Replacing Standard 911 Gauges With L or S Gauges

[68911USA]

Hello, everyone. I have a '68 911, USA version. It has the standard 911 gauges, and I have purchased correct fuel/oil level & oil temp/pressure gauges to install. (My old '68 911T Sportomatic had them, and I love the additional information you get.)

My question- I have not pulled the old gauges out, but are the connections the same on the back of the gauges? Will I need to change the oil pressure sending unit to work with them? Is there already a wire in the harness to hook up the oil tank level gauge that's just tied off somewhere behind the gauges?

The car is currently up on jack stands in the garage, I've pulled the brake calipers and rotors to replace them, and I'm noodling on a few other things this winter as well. My old Sportomatic also had vented discs, and this one has solid. Can I just replace them with stock type vented with no issues? It doesn't look any different, just thought I'd ask.

I just moved to TN from Colorado, and my Porsche buddies are 1000 miles away now, thanks for the help. I have a feeling I will be a heavy poster on the list!

[68911USA]

Hmm...found an old thread from 2003 that looks like I will need to confirm that my oil tank has a provision for the correct sender unit. Hope it does. The rest is still foggy.

[Grady Clay]

The Sportomatic temperature/pressure instrument is very desirable in one respect, it has provision for an over-temperature warning light. I recommend you have the face of the instrument with temperature calibrations as the ‘911S’ instruments from ‘65-‘68. Your instrument uses the temperature sending unit common from ’65-’68. This sending unit has the connection that pushes on axially. The wire for the sender is green/black. The later sending unit with the connection sliding on from the side will not work correctly.

You already discovered you need an oil tank with provision for the oil level sending unit. Many early tanks have a block-off plate installed when not using the oil level sender. You can use the oil tank from your Sportomatic. It will have provision for the level sender. You can easily seal off the two Sportomatic oil fittings using old CIS fuel line nuts.

The unused wire (green/white) for the oil level sender should be coiled up under the wiring harness near the oil filter console or tied up behind the right tail light assembly.

The oil pressure sending unit simply replaces your oil pressure switch on top of the engine near the crankcase breather. The wire for the spressure sending unit is green/red. Keep in mind these use straight threads (M10x1.5 mm) with a copper sealing washer and not ‘tapered pipe threads’. When fussing’ around here, the ‘while-you-are-there' things are the gasket for the breather plate, the sealing washer between the existing oil pressure sending unit adaptor and the crankcase and the thermostat O-ring. Also close are the three oil cooler seals.

Yes, there is the wire for the oil pressure sender in the wiring harness. In fact there is an extra wire used for the Sportomatic over-temperature warning light in the non-Sportomatic 911s. You can use this wire for an over-temperature warning light or for a low oil pressure warning light.

VDO makes an oil pressure sending unit that has two terminals, one for the analog pressure gauge and the other is a contact switch for a low oil pressure warning light.

An over-temperature warning light can be fitted to a non-Sportomatic 911 using your Sportomatic instrument. The sending switch can be a commercial ‘snap-action’ switch attached to the oil outlet from the engine. The oil filter console is a good location. This gives early warning of the actual oil temperature coming from the engine and not already cooled. The wire is the one used for the Sportomatic over-temperature sender (green, no tracer).

These instruments do not have a provision for using both an analog oil pressure gauge and a low oil pressure warning light as Porsche started using with the '74 model year. You can have the instrument modified for this feature when you have the temperature calibration numbers installed.

All the other electrical connections to the instruments are the same or are accessible behind the dash. The previously unused connections probably have the rubber covering extending past the end of the connector. Try trimming the covering back to the end of the connector with an X-acto knife. If any of the coverings are missing, you can use heat-shrink tubing as a substitute.

Best,
Grady

[Superman]

Could you be more specific, Grady?

[68911USA]

Thanks, Grady! I think for now I will just put in the Oil Temp/Pressure gauge and not worry about the fuel gauge. I am curious about the oil pressure, since the light on the bottom of my "standard" gauge currently installed doesn't light up at all, but the engine seems to run fine. It might even be something as simple as the bulb being out. Thanks again!

[Grady Clay]

To change subjects: re; converting 1968 to the vented brakes from the Sportomatic.

For reference, all Sportomatic 911s used the largest, best vented brakes available for that year production. For example a Sportomatic 911T was delivered with 911S brakes – say, ’73. The reason is there is less ‘trailing throttle’ compression braking with the Sportomatic. Porsche engineers felt the largest brakes (of the day) necessary.

Basically all you have to do is swap rotors and calipers. In the front and rear, there is a ‘dog-bone’ 2-hole spacer between the caliper and the training arms. The caliper attachment bolts are comparably longer. Be sure to include the spacers and proper length bolts.

The rotors bolt on with no change in hardware.

If you continue to use the 7 mm wheel spacers in the rear (standard ’68), the flat-head slotted bolts for the spacer and rotor are longer than earlier (’68 only bolts).

There isn’t any change in the parking brake system. This would also be a good opportunity to rehab this system. Basically only cleaning, plating and lubrication should be necessary. Use the best of the parking brake shoes and make sure they fit the radius of the drum in the rotor.

Be sure the calipers work correctly. Critical is the pistons don’t stick in the bores. Additionally check the pad return feature and the angle of the cut in the pistons. I would be reluctant to disassemble the calipers without knowing the repair parts are in hand. The “S” calipers are similar to the ‘normal’ calipers but have a spacer between the two halves of the caliper. These require an extra seal (or longer ones in some cases) between the caliper halves and the spacer. The OEM Ate kits used to have these (30-40 years ago). I don’t know about today.

This is the time to replace the master cylinder and all four flex brake hoses. I prefer the rubber OEM to any of the Teflon/stainless steel braid type. They give better feel with imperfect road surface, tires and rotors – even almost undetectable imperfections can have an effect at the limit of braking. Make sure your new dual master cylinder has compatible failure warning switch(es).

A worthwhile mod is to add the later brake fluid reservoir with the ‘low-fluid’ indicator. Wire that to the parking brake/master cylinder failure warning light.


More.
Have you considered installing a circulating fuel system with the fuel pump on the front cross member? How about H1 headlights and relays? Relays will greatly extend the life of the ignition switch, headlight switch and the hi-lo beam/turn signal switch as the full headlight current passes through all three. An important service item during your projects is to inspect, clean and possibly repair the busses on the backside of the fuse block.

Best,
Grady