a plug is a plug?

floater212

here's my dilemma... my 2005 350mpi uses the ac 41-932 plugs which around here are hard to come by and very expensive, I hear the ac 41-993 are the new version and I can get them almost anywhere. are they the same or which plugs would you run?  here's the kicker... I e-mailed ACDelco.com and asked them, it's the world wide site and they said " not sure you'll have to contact the nearest dealer." what kind of answer is that?  thanks, jim l.

JoeStang

Skip ACDelco and call or email Merc. They should have the alternate spark plugs to use.

212rowboat

plugs make all the difference in the world.....

don't be fooled by semi-precious or exotic metals, they are SOMETIMES better, and oftentimes NOT... it all depends on the heat range and the bowl design of the cylinder...

hotter plugs are fine for cooler running engines... cooler plugs are better for hotter running engines.. it's all about controlling ignition- you don't want the a/f load in the cylinder firing off of a red hot plug tip, or off of a hot valve- you don't want a 'slow ignition' either, which happens when a plug only ignites a portion of the a/f load and relies on a portion to ignite the rest... you want an even ignition at a precisely controlled moment...

Al has said in the past that these engines like iridium... personally, I like good ol' copper with a wider surface than the pin-point style of iridium.. either way, check with the OE and run what the engine was designed to run... I say again: check with the OE and run what the engine was designed to run... (Al's opinion I highly value... and it makes sense, as these engines operate at or just above 165*f, which means you can more than get by with running an iridium plug with a fine point tip, as the cylinder is likely not hot enough to pre-detonate an a/f load all by itself).

off the cuff, however... if you want to improve power, economy, and control: use an iridium plug gapped around .060 and replace your coil with one that produces 45K+ volts... also, index the plugs, which is an old rodder trick that has been validated many many times: make sure the gap of the plug points toward the open portion of the heads bowl- it will ignite more readily and cool more rapidly.

floater212

just found a MERCURY SERVICE BULLETIN  #2006-03 that clarifies the plug change to AC 41-993. thanks all!

jreau

Drewactual, when you said "make sure the gap of the plug points toward the open portion of the head bowl" ? What is the open portion of the head bowl?

l-skynyrd

I get my plugs from Summit Racing Online. decent price, no sales tax and only takes a few days

and delivered to you door. They do have the AC 41-993.

Len

Black_Diamond

I just bought 16 of those. About $6.50 each at Autozone. Just need time to nestle into the engine compartment.

212rowboat

jreau said:

Drewactual, when you said "make sure the gap of the plug points toward the open portion of the head bowl" ? What is the open portion of the head bowl?

The dudes finger is almost atop the plug boss.. imagine the design of a plug electrode-to-shank.. indexing the plug to where the open gap is pointing toward the open part of the bowl (bowl being top of combustion chamber), and imagine how much easier and certain ignition is when indexed that way.. that is a simple thing that increases power and economy.

Black_Diamond

Looks doable, have to put a mark on the plug to know its orientation and fuss with how tight you go. Just the position of the thread start could make this hard I'd think?

212rowboat

You'll need a few more plugs than usual, and will have to move them from cylinder to cylinder to be perfectly right.. just having the gap NOT pointing to the head is the most important part, and that gives you a roughly 140* margin of error..

212rowboat

Or rely on the squeeze for ignition, huh diesel dude? :-)

212rowboat

There are a lot of parts on a diesel compared to a gasser, and the expense of repair is much greater, if for nothing but hiring a diesel mechanic.. they both have their place..

I'm looking at buying two 30kw generators fired by Detroit diesels at an online military auction, for (dig this) <$100 each.. I'll then hire a Marine who works on them for a living to go through them and repair/service them.. afterwards, I'll implement automatic transfer switches to them both, put one on a skid with a tank, and sell it for enough to cover the the cost of outfitting them, and use the other for home back up power..

In that application, diesels can't be beat.. as far as smaller and easier powerplants, I'll take a gasser..

212rowboat

Google govt drmo auctions.. govt liquidators, or something like that.. drill down to north Carolina, then camp Lejeune, cherry point, and fort Bragg.. look for the gennies.. they aren't on axles, these are skids. They're $25 bid right now (opening bid) but watching them in the past tells me the price will be sub $100..

These don't have axles.. there are others that do, but are generally <20kW systems.. keep your consumption low during a power outage and you can get by with the lighter ones..

I live between cherry point and camp Lejeune, about twenty minutes on either side of me.. driving over and sweet talking a marine on a skid steer to load it is easy for me, not so Mich for folks out of the area.. if you're in the market, though, it would be much cheaper to swoop down from Maryland and get one as opposed to buying local, no? .. another key: I have a slew of local marines who work on these things for a living and have access to parts, that I can hire on the side for a few cases of beer.. :-)

212rowboat

Oh.. look for the set that have 1k hours or so on them.. these were likely new, went to sand box for a tour (six months or so), and shipped back unclaimed by whatever unit that owned them..

212rowboat

RinkerYan said:

Have you seen the Bosch Platinum plugs with the 4 electrodes? Or the E3 Plug? Eliminates the orientation issues.

Depends.. on standard two valve heads, which a lot of marine heads are, the plug boss is under the valves in relation to the vertical cylinder... Four valves and the plugs you mentioned are fine.. with two valves it creates the orientation issue.