'64 XKE OTS

[Heuer]

The easy way to tell whether you have pos or neg earth is simply to look at the terminals. The pos terminal is bigger. Put a battery in the hole & the terminals will only go on one way.

Obviously you have not worked with or have experience of the original Lucas FRV117A battery and helmet connectors - terminals are all the same size! Owners also swap the -ve and +ve cables over so the battery terminals are facing the outside for ease of access.

[Hugo]

That's odd. I actually have a lot of experience of these 'helmet' terminals; BMC cars used them a lot, and I used to work on them many years ago. And I'm sure they were different sizes - the caps were marked + and -. They had a habit of the screws bottoming out and they would then make contact solely via the screw.
So what is happening - is my memory playing tricks or did they change? Actually the right-hand terminal in your pic looks bigger - I presume that is a trick of the light?

[Heuer]

Trick of the light. Besides, the clamp style lugs if used would work on different sized terminals because they can open up. On the 3.8 E-Type the die cast lugs and cables looked like this:





For the -ve earth 4.2 cars there was a yellow sleeve over part of the earth cable matching the colour of the polarity warning plate.

[Hugo]

Yes, the clamp type will open up, but you can always see if that has been done. As I said before, I don't like this 'helmet' type of terminal, because they can give problems. And if they are the same size, that's another reason not to like them ;)

[Heuer]

Lucas clearly disagreed with you and stopped making the clamp lugs in favour of the die cast 'helmet' lugs:


http://mgaguru.com/mgtech/books/lts_otc ... attery.pdf

[Hugo]

You know why, don't you? This was to counter-act the corrosion of the positive terminal that used to occur with positive earth systems. When I used to work at a BMC dealership many years ago we regularly used to have to boil a kettle & pour hot water over the battery terminals to get rid of all the corrosion that used to grow on them. When they went back to negative earth the problem went away. That tells you how long ago that was! We had problems with the 'helmet' terminals also, as they didn't clamp as well as the clamp-on terminals.

[valley7]

All, thanks for the great info and help.

I do intend on keeping the car as original as possible. Other than the trans rebuild, some engine work (notes say it has a 4.2L oil pan and pump, was this common?) and repaint it is a survivor with just over 20k miles. It hasn't actually been used as a regular driver since the mid 70's. My Dad drove it around our neighborhood occasionally in the early 90's. He was collecting parts for a restoration, but trying to keep it as original as possible was intimidating. Once I see if I can get her fired up (and find all the parts) I'll have to assess what it would take to do this restoration properly or if it's best passing the project on to someone else.

In the meantime looks like I should be clear to toss my current battery cables (lugs are cracked and not the helmet style) in favor of something functional and color coded. Any other parts I take off will be labeled and kept. As far as the polarity discussion goes, I should be good to go. There's no radio in the car right now to damage (radio console has a gap), so it's probably in a box of parts somewhere. :-)

I'll report back on the gearbox as well, I was afraid to go after it too much not knowing the cause.

Stephen

[valley7]

Ok, I have an update...

1. The car is positive earth. I used an ohm meter and found that the chassis terminal had continuity to "B" on the regulator module (R340). This matches the schematic for positive earth. If the car had been converted to negative earth I would have expected the polarity to be flipped. (Edit, I previously called the chassis terminal negative, which was unknown prior to the test)

2. Engine cranks good, ignition light near tach comes on but no spark (all plugs pulled and sitting on valve cover). Next is to check coil power and then points. Maybe check compression to make sure rings are holding while I have the plugs out.




3. I got to the top of the gearbox but didn't take the shifter off. Noticed some very sloppy welding around the floor pans. I am guessing that the transmission rebuild from the 70's involved some very tacky sheet metal work to avoid pulling the engine out.... see the pictures. It looks like the floor pan was cut all the way around the transmission / belle housing with a die grinder and then riveted & MIG welded back together. When I get into the gearbox, I'll probably start a new post with a complete description and pictures of resolution.

[Hugo]

I wouldn't worry about doing compression tests at this stage. I would get it running first & give it a bit of time for everything to settle in & blow the cobwebs out.
Out of interest, would it not have been easier to do a continuity test (or rather measure the resistance) between the pos terminal and the chassis in order to establish polarity?

[valley7]

Hugo,

The question of which is positive terminal remained. No color or marking of any kind. (Edit: Sorry, original post should have said tested the terminal I assumed to be negative. It was the non-chassis terminal.)

I figured the deciding factor would be a device that was polarity sensitive (like the regulator) and matching it to the schematic. So if the "B" terminal went back to the chassis, it would have been negative earth and if it went to the other battery cable, positive earth. In this case it didn't go to the chassis, ergo positive earth.

I have a 1951 tractor that's positive earth. if anyone is wondering what happens if the battery is put in backwards, I'll test it on that rather than the XKE.

Stephen

[Hugo]

I didn't know regulators had a 'B' terminal. Normally they are F.A.D.E. (or A1 & A2). You do have a dynamo/ generator, don't you? Voltage regulators aren't polarity sensitive - they will work either way round. The coil sort of is - it will work either way but is less efficient the 'wrong' way. Unless it has a suppressor attached, then it probably won't work. Clocks don't usually work the 'wrong' way. Other than that, you just have to re-polarise the dynamo by flashing a live (pos) lead to the field windings a couple of times. Even if you forget to do that, it will soon re-polarise itself - the ammeter will bounce around like crazy for a few seconds till it all sorts itself out. You can't do stuff like that with electronics!

[valley7]

I definitely have a "B" terminal on a Lucas R340 regulator and a dynamo. I neglected to take a picture of the terminals. Next time I'm working on it I will get one.

The immediate problem with the gearbox is solved. I posted a separate thread on that with some extra pictures.

Some filing on the points and the plugs are firing away. I've seen some lawnmowers with a bigger spark, but should be enough to fire up and see what else the engine needs.

Next steps:

1. Take valve covers off and oil valves. Looks like there are some other misc areas that require oiling (I noticed oil location on distributor while I was filing the points).

2. Take carbs off and spray all the jets clean, hook up temp fuel line

Stephen