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MG MGB Technical - Starting after 2 years down

I just started my 79MGB after it was sitting for 2 years.

First I drained the oil and refiled. One quart I pored into the oil tube that goes up in the oil filer than put the filter on. I took the coil wire off and turned it over until I got good oil pressure.

Then I put the coil wire back and it started right away.

I have 2 questions though.

First my oil pressure at idle was a little over 50 when I reved up the engine it went to a Little over 75

Is this normal?

The second question is since I rewired the car completely I converted it to a GM alternator. Now both the gage and my Multi meter read about 14 volts.

Is this to high?
RSF Bob Fowler

I would say 14 volts should be around normal for a chevy charging system when running. Most makes of vehicles will charge at 14 volts or possibly higher I believe.
Anthony Morgan

Both pressure and voltage sound fine to me.
Derek Nicholson

I believe charging up to 17 volts is OK with a Delco. 14-16 is ideal. 12 is not enough. I put a voltmeter on my '73 B/GT when I added a Delco/Saturn alternator with about 100 amps output, and it usually indicates just a little over 14 volts when charging.

Your oil pressure is GREAT! It will probably drop a bit in extended driving, but you have plenty of leaway.

FWIW,
Allen
Allen Bachelder

Charging voltage should be 14.3v *minimum* at a light load, the original alts to drop down from this as the load is increased, more modern and higher output alts less so. In theory anything over 12.8v should be OK, but in practice if your battery goes flat enough to be unable to start the engine then once restarted the lower voltage won't put the full capacity back into the battery. Mercedes for a time were selecting alternators with high voltages in the 'normal' range of 14.3v to 14.7v as even 14.3v wasn't enough. The original dynamo 'normal' voltage range was 14.9v to 15.5v at low temperatures (when arguably there will be the greatest load on the electrics). Too high a voltage for too long will boil out the distilled water though, and I'd say 17v running voltage was significantly too high.

The big thing to bear in mind with voltmeters is where they are connected. At the alternator terminal they may well register 14.5v. Under a heavy electrical load this could well drop 2 or 3 tenths at the solenoid and battery, and progressively lower still at the ignition switch brown, white, and the fusebox white and green. A green circuit is the logical place to connect a voltmeter as it fused for safety and there are plenty of connections behind the dash, but can give as much as a couple of volts lower reading than at the battery, which is what is important. I think this artifically lower voltage is what leads people to want to replace the original alts. I ran a GT in all weathers with heated rear screen, twin electric fans and uprated headlights and never had a problem with charging. The voltmeter is another one of those gauges that can just give you something more to worry about when it isn't necessary.
Paul Hunt 2

This thread was discussed between 24/03/2007 and 25/03/2007

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