual spark, or whatever they call them. Gap them right, replace annually and run.

Murph

BUIZILLA
03-12-2004, 05:45 PM
IMO, you won't gain a thing with ext reach plugs in a low compression engine, especially with dish pistons. Also the long reach noses are commonly for large gap ignitions of .045-.060. You would be better served by indexing the correct electrodes with the open arc flame facing the exhaust valve.

J

Cuda
03-12-2004, 06:49 PM
I change mine whenever one engine is removed for transmission work. :bawling:

Murphy
03-12-2004, 07:58 PM
"Spark plugs are one of the few devices in the ignition system where a measurable increase in performance, fuel economy, and durability can actually be achieved. Despite claims to the contrary, performance gains are not because of breakthroughs in spark plug design. Since the four cycle engine was designed over 100 years ago, the basic spark plug configuration has changed little nor has it been improved upon much at all.

The increase in performance comes from switching from a standard nonprojected nose to a projected nose plug. Most professional high performance marine engine builders and tuners automatically switch to projected nose plugs as a matter of course, but for some reason this is still a big secret to a lot of amateur or backyard builders. Most are unaware that these projected nose plugs can be purchased at just about any common auto parts store and they cost no more than standard plugs.

Projected nose plugs are more efficient at igniting the air/fuel mixture because the nose of the plug projects deeper into the combustion chamber. This has the same effect as advancing the timing a small amount and also decreases detonation slightly. When comparing a standard nose plug to the new style heavily advertised (split ground) it soon becomes apparent that the new style "unconventional" design is actually a projected nose plug.

Dennis Moore (my hero) in Small Block Chevy Marine Performance

I'm running small chamber (60cc) double-hump heads with 2.20 intakes and 1.60 exhaust valves. The block is decked and setup with quench pistions to produce 9.5:1 compression. Given that cost is a wash, I guess the question regarding extended nose plugs in any engine is "what do you have to lose"?

Murph

Rootsy
03-12-2004, 08:49 PM
I run good ole R43TS AC Delco in the sbc... i've run bosch and i've run NGK and i've run Champion and none gave me any performance gain. So i run AC Delco... #1 it is easily available... #2 i've NEVER had one fail... i do run an extended tip just for ****s and giggles... plus i run an MSD ignition with a 0.055 plug gap... my dynamic CR is right around 8.5:1 with my camshaft as installed and my static is 9.4:1 on a dished piston with a vortec style combustion chamber. I wholeheartedly agree with Jim about indexing vs the extended reach.. unless you have a severely shrouded plug for whatever reason.

now... for everyone that says champion sucks... the little mouse in the camaro made the most HP and torque with the champs than with the other plugs we ran which well were about everything.. cept denso's. Champ, AC, Autolite, NGK, Accel, Splitfire... 632 hp @ 7800 rpm on a sbc with factory cylinder head castings (extensively recontoured ports of STOCK volume) and stock static CR isn't bad... through 1.94 / 1.50 valves and a 4MV Quadrajet (untouched venturis) :D

this summer i WOULD like to get my hands on some DENSO plugs to try... you figure since i work for DENSO i would be able to just GET SOME... fat chance of that... so where do i buy them?

Dennis Moore
03-12-2004, 09:10 PM
Murphy
Thanks for the compliment.
Dennis Moore
626-357-3573
www.mooreperformance.org

Murphy
03-12-2004, 09:36 PM
Holy Sh-- Dennis Moore has entered the building. Hi Dennis and welcome to the Registry.

Murph

BUIZILLA
03-12-2004, 09:49 PM
Roots, the DENSO plugs are the MacDaddy deal. Hard to find sometimes, as I have only one place down here to get them. Best for blown and real high compression n/a engines, easiest to color read the electrode for timing and ceramics for mixture. I swear by them in my Mighty Mouse @14.95-1 comp. Also, the #10 AC's work well, but there are two #10's available, each has a different center pin. The #10 number color is either red or blue on the box, to determine which is which center pin style. Confusing as hell.

J

MOP
03-12-2004, 10:01 PM
How many have seen the ones Ford are using in the new gas trucks. Single hoop looks arching over the electrode looked machined one piece in an add I caught today. I only fooled with indexing on two engines to me it is worth the time.