Adapting An OE Gas Tank Sender Unit
 

This may be lengthy but may help someone. Have a 1947 long-door coupe. Installed new Bob Drake gas tank. Fit very well re size, shape and features of the OE tank EXCEPT the hole and steel collar for the tank sending unit is too small to use an OE sender unit :mad:. It's set-up to use their 12 volt sending unit. My car was previously converted to 12 volt and dash gauges had 12 to 6 volt reducers. My OE Ford sender unit worked fine and was very accurate. Their resistance-type 12 volt sender did not work correctly with my dash gauge.

Although the my OE sender's mounting screw holes matched their outer set and I could lower the OE sender arm and float into their tank, the bottom of my OE sender had to be about 3/8 inch above their collar hole. They correctly cautioned not to cut their collar hole larger because leakage could occur.

I figured a rather simple solution for myself. At hardware store bought a rubber gasket that goes between the toilet tank and toilet base - has a beveled edge on one side and typically they are all the same diameter. With a sharp knife I carefully trimmed the beveled edge off. This gave me the extra 3/8 inch of height I needed to attach the OE sender unit to tank collar. Using the thin rubber gasket they provided as a guide, I drilled holes thru the new 3/8 inch gasket for the attaching screws. Bought longer attaching screws (#10-32 x 3/4") .... Note that the screw holes in their tank collar are "dead-ended" to prevent leakage, so one must buy a specific screw length.
Installed the sender unit using Permatex Ultra Blue sealant (gas resistant) and grounded sender to frame. Sender and gauge work fine ;).

Re: Adapting An OE Gas Tank Sender Unit
 

DrB. Looks like a nice job. Did you check to see if the toilet gasket was fuel proof? The PO of my '46 Coupe use a gasket material that was not fuel proof, and it made a mess inside the tank. It took me hours to "fish" out the chunks of rubber that fell in. I was real lucky that none of the chunks got sucked into, or plugged the fuel pick-up tube while I was on the road.

Sorry I couldn't up load pics. I'll try later.

Re: Adapting An OE Gas Tank Sender Unit
 

Drbrown: Give yourself a gas tank merit badge as you did a great job
of solving a common problem. Well done. May I suggest that you run a ground wire from one of the screws on the sending unit to "ground" on the frame just as a precaution to ensure a good ground.
PS: There is a "spacer collar" available to also sove that problem.It has two sets of screw holes -one for the tank and another set for the OEM sending unit.
https://www.speedwaymotors.com/Speed...RoChhAQAvD_BwE

Re: Adapting An OE Gas Tank Sender Unit
 

I would keep a close watch for leaks. No way is a toilet seal going to last with today's fuel.

Re: Adapting An OE Gas Tank Sender Unit
 

Be careful, on my tudor 37 I made a rubber gasket between the sending unit and the tank. Some days later it was smelling gas in the car... the rubber was melt by gasoline...

Re: Adapting An OE Gas Tank Sender Unit
 

Dr. Finally got the pic of the rubber gasket loaded. All those little pieces were in the tank.

Re: Adapting An OE Gas Tank Sender Unit
 

First a slight Correction .... I used "Permatex Ultra Blue" sealant on the gasket surfaces (Prestone doesn't make such). Its a one-part sealant that sets up withing a few hours.
Used it before and not had leakage.

A positive aspect is that the sender unit gasket, in either stock or elevated position, is above the top of the tank. So unless one constantly over-fills the tank or drives a lot on hills and curved roads, the gasket connection should not get gas on it the majority of the time. Given my particular installation, I will be careful not to over fill the tank. If I did, at about 15 mpg I would just have to drive around town a bit for the level to drop down.

The toilet tank gasket I bought at Lowe's is black fairly firm rubber-like material; it does not compresses much. The gasket Bob Drake included looked to be the same material (black rubber - in photo). I've used Drake's gasket before and not had a disintegration problem.

