Changing to "S" gauges on early car...easy?

[archtech]

I was liking the simple and more uniqueness of the simpler gauges of the "T" but I'm leaning toward more information. It this as easy as just replacing the gauge or do I have to change out the sending unit as well?

[sc_rufctr]

Depends on the year of your car... But yes it's doable.

Swapping gauges is easy and there's lots of info here on how to make things work in different cars.

There are some issues of making certain tachos work with different CDI units.
Also.. Do you have a mechanical speedo or electric?

What year is your car? Someone will chime in with more info specific to your car.

[Wilywilly]

It's best to change the sending units with the gauges, for example if the oil temp has numbers you will need a sender specfic for it and not for a gauge with bars. Senders are usually pretty cheap.

Bill

[archtech]

My car is a '71. Mostly looking for more info about the oil system. Tach, speedo, gas are fine. Looks like sending unit needs to be compatible with the gauge. I guess I'll have to wait till next oil change to switch out the sending units!

[Grady Clay]

It can be even more complex than that.

Look at the outboard side of your oil tank. Is there a bolt-on cover plate or just an indentation? If you have a cover plate, you only need an oil level sending unit. If only an indentation, you need a new or good used oil tank.

What year is your “T”? What engine (carb, MFI, CIS)? EDIT - aah '71.

For the oil pressure, you simply replace the oil pressure light switch with a VDO pressure sender.

The temperature gauge sender remains the same.

The ‘new’ gauges are: left –fuel level, oil level; 2nd left – oil temperature, oil pressure; center – tach; right center – speedometer; right – clock.

If you have a ’68 or ’69 “T”, you will want the screw-type instruments. If ’70 and later, all ‘push-in’ are the same. It is worth the time and effort to find the ‘just right’ parts for this.


There are some ‘clever’ improvements you can do in this process. Most notable are retaining the low oil pressure warning light, and using the early (’68) temperature sending unit and instrument. Even better is to have the temperature instrument from a ’68 Sportomatic calibrated with numbers but retaining the over-temperature warning light. You can mount the sender switch for that light on the ‘oil-out’ pipe from the engine.

The ’68 and earlier temperature sender and instrument has a full-scale range of 140F to 280F. The ’69-’76 sender and instrument are 120F to 300F and later (unmarked) are even greater range. The early version gives a wider swing of the indicator for a given temperature change. Very desirable.

I think Porsche went to the wider (higher) ranges and removed the markings so owners wouldn’t complain about high temperatures in the engine. There was a similar change in the low oil pressure warning light switch so the light would not be on at hot idle. (I have a 40 psi low pressure warning light switch on my 914-6 SCCA racer.)

To retain the low oil pressure warning light, use a VDO sender than has two terminals; one for the instrument and the other for the light. Make the Faston connectors different size or gender so future engine removal doesn’t get them mis-connected.

There is a later tach housing that has the extra light socket for the low oil pressure warning light. Depending on your year, you will need to have that tach housing used with your tach face and electronics. North Hollywood Speedometer can do that.

There is an aftermarket combination instrument that has three sections, like a Carrera 2 (356) and the 904. These are used by 914s and 914-6 to add to their 3-instrument dash. That is easily adapted to a 911 or 912.

There is a quartz clock that can be made to appear as original on earlier cars (except for the second hand if you want to retain it). (I have a little battery and diode [~40 g] so the clock remains uninterrupted when I disconnect the car battery. This should be built into a modified clock.)

I’ll encourage you to retain your ‘period correct’ instrument faces. I prefer the ’71 and earlier glass lenses.

All the wires are originally in the main wiring harness but unused (even the Sportomatic wire). You will find the wires for the oil level sender taped to the harness to the RR tail light assembly.

Best,
Grady

[djdsc]

Please correct me on this but I don't believe that the physical size of the gauge case changed from '70 on, but the hole size in the dash and the rubber trim ring changed for the "push in" gauges. I know that I adapted a later push in gauge to my '68 dash by simply adding the mounting studs to the back of the push in gauge and using the '68 rubber trim ring. I recall measuring the gauge case (VDO temp/oil pressure) and there being no difference.

[archtech]

Thanks so much for the help, guys! Very informative and just what I needed. I'll be looking for period correct gauges like you recommended... and yes the glass lenses...and with the silver center. I'll probably just switch out the oil pressure light to a gauge. Oil level I've heard wasnt that accurate and should probably stick with checking oil level periodically with the dipstick. Oil temperature I may change since the when the car is warm, the gauge still reads in the cool end of the gauge rather than middle. Not sure whats up with that, any idea?