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MG MGA - Battert grounding point/bolt

Greetings all,

Well, I'm to the point on the coupe restoration that I just need to complete a very few last items. One that has me stumped at the moment is the gounding point for the battery. I know where it's located but that attachment hole is only 1/4" deep? The old bolt must have broken off and I'm just now finding that out! Not sure how to get a drill in there to fix this...but I hope to figure that out. I need to drill and tap that location. I tried the mounting point where the exhaust hanger is attached to the frame but that is not heavy enough enough to pull the starter current. What size bolt/thread was used?



Robert Maupin

Curious. What point are you talking about where the bolt is broken?

The ground cable does normally attach to frame at a through hole near the center exhaust hanger (bolt and nut). It will carry plenty of current. For lots of newer cars the ground cable is attached to body sheet metal.
Barney Gaylord

Greetings Barney!

The hole I can locate is adjacent to the exhaust pipe hanger attachement plate, just below and aft the cross-over frame support tube (that the battery frames are welded to.

As I mentioned, the hole that is there is only about 1/4" in depth and I can't see any "through hole"????

Robert Maupin

I have a 58 coupe. I'm using a single 12V battery in the RH battery box. My ground cable is attached with a thru bolt through a hole drilled in the support rib of the battery box. Works just fine.
G T Foster

This is from a roadster. Hope the picture helps.



Having now identified the correct earth strap fixing position for your battery, do now consider the not very difficult but extremely effective improvement job of running an additional cable (starter size heavy current cable, that is) from the earthing bolt you have been discussing to one of the starter motor fixing bolts. It is easy to do and the route from rear to front is obvious. A good quality cable and suitably sized terminals soldered or crimped (heavy duty) at each end is all that is required. This way you can forget about most, if not all, future poor earth connections via the chassis and/or bodywork of your car. You will have a negative polarity path effectively directly from battery to starter motor, and on to other electrical items, equivalent to that of the positive path. A worthwhile add-on in my view.
Bruce Mayo

Thanks Barney for the heads-up on the correct earthing point. I had mine attached to the vertical wooden attachment bolt as shown in Larry's photo above. I have now reattached to the bracket as you describe.

Steve Gyles

O.K., I found what I consider a good grounding point using one of the pass through bolts on the left rear shock....all set to start the car. Now, when I pull the starter switch, nothing.....except some smoke and sizzle coming from the left battery....and the cables get warm as well What do you folks think I'm doing incorrectly? Eager to get this one on the raod....


Robert Maupin

Robert is your car positive or negative ground?

Any pictures may let us help you.

Oh, I forgot to add two other apsects to my probelm.

A) When I turn the key, the ignition light comes on and the fuel pumps kicks in beautifully and runs until primed.... and

B) When I pull the starter knob, the ignition light goes out....then comes the smoke and sizzle....?

Thanks again...

Robert Maupin

It sounds like you have not fitted the cable that joins the top and bottom of the left hand side engine mount.
This cable bypasses the rubber section of the engine mount.
It must be a heavy current type cable capable of carrying the full starter motor current.

M F Anderson

Are your battery clamp bolts long enough!
Mike (lol)
Mike Ellsmore

Sounds like a poor connection at the battery terminal- arcing and high current draw. Clean the terminals and connectors real well with a wire brush. I use a battery corrosion prevention spray to keep the terminals from oxidizing when it's laid up for winter.
Mark J Michalak

Could be a broken or high resistance connection inside the battery if "smoke and sizzle" comes from one of the batteries. Another possibility is a short circuit in the starter motor. Try disconnecting the on-board battery and substituting it with a known good 12v battery via jump leads. If you still don't turn the starter, then the fault lies with the starter or its wiring.
Lindsay Sampford

Mike, the hold down clamp in the picture is from the local auto parts store. It's one size fits all. The bolt length was trimmed back just after the picture was taken

This thread was discussed between 04/03/2011 and 07/03/2011

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