19Forty: I used the ground wire that came with Drake's unit. During testing the fuel gauge worked even without it.

51Woodie: Regarding red-colored rubber gasket, I remember in early 1900's they made inner tubes out of that.

Re: Adapting An OE Gas Tank Sender Unit
 

You can buy rubber sheet and make your own gaskets. GARLOCK is a common manufacturer, although there are others. I bet you could also buy a small piece at a marine store. Power plants and city water plants have this also. Do you know anyone who works at these places?
https://www.google.com/search?q=garl...DwnFru_ToV-FKM

and

https://www.google.com/search?q=3%2F...hrome&ie=UTF-8

Re: Adapting An OE Gas Tank Sender Unit
 

Personally I'd never use any type of sealant in this area out of fear of it dislodging and falling in to the tank. That can cause catastrophic issues.

Drbrown... even though you are careful to not overfill your tank, what do you do about the fumes attacking all of that gunk?

Re: Adapting An OE Gas Tank Sender Unit
 

Back many years ago I had a PU truck that the previous owner used RTV gasket sealer on the fuel tank hose. The truck would shut down suddenly. after a few minutes it would start only to do the same thing again. I changed all the components that I thought would cause the shutdown to no avail. then one day it would not restart, i traced the problem to no fuel flow. Seems that a glob of RTV would get in the pick up line, then some fuel would back flush it out and it would flow again until it finally lodged in the pick line I spent a lot of aggravation finding the problem. I feel your in trouble because the rubber will not hold up, neither will the sealant. I have used a blue sealant used in the air conditioning trade that's not effected by gas. I would suggest you redo it with the proper materials and save yourself from a roadside dilemma. JMHO

Re: Adapting An OE Gas Tank Sender Unit
 

Seems someone should make an adapter that is the reverse of the one speedway motors sells, so you can use a modern tank and original KS sender. I like the corprene gasket shown in the link too.

Re: Adapting An OE Gas Tank Sender Unit
 

I had the same issue with my OEM sending unit fitting inside the collar hole of a new aftermarket steel tank on my 40. I trimmed the collar hole to allow the sender to drop down in to the collar ring as it was designed.

I then took the tank to my local radiator shop and had him solder the outer ring of the collar to the tank, this eliminates any possibility of a leak.

Re: Adapting An OE Gas Tank Sender Unit
 

Branded. Well done. Folks have to remember to do this before tank install so there are no surprises.

Re: Adapting An OE Gas Tank Sender Unit
 

Branded: I examined the steel collar on Bob Drakes sending unit hole and concluded the same. If I had cut the hole larger I would have gotten into the area where the collar was not fully welded to the tank body. Its impossible to find a welder in my small city, and when I did years ago, they would refuse to work on an item like a gas tank (liability) So its good to have such friends.

Sealant: I used the Permatex Ultra Blue sealant on my sender unit about 5 years ago when I had to replace the cork float on the sender unit arm. Its worked ok. The possibility of particles of the sealant getting into the fuel stream is well taken .... just have to be careful about not applying too much. When the Ultra Blue is cured, it has a very "elastic" quality and is tough to scrape off a metal surface. Bob Drake's gasket is rubber but instructions don't mention the use of a sealant. My OE gasket was set in some kind of sealant and I use sealant because of other discussions to do so.

Adapter: Ideally to would be good to have a metal spacer/adapter made by a machine shop - don't have them here anymore - then use a gasket each side.

Seems we all are having to become welders, metal fabricators, etc. .... dying arts.

Re: Adapting An OE Gas Tank Sender Unit
 

I did that last fall when I adapted a K-S sender into the TANKS poly tank in my '40. Not hard to do with a piece of alum. plate, a hole-saw and the correct counter-sinks. Worst part was making a new float arm and finding a float small enough to fit through the smaller hole in the tank. It's still not 100% accurate but works a lot better than the aftermarket senders I tried...

And I've used Hylomar as a sealant with no issues; doesn't get hard and is not affected by fuel.