We've got '69 302 mustang engine in our 1950 F1 & we've been dead in the water looking for a temp sending unit that fits. Our Autometer gauge came with numerous
adapters but none fit the temperature sender hole in the 302. I'm starting to lose hair on this one & I don't have much left to lose. I'd prefer not to drill it out for a larger
size - worry about metal getting into the block. Any thoughts? I've tried (2) different adapters from on-line sources "3/8 in NPT" was too big. The old sender is long gone as it had some awful smelling mercury stuff inside & was destroyed by my 18 year old taking it out.

Ben in Austin
(The poor old truck isn't driveable with an unplugged hole for the temp sender).

 

Taking it out of where? The old sender as in the old sender in the original engine in the 50……. or from the 302?

Anyways what it sounds like is a mechanical (mercury filled) sealed sending unit that has a special bushing that screws into the engine then has a seat that the mechanical sending bulb is sealed with it’s own nut (see picture). To replace a mechanical with electric you have to remove the bushing seat to get to a standard pipe thread.
There are also mechanical gauge bushings with the seat in various block / head hole sizes.

mechanical temp gauge.jpg

 

We removed the sending unit from the 302 engine block & yes it was one of those old mercury filled units. The piece we took out of the hole looks like a bolt with threads on the outside & is hollow in the middle for the temp sensing piece. I'll try to upload a picture - the problem I'm having is finding something that fits the hole. All we took out of the hole was the threaded bolt looking thing similar to your picture - Is there another bushing in there that needs to come out?

Thx
Ben in Austin

 

You know Ray that's damn embarassing - You are correct we still had to get the
other piece out of the hole. Humble pie & schooled by a Canadian. I'll root for your hockey team next time.

Thx
Ben in Austin

 

So, question for you.

Are you trying to use your stock instrument panel gauge?

If so, you will need to install an IL6 6 volt sender and put a voltage reducer on teh back of the gauge.

But ALSO, you can use new mechanical gauge guts and install them in the case for your stock gauge, put on the stock face and install it in your inst. panel and no one will know the diff. You can do this with oil pressure too. Amps is ok as is. Gas will need the reducer.

I have a gallery with pictures and instructions - the step by step!

 

Hi Julie,
We inherited a pretty much non-functioning gauge set in the truck - No reliable temp, no gas level, voltage worked, no speedo, etc. This project is a family bonding experience - I took a backseat on gauge selection as my son Zack was very interested in the "style" of gauges & the look. Not much went into "how" it would work & not much knowledge was involved in mechanical vs. electrical gauges. Sooo what we have is a set of "street rod" classic style autometer "short switch?"electric gauges that we are trying to get functional.

The speedo didn't come with a sender so I'll need to order the sending piece for that one. The gas gauge sender didn't fit into the 6 hole slot on the tank so we picked up some sort of 5 hole adapter - not sure that one really works as the "fume" level
seems high in the cab. If anyone has experience with these adapters I'm all ears.

Slow but steady progress in Austin. We are open to guidance on getting the gauges all working - It's a 12 volt system.

Thx
Ben in Austin

 

LOL Gauges always seems to be a number of unexpected steps backwards. I used the adapter on the gas tank on my 55 and about all I can recommend is a good cork gasket - on both sides of the adaptor. (make sure your filler rubber hoses are ok too)

Oil pressure shouldn't be a problem as the pressure is consistent up into the hole of the sender.

Temp I think you have a handle on.

The secret to gauges is that you have to use the sender made for the gauge. Make sure they are circuit protected with a (3 amp) fuse and they are of course switched on with the ignition. So unless you have a fuse block that gets turned on with the key, you should be able to run the power for those right off the "ACC" post of the ignition switch to one gauge then bridge wires between the gauges to distribute power.

Power runs in one side of the gauge then out the other to the sender, then on to ground. It's pretty simple. Matched senders and gauges is the key.

 

Thanks Julie,
I really appreciate your thoughts on how to get the gauges to work - ex. I didn't know that you go to the ACC post of the ignition switch for power for the gauges. Not sure I know what it really looks like but we'll get under there & take a look tomorrow. The 3 amp fuses you mention for the gauges - are these to be in line gauges on the wire from the sender to the gauge? I think we will be good finishing out the water & oil temp gauges - Can you shed some light on the Speedo Sender? We didn't get one with our gauge package - Are there universal sending units? Where exactly do they fit?

Thx for your help - Gauges are new territory for us so we are learning as we stumble through the darkness. Would you add a tachometer to this? We have an automatic but it might be useful to know how hard the engine is working.

Thx

Ben in Austin