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Boat Nut
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Discussion Starter #1
Grounding Aluminum heads to iron blocks? I heard this from several sources as a must do item. Thing is I've never seen it done, soo is it urban myth or is there something to it?
 

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I've never done it.. The one thing I will do is run a ground wire from the block to where ever the main battery ground is.. Bad grounds can wreck havoc with MSDs..
 

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When you run abunch of head bolts through it, I'd assume that would be a proper ground.

Jerry
Agreed X the number of head bolts you have!
Not to say this in any way applies to alot of boats, but lets take mine as a example. Head studs set in lock tight or any kind if sealer. Not exactly conducive to the flow of electrical current, specially a low amp current draw like a ignition system, specially at low Rs. I am guessing less than 1 amp at idle for a MSD. Even less at the spark plug. Then throw on some FelPro MLS Stainless VITON coated head gaskets. Lets see, viton rubber coating on top of the worse metal imaginable for conducting electrical current. Mmmmm? Oh but wait, we still have the manifold, which the only contact with the block has a 1/4" of silicone between it.
Now imagine trying to get one amp of current to flow thru that! Not saying it won't, but when you know how much a head dances around on a motor, and can see the brinelling on the head, I feel much better with a small little # 10 wire from even one head to the block. Its easy, and it elevates one possible problem.


Doesn't everyone use their motor as the main ground in a boat? Where else is there?...
Nope. Never. Too much vibration going on. One large cable from the battery to the block for the starter only. EVERYTHING else back to the battery, or a junction lug on a seperate cable from the battery. Like this:


Using the block as a junction block is not the best setup.



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The only time I have ever heard of that happening is with electronics like a data recorder, or a CPU/ECM for EFI, or something on that order. Never with plain electo-mechanical stuff. Possibly a tach, specifically a play back type, but I have never heard of it. All my electronic stuff like data recorders, or O2 sensor/recorder specify a seperate ground, even to a terminal strip. they don't even want you stacking grounds on a single lug.



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Just for fun (must be bored), I went and checked resistance from head to block and there was 0 resistance.
Alum heads, Cometic MLS, bolts with sealant.

I would never use the head as the main ground, I just can't figure out why you would run an additional ground to the head? I have used the head as a ground for dual sync EFI distributors, solenoids, w/t senders, and intake manifold (obviously bolted to the heads with no block attachment other than the distributor) for IAT sensors, manifold surface sensors, etc. and never had a problem. Not saying under the right (or wrong) circumstance it couldn't cause a problem, just never seen it happen....
 

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Boat Nut
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Discussion Starter #10
Strange things happen when you apply current/voltage to poor conductors, that may otherwise seem ok. ARP black oxide studs, Cometic gaskets, ARP assembly lube, and teflon paste. Engine getting hot to cold, will do it's fare share of moving around. Galvanic corrosion
 

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Just for fun (must be bored), I went and checked resistance from head to block and there was 0 resistance.
Alum heads, Cometic MLS, bolts with sealant.
Like I said, it doesn't apply to alot of boats, and may never cause an issue. But it just to easy to run a single wire from the head to the block. Detroit did it on more than a few engines. Usually at the back of the head to the chassis.

Black Oxide and anodize are by far the two most over looked barriers in a boat.



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Like putting the ground on the block and welding on the headers. Thats how I discovered it.
Absolutely true..... Now compare the ground requirement of a 220 volt welder to a 12 volt negative ground system. :D

You really did that??? :|err:D:D
 

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No. But lets remember, voltage is what "pushes" the current thru any resistance. Now compare 12v to 220. And, keep in mind, a tig doesn't have 220 at the tungsten.

I would be much more concerned about a injector firing correctly than say a plug. The only reason a plug because an issue is it is continually gaining resistence to ground as the rpm and boost if applicable. Between wires, plug condition, and operating conditions, why give it any more to deal with.

Again Brain, not saying it has to be done. Like gaapping a plug. How much difference is there between .030, and .040. Maybe .040 is just enough to misfire here and there on your deal. But yet, everyone gets out the gapper.



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Strange things happen when you apply current/voltage to poor conductors, that may otherwise seem ok. ARP black oxide studs, Cometic gaskets, ARP assembly lube, and teflon paste. Engine getting hot to cold, will do it's fare share of moving around. Galvanic corrosion
Soooooo...are we talking about the same kind of corrosion one would run anodes for? If so your thinking the anodes arent enough??
Edit...never mind ...just reread this and it looks like this thread is more about electrical that anything....my bad.
 

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Water isn't the best grounding location, but water running through block to heads and then out would create some sort of ground.
 

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Water isn't the best grounding location, but water running through block to heads and then out would create some sort of ground.
Actually Jim, its a horrible conductor, specially fresh water. Salt is considerably better, but still worthless.
Try this, disconnect you battery, and run a stream of fresh water from you garden hose right on to the ground lug, and hold the ground cable into the stream, and see if you can even light your dome light. Not start you engine, just light the smallest bulb in your car.



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