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Old 03-09-2010, 08:19 PM
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Bettery ground to engine or chassis?

I'm building a car with a fiberglass body. My battery will be in the trunk. I have a 4 AWG braided ground strap for the engine to frame connection. Do I need to bring my battery negative cable all the way up front to connect directly to the engine block... or, can I connect the battery negative cable to the frame near the trunk area? Thanks...

Mike

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Old 03-09-2010, 08:31 PM
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Run a heavy ground strap from the engine (I usually use battery cable from starter mount or belhousing bolt to a close clean bolt on frame). Then ground the battery to the frame with a short cable. A good ground is accomplished.

Then run a frame grounded electrical bar near fuse box to ground all wired devices.
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Old 03-09-2010, 11:42 PM
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I started my 'plastic' car with a ground from the battery to the frame. Then double grounds from the motor to the frame. #2 cables. Grinder ground bare spots on the frame and motor. No grounds to aluminum heads.

"Plastic" cars will have grounds everywhere. You will need several ground terminal strips through out the car. Wiring can be a real challenge with all the ground wires. Resist the temptation to stack grounds on a single terminal. It can be tough to run down a problem with this method.
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Old 03-10-2010, 06:52 AM
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The frame can be used as a ground, but for optimum performance it is best to run a properly sized ground conductor from battery (-) directly to the engine block. On my glass car I did that along with a remote starter solenoid in the trunk. That way I do not have a constant hot heavy battery cable running from the battery all the way to the front of the car. I then ran a #10 ground conductor to a terminal strip in the trunk for grounds at the rear of the car. Another #10 ground conductor to another terminal strip under dash for interior ground connections. Frame is also grounded at engine and battery (-). You can never have enough ground points and should NEVER DEPEND ONLY ON THE FRAME FOR GROUNDING IN ANY CAR.

Vince
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Old 03-10-2010, 06:59 AM
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You got that right especially with 'plastic' cars.
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Old 03-10-2010, 07:14 AM
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Quote:
Originally Posted by bentwings
No grounds to aluminum heads.
Why do you say no grounds to aluminum heads? I thought heads should be grounded to the block with a single strap on each one. Then block grounded to chassie with heavy grounding cable.
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Old 03-10-2010, 08:23 AM
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Aluminum oxide forms immediately on the surface. It is a good insulator. Unless you can get under the surface and stay there you will not have a good ground. An anodized surface is even better. And a hard anodized surface is even better than that.

Yes you will probably get a 'ground' for higher loads but if you have some low current electronics as many of todays stuff is you are in questionable area. Sometimes you simply can't get away from it like temp senders and various intake sensors.

Just keep it in mind.
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Old 03-10-2010, 11:29 AM
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I was just wondering why, thanks. But the electric co. doesn't seem to have any problem by using the compound on the services comming into most homes. Seems that a good clean strong mechanical connection should have no problem mataining a ground connection. I would think the advantages of some ground are better than no ground connection at all.
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Old 03-10-2010, 06:07 PM
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The electrical service that comes in as aluminum is bonded to the house copper with heavy impact compression fittings and do not loosen over time. I watched as the service was hooked up to our new house years ago. The electrician used a clamping device then loaded what looked like a 38 special blank into it and hit the end of it with a hammer. Oh and he did this hot , one phase at a time.

Vince
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Old 03-10-2010, 06:21 PM
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Quote:
Originally Posted by bentwings
An anodized surface is even better. And a hard anodized surface is even better than that.
Just so it's clear- the "better" means "better insulated", not "better conductor".
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Old 03-10-2010, 06:44 PM
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Quote:
Originally Posted by 302 Z28
The electrical service that comes in as aluminum is bonded to the house copper with heavy impact compression fittings and do not loosen over time. I watched as the service was hooked up to our new house years ago. The electrician used a clamping device then loaded what looked like a 38 special blank into it and hit the end of it with a hammer. Oh and he did this hot , one phase at a time.

Vince
In Michigan they just tighten down with a large breaker bar squashing the conductors into the lugs.
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Old 03-10-2010, 09:14 PM
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Cobalt You are right.
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Old 03-10-2010, 09:28 PM
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The battery relocation kits that are sold at Summit and Jegs come with a 20 foot positive cable and a 3 foot negative cable. I don't understand why a reputable company would sell a kit that has you mount the negative cable to the chassis in the trunk instead of selling two 20 foot cables (other than keeping the price down)? Is there any situation where just have a chassis ground in the trunk is sufficient?

Mike
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Old 03-10-2010, 09:51 PM
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''All'' the cars I built for myself and for other people, I aways put the battery in the trunk..Run a hot to a disconnect switch and then to the starter, And a ground from the battery to the frame, and a ground from the motor to the frame. and never had one problem. not once.. I weld a bolt to the frame to bolt to, I never just use a bolt..
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Old 03-11-2010, 11:45 AM
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Getting back to the reply that 302 Z28 made regarding a remote solenoid in the trunk....
Vince, how does the remote solenoid work if you have a GM or Mopar starter with integral solenoid? I can see how it would work for Ford motors since those are, for the most part, mounted remotely anyway. How would you wire up a solenoid to a solenoid? If they are wired in parallel to the ignition switch, then when the key is turned, both solenoids would be energized at the same time, which would kick in the starter motor? It sounds like it would work, or am I off base here? Can the starter mounted solenoid be bypassed entirely and just the remote one used?
I'm putting my battery in the trunk of my fiberglass car and have the same questions. I've also seen other posts that mentioned running a remote solenoid so that the primary battery-to-starter cable is not hot all of the time.
Incidentally, I asked this exact question at car shows to reps from both Painless Wiring and American Autowire..According to the blank look on their faces, it was like they never heard of such a thing....

Thanks,
Steve
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