I got a nicely made woven ground strap for my mostly 1923 Runabout from one of the Model T suppliers but never put it on because it seemed to be too short to fit comfortably. It is 7.5" from the center of the battery post to the center of the hole that mounts it to the frame. Is this right? It seems to tight.
You don't say how long the ground strap is, but for 6V operation I would say as short as possible and heave as possible.
1. Get a good clean connection from the Neg (-) battery terminal to a shinny spot on the frame, (Avoid going through 90 year old rivet joints.)
2 Install another ground cable from the frame (a shinny connection) to a starter bolt
3. Use heavy (#0) cable.. NAPA has it and i bet our venders do too.
Six Volt systems work great if maintained. Your coils won't work as good on 6v so make sure your mag is in good shape.
To do the above, a 7 inch cable is too short.
Am I preaching to the choir?
Take a look at the link to this thread. Some good advice there.
Ford specs, ground cable is 9".
I'll add my 2 cents here. My '27 was a really slow cranker. Starter was checked/re-habbed by me. I had the rear floor off for some maintenance one day and started the car. That's when I spotted the braided cable smoking. It looked fine but wasn't. (connections were good/cleaned). I lost it and went to a "modern". Cranked faster after that.
I called around local auto parts stores to see who might have a heavy duty 6v ground strap longer than the one I had and found that of the places that were answering the phone a day or two after Christmas, NO ONE EVEN KNEW WHAT I WAS ASKING FOR. One snippy young fellow even said something about upgrading to the heavier 12v cable he had in stock . . .
My last call was to Dave at Chaffin. I asked about the 7.5" size and he said that this is the correct size if the battery is made with the negative terminal at the left rear. I have the Optima and had mounted it on the other side of the battery carrier for reasons I have long since forgotten.
OK, the old 12v cable was removed and while it was in great shape, it mounted to a rusty bolt on the front battery carrier mount. The stock bolt was used and it was too short so only some of the threads were gripped by the nut. Altogether, the cable was small and poorly mounted.
The new 6v short strap was mounted to the rear mount as Ford did it. I needed a longer bolt and used a stainless bolt, nut & lock washer. The Dremel enlarged the mounting hole on the ground strap and cleaned the paint off the outside of the frame rail so that the head of the bolt would get good solid contact. The strap itself was mounted to the inside of the frame rail. If I had it to do over again I would see if it would stretch around to the outside where the lugs entire surface could make contact with the frame.
The Optima was remounted to the frame rail side of the carrier.
After the terminals & posts were cleaned and everything was strapped down properly the starter button was pressed and the difference was obvious. The starter DID spin the engine faster and the engine "caught" much sooner than before. I don't want to make too much of this, it did not spin like it used to on 12v but it is faster and is probably now in the norm for a Model T.
Speculation - I noticed in the Restoration Supply Co. catalog that they sell a battery terminal with two positions on it. With the #0 & #00 cable & ends they also sell a custom two ground strap could easily be made up, one end to each battery mount on the outside of the frame. I wonder if this might make any further improvement?
This also opens up a second bit of speculation - the battery carrier will take TWO Optima batteries. While I have never run down the Optima I have now, I wonder if a second one along side of the first one and wired to it might be even better? At over $200 a pop I'm not likely to find out but I would be curious to know . . .
Read my comment on Ron Pattersons post. That should answer your question.
Larry - I just read your comments and they didn't seem to address either the dual ground or dual battery question. Did I miss something?
Vintage Paul, baffled - normal for me . . .