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Good morning all. I have a '40 Chevy street rod. I wish to replace the messed up dash with originals and, here's by worry, convert them to 12 volt. I know the fuel sender I need. I have the original speedo and gauge panel. How do I successfully convert the original gauges without torching the car? Thanks, Robert
 

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Doc here, :pimp:

The first thing you will need is a 12 to 6 Volt regulator For the gauge power. You Can buy these, ranging from $50 on down, or build your own for under $5, or scavenge one out of a 70's Ford or Dodge in the Bone yard.

If your gauges are different from stock NOW, you'll need to find the resistance value of the senders you have now..These must match the resistance value of the stock gauges for them to work and/or be accurate. So those may need changing.

If you have an AMP gauge , and are now running an Alternator, It is not going to work (Very long), as Generators were -30, 0, +30, and most Alternators are 64 amps or higher under full load. Additionally if the vehicle was positive ground, and you do try to use it, it will need to have the wires reversed, or it will indicate backwards..Best bet there (and much safer) disconnect it, and use a modern Volt gauge.

Don't forget to upgrade the panel lamps too.

Doc :pimp:
 

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The oil pressure guage is mechanical not electrical.

The maximum oil pressure in the old Chevy stovebolt engine was not very high so the existing guage may not be high enough for a full pressure lubricated engine.

Also, the water temperature guage is mechanical. This can be used as is, assuming it still works.

Immerse the sensor end of the guage capillary in some hot water and compare it with another guage and see is the old guage is close the same reading.

vicrod
 

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oil press on a 216 babbit engine ( what the car had originally, and what original gauge would read ) is 15 PSI at idle, and 25 -30 PSI at cruise speed, the gauge reads to just over 30 PSI. this gauge, you would need to have converted to read 60 PSI.
 

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vicrod said:
The oil pressure guage is mechanical not electrical.

Also, the water temperature guage is mechanical. .

vicrod
Doc here, :pimp:

Ooops! My bad... :sweat:

Forgot the Temp and Oil Gauge units were Capillary Type..( Been years since messing with a stocker that old..!) Thanks vicrod , for catching that! :thumbup:

So the only Electrical you'll be Concerned with, will be the Stock Fuel Gauge, and sender, and Clock (if you have one) .

The hardest part of this change looks to be getting the Bourden tubes out the firewall to the engine sender locations without kinking or breaking them.

Doc :pimp:
 

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docvette said:
Doc here, :pimp:

Ooops! My bad... :sweat:

Forgot the Temp and Oil Gauge units were Capillary Type..( Been years since messing with a stocker that old..!) Thanks vicrod , for catching that! :thumbup:

So the only Electrical you'll be Concerned with, will be the Stock Fuel Gauge, and sender, and Clock (if you have one) .

The hardest part of this change looks to be getting the Bourden tubes out the firewall to the engine sender locations without kinking or breaking them.

Doc :pimp:
clocks were windup in '40, unless it was a high end model, then it could have an automatic wind up, but for this function, a RUNTZ transistor would be just fine ( motor spins for about 60s once a day ).
 
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