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Negative Earth Conversion

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AlamedaMGB

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Picked up a project '67 Midget on Saturday, so I guess I'm the new guy. I also have a 77 MGB and have been over on the MG forum for a while.

Question: I plan to convert to negative ground ( for sanity's sake ) and am wondering how the starter reacts.. I've seen no mention of it..

Also, There's a lot of things that are disconnected in the engine compartment, and I would like to get some close up pics of the engine compartment from all angles. Anyone here have any? or willing to run outside and take a few?

I'm familiar with MossMotors and VictoriaBritish for MG stuff.. Tony at TheAutoist says he has some Midget stock as well.. Other suggestions on suppliers?

I'll keep you updated on the progress.. It's going to start as a race to make it a running daily driver, and then update and restore as time and money permit.

Wish me luck.
 
Re: Newest Midget!

No starter problems converting to - grd.
Do check the operation of the heater blower when you convert as it might draw air out of the cockpit and blow it into the engine compartment. Ask me how I know /ubbthreads/images/graemlins/wink.gif
Watch the tach, it's electric an MUST ne converted or it will fry.
For parts Peter at World Wide Auto Parts in Madison, WI has most of the mechanicals, no chrome or rubber bits but suspension, brakes, engine, and hydraulics. OEM quality and no chinese made junk.
And then there is
Ed at Just Brits, Special Ed as we call him. He is a real character and he is a miserable cuss but he does know his brit iron and is a good source for parts.
 
Re: Newest Midget!

You sure it's a '67? The '67 I had was negative ground from the factory.
 
Re: Newest Midget!

You sure it's a '67? The '67 I had was negative ground from the factory.
Click to expand...

Yeah, I second that. I have a 1968 Healey Sprite that came as a negative ground from the factory. The Haynes manual that I have says that all of the models after the mid 60's came as negative grounds from the factory.

Ben
 
Re: Newest Midget!

'68 was the first year for Negative ground. The first commission number for Neg. ground was GAN 4 60460. Look at the tach. It will say whether it's positive or negative. I'm looking at a Tach from a '64, and it says RPM x 100, 4 cyl,
Positive Earth.
That's a # RVI 240I/00B tach.
Then, there are other dead giveaways, like the way the battery is wired. Or, whether or not it has the decal saying "Caution, this vehicle wired Negative earth."
Jeff
 
Re: Newest Midget!

Tach & fuel guage are pretty much the main concerns when converting ground. I converted to an alternator at the same time so I don't recall if the gen. would be a prob.
 
Re: Newest Midget!

Bugmike can you tell me more about the fuel gauge concern. I did the neg ground on my 59 and one of the problems I had was with the fuel gauge not working. I assumed the sender unit went bad. I was too lazy to pull the tank to repace it. Is there something that needs to be done in the gauge? Thanks
 
Re: Newest Midget!

Yup, I'm sure it's positive ground. thanks for the word of caution.
Battery connections and the label on the tach don't lie. And of course, there is no 'negative earth' sticker, so it MUST be positive ground, right?

I just want to get this running reliably first, so I'll just repolarize the generator, but I'm sure I'll switch it over to an alternator soon.

I don't mind converting the tach, but this is the first mention I've heard of the fuel gauge.

I've heard that some folks have had problems with their ignition points and fuel pump points going bad shortly after a conversion..
Anyone else experienced this??
 
Re: Newest Midget!

I changed a bunch of stuff when I did mine. I changed the old generator over to a neg ground Mitsubishi alternator and went with the Crane electronic ignition to eliminate the points problem. I have a newer electric tach that I am going to convert to neg ground soon. I don't know about the feul pump as mine is mechanical. I know the new SU pumps for sale are sold either neg or pos ground so there must be an internal difference. Hope this helps.
 
Re: Newest Midget!

Hello Al,

how is changing from positive to negative earth going to help your sanity? Unless you wish to fit a negative earth radio or the like, why bother?.
If you are set then do reverse the coil connections as that is polarity sensitive. (It will run cross connected but the spark is weaker at the plugs) Also in some cases it is necessary to turn the battery around to make the connections, this can be a problem if the batterry clamp is now close to the terminals as it can short the battery with dire consequences. The fuel gauge is not polarity sensitive.
Also some S.U. fuel pumps are polarity sensitive if they have diode suppression on the points but I don't think that should be the case with your car.

Alec
 
Re: Newest Midget!

I knew someone would ask..

A: All my other cars, including my MG's are negative ground
B: I would like to fit a new generation radio/accessories( after I put in an alternator)
C: Here's the biggie.. This will be my wife's commute car, and I don't want some friendly guy helping her with a 'jump start' after she leaves the lights on again and fry anything. Hence, the sanity..

Cheers.
 
Re: Newest Midget!

As I said, I made the conversion some time ago, so memory is a little hazy, but the problem I had with the fuel guage was that it read full when empty and vice-versa until the leads were switched (Does that make sense?).
 
Re: Newest Midget!

I made the swap when I brought my car back to life. Agree 100% with the tach (I went with a new one for time sake, but unhappy it doesn't match) and a aftermarket fuel pump.

I also had a HUGE problem with the alternator conversion. Went through 3 units to find one that would work in my 64 Sprite. I ended up and am happy with the AutoZone Duralast # 7140 (I called the store). Had repeated issues with the volt. reg not working and it even fried the battery once (before I knew I had a problem). This model is a one wire unit with a (working) internal voltage regulator.

Most items just get reversed as the above post mentioned about the heater blower. Coil / Battery / Heater / Fuel Pump (after mkt).

Replaced: Tach (I've read the post on how to convert and just found I couldn't follow it) & Upgraded to an Alt. for more juice and lower cost (more for less if you would think of it that way).

Same: Horn / Headlamps

I also upgraded the headlamps to halogen's. Used the Hella's (recommended from someone here on BCF) and they are great and look original.

Feel free to post any questions -- welcome to BCF !!

George Zeck
/ubbthreads/images/graemlins/hammer.gif
 
Re: Newest Midget!

I also had some problems with my alternator conversion. The Mitsubishi I got was a rebuilt unit that seemed like a good deal at $35. After hooking it up it fried my new Optima when it put out 14.5 volts. I had an auto electric repair shop fix it for $65. Not such a deal after all!
 
Re: Newest Midget!

Hello GH,
14.5 volts seems a reasonable output, Lucas's specification for the 17ACR alternator on my Triumph is 14.7 volts.

Alec
 
Re: Newest Midget!

It boiled the goop out of the top of my optima! What a mess. Thankfully the dealer I bought it from warrantied it. It is fine now.
 
Re: Newest Midget!

See Spritenuts post...........
Fuel guage IS NOT affected by the change in polarity.......
Alternator conversion DOES NOT use the voltage regulator. It is bypassed. You can gut a voltage regulator and rewire it if you want it in the engine compartment. Otherwise remove it and rewire the wires that connected to the voltage regulator.
Positive to Negative conversion see: https://www.mgcars.org.uk/midgetspriteclub/sprite/spriteposneg.htm

Alternator installation and Tach conversion see: https://members.tripod.com/PDLJMPR/techin.htm#Electrical:
 
Re: Newest Midget!

I forgot to mention that I did add relays for the headlamps & fuel pump. Very vital so you don't fry your 40 year old wiring.
 
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